1
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Li S, Wang R, Frauenheim T, He J. Optical-Helicity-Dependent Orbital and Spin Dynamics in Two-Dimensional Ferromagnets. J Phys Chem Lett 2024; 15:5939-5946. [PMID: 38810216 PMCID: PMC11163468 DOI: 10.1021/acs.jpclett.4c01152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 05/24/2024] [Accepted: 05/28/2024] [Indexed: 05/31/2024]
Abstract
Disentangling orbital (OAM) and spin (SAM) angular momenta in the ultrafast spin dynamics of two-dimensional (2D) ferromagnets on subfemtoseconds is a challenge in the field of ultrafast magnetism. Herein, we employed a non-collinear spin version of real-time time-dependent density functional theory to investigate the orbital and spin dynamics of the 2D ferromagnets Fe3GeTe2 (FGT) induced by circularly polarized light. Our results show that the demagnetization of the Fe sublattice in FGT is accompanied by helicity-dependent precession of the OAM and SAM excited by circularly polarized lasers. We further identify that precession of the OAM and SAM in FGT is faster than demagnetization within a few femtoseconds. Remarkably, circularly polarized lasers can significantly induce a periodic transverse linear response of the OAM and SAM on very ultrafast time scales of ∼600 attoseconds. Our finding suggests a powerful new route for attosecond regimes of the angular momentum manipulation to coherently control helicity-dependent orbital and spin dynamics in 2D ferromagnets.
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Affiliation(s)
- Shuo Li
- Institute
for Advanced Study, Chengdu University, Chengdu 610106, China
| | - Ran Wang
- Institute
for Advanced Study, Chengdu University, Chengdu 610106, China
| | - Thomas Frauenheim
- Institute
for Advanced Study, Chengdu University, Chengdu 610106, China
- School
of Science, Constructor University, Bremen 28759, Germany
| | - Junjie He
- Department
of Physical and Macromolecular Chemistry, Faculty of Science, Charles University, Prague 12843, Czech Republic
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2
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Li R, Rezaeiyan Y, Böhnert T, Schulman A, Ferreira R, Farkhani H, Moradi F. Temperature effect on a weighted vortex spin-torque nano-oscillator for neuromorphic computing. Sci Rep 2024; 14:10043. [PMID: 38698145 PMCID: PMC11065860 DOI: 10.1038/s41598-024-60929-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 04/26/2024] [Indexed: 05/05/2024] Open
Abstract
In this work, we present fabricated magnetic tunnel junctions (MTJs) that can serve as magnetic memories (MMs) or vortex spin-torque nano-oscillators (STNOs) depending on the device geometry. We explore the heating effect on the devices to study how the performance of a neuromorphic computing system (NCS) consisting of MMs and STNOs can be enhanced by temperature. We further applied a neural network for waveform classification applications. The resistance of MMs represents the synaptic weights of the NCS, while temperature acts as an extra degree of freedom in changing the weights and TMR, as their anti-parallel resistance is temperature sensitive, and parallel resistance is temperature independent. Given the advantage of using heat for such a network, we envision using a vertical-cavity surface-emitting laser (VCSEL) to selectively heat MMs and/or STNO when needed. We found that when heating MMs only, STNO only, or both MMs and STNO, from 25 to 75 °C, the output power of the STNO increases by 24.7%, 72%, and 92.3%, respectively. Our study shows that temperature can be used to improve the output power of neural networks, and we intend to pave the way for future implementation of a low-area and high-speed VCSEL-assisted spintronic NCS.
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Affiliation(s)
- Ren Li
- Department of Electrical and Computer Engineering, Aarhus University, 8200, Aarhus, Denmark.
| | - Yasser Rezaeiyan
- Department of Electrical and Computer Engineering, Aarhus University, 8200, Aarhus, Denmark
| | - Tim Böhnert
- INL-International Iberian Nanotechnology Laboratory, 4715-330, Braga, Portugal
| | - Alejandro Schulman
- INL-International Iberian Nanotechnology Laboratory, 4715-330, Braga, Portugal
| | - Ricardo Ferreira
- INL-International Iberian Nanotechnology Laboratory, 4715-330, Braga, Portugal
| | - Hooman Farkhani
- Department of Electrical and Computer Engineering, Aarhus University, 8200, Aarhus, Denmark
| | - Farshad Moradi
- Department of Electrical and Computer Engineering, Aarhus University, 8200, Aarhus, Denmark.
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3
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Yang B, Ji Q, Huang FZ, Li J, Tian YZ, Xue B, Zhu R, Wu H, Yang H, Yang YB, Tang S, Zhao HB, Cao Y, Du J, Wang BG, Zhang C, Wu D. Picosecond Spin Current Generation from Vicinal Metal-Antiferromagnetic Insulator Interfaces. PHYSICAL REVIEW LETTERS 2024; 132:176703. [PMID: 38728713 DOI: 10.1103/physrevlett.132.176703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 03/22/2024] [Indexed: 05/12/2024]
Abstract
We report the picosecond spin current generation from the interface between a heavy metal and a vicinal antiferromagnet insulator Cr_{2}O_{3} by laser pulses at room temperature and zero magnetic field. It is converted into a detectable terahertz emission in the heavy metal via the inverse spin Hall effect. The vicinal interfaces are apparently the source of the picosecond spin current, as evidenced by the proportional terahertz signals to the vicinal angle. We attribute the origin of the spin current to the transient magnetic moment generated by an interfacial nonlinear magnetic-dipole difference-frequency generation. We propose a model based on the in-plane inversion symmetry breaking to quantitatively explain the terahertz intensity with respect to the angles of the laser polarization and the film azimuth. Our work opens new opportunities in antiferromagnetic and ultrafast spintronics by considering symmetry breaking.
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Affiliation(s)
- B Yang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Qing Ji
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - F Z Huang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Jiacong Li
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Y Z Tian
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - B Xue
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Ruxian Zhu
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Hui Wu
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Hanyue Yang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Y B Yang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Shaolong Tang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - H B Zhao
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433, People's Republic of China
| | - Y Cao
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - J Du
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - B G Wang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Chunfeng Zhang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - D Wu
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
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4
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Pankratova M, Miranda IP, Thonig D, Pereiro M, Sjöqvist E, Delin A, Scheid P, Eriksson O, Bergman A. Coupled atomistic spin-lattice simulations of ultrafast demagnetization in 3d ferromagnets. Sci Rep 2024; 14:8138. [PMID: 38584162 PMCID: PMC10999457 DOI: 10.1038/s41598-024-58662-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 04/02/2024] [Indexed: 04/09/2024] Open
Abstract
Despite decades of research, the role of the lattice and its coupling to the magnetisation during ultrafast demagnetisation processes is still not fully understood. Here we report on studies of both explicit and implicit lattice effects on laser induced ultrafast demagnetisation of bcc Fe and fcc Co. We do this using atomistic spin- and lattice dynamics simulations following a heat-conserving three-temperature model. We show that this type of Langevin-based simulation is able to reproduce observed trends of the ultrafast magnetization dynamics of fcc Co and bcc Fe. The parameters used in our models are all obtained from electronic structure theory, with the exception of the lattice dynamics damping term, where a range of parameters were investigated. It was found that while the explicit spin-lattice coupling in the studied systems does not impact the demagnetisation process notably, the lattice damping has a large influence on the details of the magnetization dynamics. The dynamics of Fe and Co following the absorption of a femtosecond laser pulse are compared with previous results for Ni and similarities and differences in the materials' behavior are analysed. For all elements investigated so far with this model, we obtain a linear relationship between the value of the maximally demagnetized state and the fluence of the laser pulse , which is in agreement with experiments. Moreover, we demonstrate that the demagnetization amplitude is largest for Ni and smallest for Co. This holds over a wide range of the reported electron-phonon couplings, and this demagnetization trend is in agreement with recent experiments.
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Affiliation(s)
- M Pankratova
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - I P Miranda
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - D Thonig
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
- School of Science and Technology, Örebro University, 701 82, Örebro, Sweden
| | - M Pereiro
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - E Sjöqvist
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - A Delin
- Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, AlbaNova University Center, 10691, Stockholm, Sweden
- Swedish e-Science Research Center (SeRC), KTH Royal Institute of Technology, 10044, Stockholm, Sweden
- Wallenberg Initiative Materials Science for Sustainability (WISE), KTH Royal Institute of Technology, 10044, Stockholm, Sweden
| | - P Scheid
- LPCT, CNRS, UMR 7019, BP 70239, Université de Lorraine, 54506, Vandoeuvre-lés-Nancy Cedex, France
- IJL, CNRS, UMR 7198, BP 70239, Université de Lorraine, 54000, Nancy Cedex, France
| | - O Eriksson
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
- Wallenberg Initiative Materials Science for Sustainability, Uppsala University, 75121, Uppsala, Sweden
| | - A Bergman
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
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5
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Fang N, Wu C, Zhang Y, Li Z, Zhou Z. Perspectives: Light Control of Magnetism and Device Development. ACS NANO 2024; 18:8600-8625. [PMID: 38469753 DOI: 10.1021/acsnano.3c13002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Accurately controlling magnetic and spin states presents a significant challenge in spintronics, especially as demands for higher data storage density and increased processing speeds grow. Approaches such as light control are gradually supplanting traditional magnetic field methods. Traditionally, the modulation of magnetism was predominantly achieved through polarized light with the help of ultrafast light technologies. With the growing demand for energy efficiency and multifunctionality in spintronic devices, integrating photovoltaic materials into magnetoelectric systems has introduced more physical effects. This development suggests that sunlight will play an increasingly pivotal role in manipulating spin orientation in the future. This review introduces and concludes the influence of various light types on magnetism, exploring mechanisms such as magneto-optical (MO) effects, light-induced magnetic phase transitions, and spin photovoltaic effects. This review briefly summarizes recent advancements in the light control of magnetism, especially sunlight, and their potential applications, providing an optimistic perspective on future research directions in this area.
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Affiliation(s)
- Ning Fang
- School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China
| | - Changqing Wu
- School of Environmental Science and Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Yuzhe Zhang
- School of Environmental Science and Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Zhongyu Li
- School of Environmental Science and Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Ziyao Zhou
- School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China
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6
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Gajapathy H, Bandaranayake S, Hruska E, Vadakkayil A, Bloom BP, Londo S, McClellan J, Guo J, Russell D, de Groot FMF, Yang F, Waldeck DH, Schultze M, Baker LR. Spin polarized electron dynamics enhance water splitting efficiency by yttrium iron garnet photoanodes: a new platform for spin selective photocatalysis. Chem Sci 2024; 15:3300-3310. [PMID: 38425509 PMCID: PMC10901523 DOI: 10.1039/d3sc03016d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 01/16/2024] [Indexed: 03/02/2024] Open
Abstract
This work presents a spectroscopic and photocatalytic comparison of water splitting using yttrium iron garnet (Y3Fe5O12, YIG) and hematite (α-Fe2O3) photoanodes. Despite similar electronic structures, YIG significantly outperforms widely studied hematite, displaying more than an order of magnitude increase in photocurrent density. Probing the charge and spin dynamics by ultrafast, surface-sensitive XUV spectroscopy reveals that the enhanced performance arises from (1) reduced polaron formation in YIG compared to hematite and (2) an intrinsic spin polarization of catalytic photocurrents in YIG. Ultrafast XUV measurements show a reduction in the formation of surface electron polarons compared to hematite due to site-dependent electron-phonon coupling. This leads to spin polarized photocurrents in YIG where efficient charge separation occurs on the Td sub-lattice compared to fast trapping and electron/hole pair recombination on the Oh sub-lattice. These lattice-dependent dynamics result in a long-lived spin aligned hole population at the YIG surface, which is directly observed using XUV magnetic circular dichroism. Comparison of the Fe M2,3 and O L1-edges show that spin aligned holes are hybridized between O 2p and Fe 3d valence band states, and these holes are responsible for highly efficient, spin selective water oxidation by YIG. Together, these results point to YIG as a new platform for highly efficient, spin selective photocatalysis.
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Affiliation(s)
- Harshad Gajapathy
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA
| | - Savini Bandaranayake
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA
| | - Emily Hruska
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA
| | - Aravind Vadakkayil
- Department of Chemistry, University of Pittsburgh 15260 Pittsburgh Pennsylvania USA
| | - Brian P Bloom
- Department of Chemistry, University of Pittsburgh 15260 Pittsburgh Pennsylvania USA
| | - Stephen Londo
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA
| | - Jackson McClellan
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA
| | - Jason Guo
- Department of Physics, The Ohio State University Columbus Ohio 43210 USA
| | - Daniel Russell
- Department of Physics, The Ohio State University Columbus Ohio 43210 USA
| | - Frank M F de Groot
- Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University 3584CG Utrecht The Netherlands
| | - Fengyuan Yang
- Department of Physics, The Ohio State University Columbus Ohio 43210 USA
| | - David H Waldeck
- Department of Chemistry, University of Pittsburgh 15260 Pittsburgh Pennsylvania USA
| | - Martin Schultze
- Institute of Experimental Physics, Graz University of Technology Petersgasse 16 Graz 8010 Austria
| | - L Robert Baker
- Department of Chemistry and Biochemistry, The Ohio State University Columbus Ohio 43210 USA
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7
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Jangid R, Hagström NZ, Madhavi M, Rockwell K, Shaw JM, Brock JA, Pancaldi M, De Angelis D, Capotondi F, Pedersoli E, Nembach HT, Keller MW, Bonetti S, Fullerton EE, Iacocca E, Kukreja R, Silva TJ. Extreme Domain Wall Speeds under Ultrafast Optical Excitation. PHYSICAL REVIEW LETTERS 2023; 131:256702. [PMID: 38181360 DOI: 10.1103/physrevlett.131.256702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/05/2023] [Accepted: 11/08/2023] [Indexed: 01/07/2024]
Abstract
Time-resolved ultrafast EUV magnetic scattering was used to test a recent prediction of >10 km/s domain wall speeds by optically exciting a magnetic sample with a nanoscale labyrinthine domain pattern. Ultrafast distortion of the diffraction pattern was observed at markedly different timescales compared to the magnetization quenching. The diffraction pattern distortion shows a threshold dependence with laser fluence, not seen for magnetization quenching, consistent with a picture of domain wall motion with pinning sites. Supported by simulations, we show that a speed of ≈66 km/s for highly curved domain walls can explain the experimental data. While our data agree with the prediction of extreme, nonequilibrium wall speeds locally, it differs from the details of the theory, suggesting that additional mechanisms are required to fully understand these effects.
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Affiliation(s)
- Rahul Jangid
- Department of Materials Science and Engineering, University of California Davis, Davis, California, USA
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Nanna Zhou Hagström
- Department of Materials Science and Engineering, University of California Davis, Davis, California, USA
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
| | - Meera Madhavi
- Department of Materials Science and Engineering, University of California Davis, Davis, California, USA
| | - Kyle Rockwell
- Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, Colorado Springs, Colorado, USA
| | - Justin M Shaw
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado, USA
| | - Jeffrey A Brock
- Center for Memory and Recording Research, University of California San Diego, La Jolla, California, USA
| | - Matteo Pancaldi
- Elettra Sincrotrone Trieste S.C.p.A., Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Dario De Angelis
- Elettra Sincrotrone Trieste S.C.p.A., Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Flavio Capotondi
- Elettra Sincrotrone Trieste S.C.p.A., Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Emanuele Pedersoli
- Elettra Sincrotrone Trieste S.C.p.A., Area Science Park, S.S. 14 km 163.5, 34149 Trieste, Italy
| | - Hans T Nembach
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
- Associate, Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
| | - Mark W Keller
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado, USA
| | - Stefano Bonetti
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, 30172 Venezia, Italy
| | - Eric E Fullerton
- Center for Memory and Recording Research, University of California San Diego, La Jolla, California, USA
| | - Ezio Iacocca
- Center for Magnetism and Magnetic Nanostructures, University of Colorado Colorado Springs, Colorado Springs, Colorado, USA
| | - Roopali Kukreja
- Department of Materials Science and Engineering, University of California Davis, Davis, California, USA
| | - Thomas J Silva
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado, USA
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8
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Chen Z, Luo JW, Wang LW. Light-induced ultrafast spin transport in multilayer metallic films originates from sp- d spin exchange coupling. SCIENCE ADVANCES 2023; 9:eadi1618. [PMID: 38100591 PMCID: PMC10848703 DOI: 10.1126/sciadv.adi1618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 11/15/2023] [Indexed: 12/17/2023]
Abstract
Ultrafast interaction between the femtosecond laser pulse and the magnetic metal provides an efficient way to manipulate the magnetic states of matter. Numerous experimental advancements have been made on multilayer metallic films in the last two decades. However, the underlying physics remains unclear. Here, relying on an efficient ab initio spin dynamics simulation algorithm, we revealed the physics that can unify the progress in different experiments. We found that light-induced ultrafast spin transport in multilayer metallic films originates from the sp-d spin-exchange interaction, which can induce an ultrafast, large, and pure spin current from ferromagnetic metal to nonmagnetic metal without charge carrier transport. The resulting trends of spin demagnetization and spin flow are consistent with most experiments. It can explain a variety of ultrafast light-spin manipulation experiments with different systems and different pump-probe technologies, covering a wide range of work in this field.
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Affiliation(s)
- Zhanghui Chen
- Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
- Materials Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Mail Stop 50F, Berkeley, CA 94720, USA
- University of Chinese Academy of Sciences, No.1 Yanqihu East Rd, Huairou District, Beijing 101408, China
| | - Jun-Wei Luo
- Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
- University of Chinese Academy of Sciences, No.1 Yanqihu East Rd, Huairou District, Beijing 101408, China
| | - Lin-Wang Wang
- Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
- Materials Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Mail Stop 50F, Berkeley, CA 94720, USA
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9
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Ilyakov I, Brataas A, de Oliveira TVAG, Ponomaryov A, Deinert JC, Hellwig O, Faßbender J, Lindner J, Salikhov R, Kovalev S. Efficient ultrafast field-driven spin current generation for spintronic terahertz frequency conversion. Nat Commun 2023; 14:7010. [PMID: 37919284 PMCID: PMC10622539 DOI: 10.1038/s41467-023-42845-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 10/24/2023] [Indexed: 11/04/2023] Open
Abstract
Efficient generation and control of spin currents launched by terahertz (THz) radiation with subsequent ultrafast spin-to-charge conversion is the current challenge for the next generation of high-speed communication and data processing units. Here, we demonstrate that THz light can efficiently drive coherent angular momentum transfer in nanometer-thick ferromagnet/heavy-metal heterostructures. This process is non-resonant and does neither require external magnetic fields nor cryogenics. The efficiency of this process is more than one order of magnitude higher as compared to the recently observed THz-induced spin pumping in MnF2 antiferromagnet. The coherently driven spin currents originate from the ultrafast spin Seebeck effect, caused by a THz-induced temperature imbalance in electronic and magnonic temperatures and fast relaxation of the electron-phonon system. Owing to the fact that the electron-phonon relaxation time is comparable with the period of a THz wave, the induced spin current results in THz second harmonic generation and THz optical rectification, providing a spintronic basis for THz frequency mixing and rectifying components.
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Affiliation(s)
- Igor Ilyakov
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany.
| | - Arne Brataas
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway
| | | | - Alexey Ponomaryov
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany
| | - Jan-Christoph Deinert
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany
| | - Olav Hellwig
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany
- Institute of Physics, Chemnitz University of Technology, 09107, Chemnitz, Germany
| | - Jürgen Faßbender
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany
- Institute of Solid State and Materials Physics, Technische Universität Dresden, 01062, Dresden, Germany
| | - Jürgen Lindner
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany
| | - Ruslan Salikhov
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany.
| | - Sergey Kovalev
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328, Dresden, Germany.
- Technische Universität Dortmund, 44227, Dortmund, Germany.
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10
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Song Y, Ji Z, Zhang Y, Song Y, Li Z, Zhang J, Zhang J, Jiang Z, Liu Y, Jin Q, Zhang Z. High Efficiency and Flexible Modulation of Spintronic Terahertz Emitters in Synthetic Antiferromagnets. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37883114 DOI: 10.1021/acsami.3c11533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2023]
Abstract
Spintronic terahertz (THz) emitters based on synthetic antiferromagnets (SAFs) of FM1/Ru/FM2 (FM: ferromagnet) have shown great potential for achieving coherent superposition and significant THz power enhancement due to antiparallel magnetization alignment. However, key issues regarding the effects of interlayer exchange coupling and net magnetization on THz emissions remain unclear, which will inevitably hinder the performance improvement and practical application of THz devices. In this work, we have investigated the femtosecond laser-induced THz emission in Pt (3)/CoFe (3)/Ru (tRu = 0-3.5)/CoFe (tCoFe = 1.5-10)/Pt (3) (in units of nm) films with compensated and uncompensated magnetic moments. Antiferromagnetic (AF) coupling occurs in the Ru thickness ranges of 0.2-1.1 and 1.9-2.3 nm, with the first peak (tRu = 0.4 nm) of the AF coupling field (Hex) significantly higher than that of the second peak (2.0 nm). Rather high THz amplitude is found for the samples with strong AF coupling. Nevertheless, despite the same remanence ratio of zero, the THz amplitude for the symmetric SAF films declines significantly as the tRu decreases from 0.8 to 0.4 nm, which is mainly ascribed to the noncolinear magnetization vectors due to the increased biquadratic coupling term. Specifically, we demonstrate that an asymmetric SAF structure with a dominant FM layer is more favored than the completely compensated one, which could generate significantly enhanced THz electric field with well-controlled polarity and intensity. In addition, as the temperature decreases, the THz emission intensity increases for the SAF samples of tRu = 0.9 nm with negligible biquadratic coupling, which is contrary to the decreasing trend of the tRu = 0.4 nm sample and has been attributed to the greatly enhanced Hex.
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Affiliation(s)
- Yiwen Song
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Zhihao Ji
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Yu Zhang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Yuna Song
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Ziyang Li
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Jingying Zhang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Jiali Zhang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Zhiyao Jiang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Yaowen Liu
- School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Qingyuan Jin
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
| | - Zongzhi Zhang
- Shanghai Ultra-Precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (MOE), School of Information Science and Technology, Fudan University, Shanghai 200433, China
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11
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Paries F, Tiercelin N, Lezier G, Vanwolleghem M, Selz F, Syskaki MA, Kammerbauer F, Jakob G, Jourdan M, Kläui M, Kaspar Z, Kampfrath T, Seifert TS, von Freymann G, Molter D. Fiber-tip spintronic terahertz emitters. OPTICS EXPRESS 2023; 31:30884-30893. [PMID: 37710621 DOI: 10.1364/oe.494623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 07/27/2023] [Indexed: 09/16/2023]
Abstract
Spintronic terahertz emitters promise terahertz sources with an unmatched broad frequency bandwidth that are easy to fabricate and operate, and therefore easy to scale at low cost. However, current experiments and proofs of concept rely on free-space ultrafast pump lasers and rather complex benchtop setups. This contrasts with the requirements of widespread industrial applications, where robust, compact, and safe designs are needed. To meet these requirements, we present a novel fiber-tip spintronic terahertz emitter solution that allows spintronic terahertz systems to be fully fiber-coupled. Using single-mode fiber waveguiding, the newly developed solution naturally leads to a simple and straightforward terahertz near-field imaging system with a 90%-10% knife-edge-response spatial resolution of 30 µm.
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12
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Xie Z, Cai Y, Tang M, Zhou J, Liu J, Peng J, Jiang T, Shi Z, Chen Z. Fluence and Temperature Dependences of Laser-Induced Ultrafast Demagnetization and Recovery Dynamics in L1 0-FePt Thin Film. MATERIALS (BASEL, SWITZERLAND) 2023; 16:5086. [PMID: 37512360 PMCID: PMC10385860 DOI: 10.3390/ma16145086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 07/08/2023] [Accepted: 07/17/2023] [Indexed: 07/30/2023]
Abstract
The fundamental mechanisms of ultrafast demagnetization and magnetization recovery processes in ferromagnetic materials remain incompletely understood. The investigation of different dynamic features which depend on various physical quantities requires a more systematic approach. Here, the femtosecond laser-induced demagnetization and recovery dynamics in L10-Fe0.5Pt0.5 alloy film are studied by utilizing time-resolved magneto-optical Kerr measurements, focusing on their dependences of excitation fluence and ambient temperature over broad ranges. Ultrafast demagnetization dominated by Elliott-Yafet spin-flip scattering, and two-step magnetization recovery processes are found to be involved in all observations. The fast recovery time corresponding to spin-lattice relaxation is much shorter than that of many ferromagnets and increase with excitation fluence. These can be ascribed to the strong spin-orbit coupling (SOC) demonstrated in FePt and the reduction of transient magnetic anisotropy, respectively. Surprisingly, the demagnetization time exhibits no discernible correlation with ambient temperature. Two competitive factors are proposed to account for this phenomenon. On the other hand, the spin-lattice relaxation accelerates as temperature decreases due to enhanced SOC at lower ambient temperature. A semiquantitative analysis is given to get a visualized understanding. These results offer a comprehensive understanding of the dynamic characteristics of ultrafast demagnetization and recovery processes in iron-based materials with strong SOC, highlighting the potential for regulating the magnetization recovery process through temperature and laser fluence adjustments.
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Affiliation(s)
- Zhikun Xie
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
- State-Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Yuanhai Cai
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Meng Tang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Jielin Zhou
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Junhao Liu
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Jun Peng
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
| | - Tianran Jiang
- State-Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Zhong Shi
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Zhifeng Chen
- School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China
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13
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Kang K, Omura H, Yesudas D, Lee O, Lee KJ, Lee HW, Taniyama T, Choi GM. Spin current driven by ultrafast magnetization of FeRh. Nat Commun 2023; 14:3619. [PMID: 37385983 DOI: 10.1038/s41467-023-39103-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 05/30/2023] [Indexed: 07/01/2023] Open
Abstract
Laser-induced ultrafast demagnetization is an important phenomenon that probes arguably the ultimate limits of the angular momentum dynamics in solid. Unfortunately, many aspects of the dynamics remain unclear except that the demagnetization transfers the angular momentum eventually to the lattice. In particular, the role and origin of electron-carried spin currents in the demagnetization process are debated. Here we experimentally probe the spin current in the opposite phenomenon, i.e., laser-induced ultrafast magnetization of FeRh, where the laser pump pulse initiates the angular momentum build-up rather than its dissipation. Using the time-resolved magneto-optical Kerr effect, we directly measure the ultrafast-magnetization-driven spin current in a FeRh/Cu heterostructure. A strong correlation between the spin current and the magnetization dynamics of FeRh is found even though the spin filter effect is negligible in this opposite process. This result implies that the angular momentum build-up is achieved by an angular momentum transfer from the electron bath (supplier) to the magnon bath (receiver) and followed by the spatial transport of angular momentum (spin current) and dissipation of angular momentum to the phonon bath (spin relaxation).
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Affiliation(s)
- Kyuhwe Kang
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Korea
| | - Hiroki Omura
- Department of Physics, Nagoya University, Nagoya, 464-8602, Japan
| | - Daniel Yesudas
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Korea
| | - OukJae Lee
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Korea
| | - Kyung-Jin Lee
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon, 34141, Korea
| | - Hyun-Woo Lee
- Department of Physics, Pohang University of Science and Technology, Pohang, 37673, Korea
| | | | - Gyung-Min Choi
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Korea.
- Center for Integrated Nanostructure Physics, Institute for Basic Science, Suwon, 16419, Korea.
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14
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Mattern M, von Reppert A, Zeuschner SP, Herzog M, Pudell JE, Bargheer M. Concepts and use cases for picosecond ultrasonics with x-rays. PHOTOACOUSTICS 2023; 31:100503. [PMID: 37275326 PMCID: PMC10238750 DOI: 10.1016/j.pacs.2023.100503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 04/28/2023] [Accepted: 04/30/2023] [Indexed: 06/07/2023]
Abstract
This review discusses picosecond ultrasonics experiments using ultrashort hard x-ray probe pulses to extract the transient strain response of laser-excited nanoscopic structures from Bragg-peak shifts. This method provides direct, layer-specific, and quantitative information on the picosecond strain response for structures down to few-nm thickness. We model the transient strain using the elastic wave equation and express the driving stress using Grüneisen parameters stating that the laser-induced stress is proportional to energy density changes in the microscopic subsystems of the solid, i.e., electrons, phonons and spins. The laser-driven strain response can thus serve as an ultrafast proxy for local energy-density and temperature changes, but we emphasize the importance of the nanoscale morphology for an accurate interpretation due to the Poisson effect. The presented experimental use cases encompass ultrathin and opaque metal-heterostructures, continuous and granular nanolayers as well as negative thermal expansion materials, that each pose a challenge to established all-optical techniques.
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Affiliation(s)
- Maximilian Mattern
- Institut für Physik & Astronomie, Universität Potsdam, 14476 Potsdam, Germany
| | | | - Steffen Peer Zeuschner
- Institut für Physik & Astronomie, Universität Potsdam, 14476 Potsdam, Germany
- Helmholtz Zentrum Berlin, 12489 Berlin, Germany
| | - Marc Herzog
- Institut für Physik & Astronomie, Universität Potsdam, 14476 Potsdam, Germany
| | - Jan-Etienne Pudell
- Institut für Physik & Astronomie, Universität Potsdam, 14476 Potsdam, Germany
- Helmholtz Zentrum Berlin, 12489 Berlin, Germany
- European XFEL, 22869 Schenefeld, Germany
| | - Matias Bargheer
- Institut für Physik & Astronomie, Universität Potsdam, 14476 Potsdam, Germany
- Helmholtz Zentrum Berlin, 12489 Berlin, Germany
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15
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Liu B, Xiao H, Weinelt M. Microscopic insights to spin transport-driven ultrafast magnetization dynamics in a Gd/Fe bilayer. SCIENCE ADVANCES 2023; 9:eade0286. [PMID: 37196076 DOI: 10.1126/sciadv.ade0286] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 04/13/2023] [Indexed: 05/19/2023]
Abstract
Laser-induced spin transport is a key ingredient in ultrafast spin dynamics. However, it remains debated to what extent ultrafast magnetization dynamics generates spin currents and vice versa. We use time- and spin-resolved photoemission spectroscopy to study an antiferromagnetically coupled Gd/Fe bilayer, a prototype system for all-optical switching. Spin transport leads to an ultrafast drop of the spin polarization at the Gd surface, demonstrating angular-momentum transfer over several nanometers. Thereby, Fe acts as spin filter, absorbing spin majority but reflecting spin minority electrons. Spin transport from Gd to Fe was corroborated by an ultrafast increase of the Fe spin polarization in a reversed Fe/Gd bilayer. In contrast, for a pure Gd film, spin transport into the tungsten substrate can be neglected, as spin polarization stays constant. Our results suggest that ultrafast spin transport drives the magnetization dynamics in Gd/Fe and reveal microscopic insights into ultrafast spin dynamics.
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Affiliation(s)
- Bo Liu
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Huijuan Xiao
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Martin Weinelt
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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16
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Mottamchetty V, Rani P, Brucas R, Rydberg A, Svedlindh P, Gupta R. Direct evidence of terahertz emission arising from anomalous Hall effect. Sci Rep 2023; 13:5988. [PMID: 37045934 PMCID: PMC10097872 DOI: 10.1038/s41598-023-33143-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 04/07/2023] [Indexed: 04/14/2023] Open
Abstract
A detailed understanding of the different mechanisms being responsible for terahertz (THz) emission in ferromagnetic (FM) materials will aid in designing efficient THz emitters. In this report, we present direct evidence of THz emission from single layer Co[Formula: see text]Fe[Formula: see text]B[Formula: see text] (CoFeB) FM thin films. The dominant mechanism being responsible for the THz emission is the anomalous Hall effect (AHE), which is an effect of a net backflow current in the FM layer created by the spin polarized current reflected at the interfaces of the FM layer. The THz emission from the AHE-based CoFeB emitter is optimized by varying its thickness, orientation, and pump fluence of the laser beam. Results from electrical transport measurements show that skew scattering of charge carriers is responsible for the THz emission in the CoFeB AHE-based THz emitter.
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Affiliation(s)
- Venkatesh Mottamchetty
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03, Uppsala, Sweden
| | - Parul Rani
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - Rimantas Brucas
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03, Uppsala, Sweden
| | - Anders Rydberg
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03, Uppsala, Sweden
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - Peter Svedlindh
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03, Uppsala, Sweden.
| | - Rahul Gupta
- Department of Materials Science and Engineering, Uppsala University, Box 35, 751 03, Uppsala, Sweden.
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
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17
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Matsuda T, Higo T, Koretsune T, Kanda N, Hirai Y, Peng H, Matsuo T, Yoshikawa N, Shimano R, Nakatsuji S, Matsunaga R. Ultrafast Dynamics of Intrinsic Anomalous Hall Effect in the Topological Antiferromagnet Mn_{3}Sn. PHYSICAL REVIEW LETTERS 2023; 130:126302. [PMID: 37027855 DOI: 10.1103/physrevlett.130.126302] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 02/06/2023] [Indexed: 06/19/2023]
Abstract
We investigate ultrafast dynamics of the anomalous Hall effect (AHE) in the topological antiferromagnet Mn_{3}Sn with sub-100 fs time resolution. Optical pulse excitations largely elevate the electron temperature up to 700 K, and terahertz probe pulses clearly resolve ultrafast suppression of the AHE before demagnetization. The result is well reproduced by microscopic calculation of the intrinsic Berry-curvature mechanism while the extrinsic contribution is clearly excluded. Our work opens a new avenue for the study of nonequilibrium AHE to identify the microscopic origin by drastic control of the electron temperature by light.
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Affiliation(s)
- Takuya Matsuda
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Tomoya Higo
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | | | - Natsuki Kanda
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yoshua Hirai
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Hanyi Peng
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Takumi Matsuo
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Naotaka Yoshikawa
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Ryo Shimano
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Cryogenic Research Center, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0032, Japan
| | - Satoru Nakatsuji
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Trans-scale Quantum Science Institute, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
- Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, 21218 Maryland, USA
| | - Ryusuke Matsunaga
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Trans-scale Quantum Science Institute, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
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18
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Mukhopadhyay S, Majumder S, Narayan Panda S, Barman A. Investigation of ultrafast demagnetization and Gilbert damping and their correlation in different ferromagnetic thin films grown under identical conditions. NANOTECHNOLOGY 2023; 34:235702. [PMID: 36863009 DOI: 10.1088/1361-6528/acc079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 03/02/2023] [Indexed: 06/18/2023]
Abstract
Following the demonstration of laser-induced ultrafast demagnetization in ferromagnetic nickel, several theoretical and phenomenological propositions have sought to uncover its underlying physics. In this work we revisit the three temperature model (3TM) and the microscopic three temperature model (M3TM) to perform a comparative analysis of ultrafast demagnetization in 20 nm thick cobalt, nickel and permalloy thin films measured using an all-optical pump-probe technique. In addition to the ultrafast dynamics at the femtosecond timescales, the nanosecond magnetization precession and damping are recorded at various pump excitation fluences revealing a fluence-dependent enhancement in both the demagnetization times and the damping factors. We confirm that the Curie temperature to magnetic moment ratio of a given system acts as a figure of merit for the demagnetization time, while the demagnetization times and damping factors show an apparent sensitivity to the density of states at the Fermi level for a given system. Further, from numerical simulations of the ultrafast demagnetization based on both the 3TM and the M3TM, we extract the reservoir coupling parameters that best reproduce the experimental data and estimate the value of the spin flip scattering probability for each system. We discuss how the fluence-dependence of inter-reservoir coupling parameters so extracted may reflect a role played by nonthermal electrons in the magnetization dynamics at low laser fluences.
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Affiliation(s)
- Suchetana Mukhopadhyay
- Department of Condensed Matter and Materials Physics, S.N. Bose National Center for Basic Sciences, Block-JD, Sector III, Salt Lake, Kolkata, 700106, India
| | - Sudip Majumder
- Department of Condensed Matter and Materials Physics, S.N. Bose National Center for Basic Sciences, Block-JD, Sector III, Salt Lake, Kolkata, 700106, India
| | - Surya Narayan Panda
- Department of Condensed Matter and Materials Physics, S.N. Bose National Center for Basic Sciences, Block-JD, Sector III, Salt Lake, Kolkata, 700106, India
| | - Anjan Barman
- Department of Condensed Matter and Materials Physics, S.N. Bose National Center for Basic Sciences, Block-JD, Sector III, Salt Lake, Kolkata, 700106, India
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19
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Spin and Orbital Symmetry Breakings Central to the Laser-Induced Ultrafast Demagnetization of Transition Metals. Symmetry (Basel) 2023. [DOI: 10.3390/sym15020457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023] Open
Abstract
The role of spin and orbital rotational symmetry on the laser-induced magnetization dynamics of itinerant-electron ferromagnets was theoretically investigated. The ultrafast demagnetization of transition metals is shown to be the direct consequence of the fundamental breaking of these conservation laws in the electronic system, an effect that is inherent to the nature of spin-orbit and electron-lattice interactions. A comprehensive symmetry analysis is complemented by exact numerical calculations of the time evolution of optically excited ferromagnetic ground states in the framework of a many-body electronic Hamiltonian. Thus, quantitative relations are established between the strength of the interactions that break the rotational symmetries and the time scales that are relevant for the magnetization dynamics.
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20
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Wang S, Qin W, Zhang S, Lou Y, Liu C, Wu T, He Q, Tian C, Zhou L, Wu Y, Tao Z. Nanoengineered Spintronic-Metasurface Terahertz Emitters Enable Beam Steering and Full Polarization Control. NANO LETTERS 2022; 22:10111-10119. [PMID: 36512804 DOI: 10.1021/acs.nanolett.2c03906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The demand for emerging applications at the terahertz frequencies motivates the development of novel and multifunctional devices for the generation and manipulation of terahertz waves. In this work, we report the realization of multifunctional spintronic-metasurface emitters, which allow simultaneous beam-steering and full polarization control over a broadband terahertz beam. This is achieved through engineering individual meta-atoms with nanoscale magnetic heterostructures and, thus, implementing microscopical control over the laser-induced spin and charge dynamics. By arranging the spintronic meta-atoms in the metagrating geometry, the generated terahertz beam can be flexibly steered in space between different orders of diffraction. Furthermore, we demonstrate a simultaneous control over the terahertz polarization states at different emission angles and show that the two control capabilities are mutually independent of each other. The nanoengineered multifunctional terahertz emitter demonstrated in this work can provide a solution to the challenge associated with a growing variety of applications of terahertz technology.
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Affiliation(s)
- Shunjia Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai200433, China
| | - Wentao Qin
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Shanghai Research Center for Quantum Sciences, Fudan University, Shanghai200433, China
| | - Sheng Zhang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai200433, China
| | - Yuchen Lou
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai200433, China
| | - Changqin Liu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Shanghai Research Center for Quantum Sciences, Fudan University, Shanghai200433, China
| | - Tong Wu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Shanghai Research Center for Quantum Sciences, Fudan University, Shanghai200433, China
| | - Qiong He
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai200433, China
| | - Chuanshan Tian
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai200433, China
| | - Lei Zhou
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai200433, China
| | - Yizheng Wu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Shanghai Research Center for Quantum Sciences, Fudan University, Shanghai200433, China
| | - Zhensheng Tao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai200433, China
- Key Laboratory of Micro and Nano Photonic Structures (MOE), Fudan University, Shanghai200433, China
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21
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Li Z, Jiang Y, Jin Z, Li Z, Lu X, Ye Z, Pang JY, Xu Y, Peng Y. Terahertz Emission Spectroscopy of Ultrafast Coupled Spin and Charge Dynamics in Nanometer Ferromagnetic Heterostructures. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12234267. [PMID: 36500890 PMCID: PMC9741209 DOI: 10.3390/nano12234267] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 11/24/2022] [Accepted: 11/28/2022] [Indexed: 06/12/2023]
Abstract
Due to its high sensitivity and because it does not rely on the magneto-optical response, terahertz (THz) emission spectroscopy has been used as a powerful time-resolved tool for investigating ultrafast demagnetization and spin current dynamics in nanometer-thick ferromagnetic (FM)/heavy metal (HM) heterostructures. Here, by changing the order of the conductive HM coating on the FM nanometer film, the dominant electric dipole contribution to the laser-induced THz radiation can be unraveled from the ultrafast magnetic dipole. Furthermore, to take charge equilibration into account, we separate the femtosecond laser-induced spin-to-charge converted current and the instantaneous discharging current within the illuminated area. The THz emission spectroscopy gives us direct information into the coupled spin and charge dynamics during the first moments of the light-matter interaction. Our results also open up new perspectives to manipulate and optimize the ultrafast charge current for promising high-performance and broadband THz radiation.
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Affiliation(s)
- Zhangshun Li
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Yexin Jiang
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Zuanming Jin
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Zhuoyi Li
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
| | - Xianyang Lu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
| | - Zhijiang Ye
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Jin-Yi Pang
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
| | - Yongbing Xu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
| | - Yan Peng
- Terahertz Technology Innovation Research Institute, Terahertz Spectrum and Imaging Technology Cooperative Innovation Center, Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
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22
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Beens M, de Mare KA, Duine RA, Koopmans B. Spin-polarized hot electron transport versus spin pumping mediated by local heating. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 35:035803. [PMID: 36368045 DOI: 10.1088/1361-648x/aca24e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 11/11/2022] [Indexed: 06/16/2023]
Abstract
A 'toy model'-aimed at capturing the essential physics-is presented that jointly describes spin-polarized hot electron transport and spin pumping driven by local heating. These two processes both contribute to spin-current generation in laser-excited magnetic heterostructures. The model is used to compare the two contributions directly. The spin-polarized hot electron current is modeled as one generation of hot electrons with a spin-dependent excitation and relaxation scheme. Upon decay, the excess energy of the hot electrons is transferred to a thermalized electron bath. The elevated electron temperature leads to an increased rate of electron-magnon scattering processes and yields a local accumulation of spin. This process is dubbed as spin pumping by local heating. The built-up spin accumulation is effectively driven out of the ferromagnetic system by (interfacial) electron transport. Within our model, the injected spin current is dominated by the contribution resulting from spin pumping, while the hot electron spin current remains relatively small. We derive that this observation is related to the ratio between the Fermi temperature and Curie temperature, and we show what other fundamental parameters play a role.
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Affiliation(s)
- M Beens
- Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
| | - K A de Mare
- Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
| | - R A Duine
- Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
- Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands
| | - B Koopmans
- Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
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23
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Jiang T, Zhao X, Chen Z, You Y, Lai T, Zhao J. Ultrafast Dynamics of Demagnetization in FeMn/MnGa Bilayer Nanofilm Structures via Phonon Transport. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12224088. [PMID: 36432373 PMCID: PMC9698983 DOI: 10.3390/nano12224088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 11/17/2022] [Accepted: 11/18/2022] [Indexed: 06/04/2023]
Abstract
Superdiffusive spin transport has been proposed as a new mechanism of ultrafast demagnetization in layered magnetic nanostructures and demonstrated experimentally. However, it is unknown if it is possible for phonon transport to occur and manipulate ultrafast demagnetization. Here, we explore the ultrafast dynamics of demagnetization of an antiferromagnet/ferromagnet bilayer nanostructure, of a FeMn/MnGa bilayer film prepared by molecular beam epitaxy. Ultrafast dynamics of a two-step demagnetization were observed through the time-resolved magneto-optical Kerr effect. The first-step fast component of the two-step demagnetization occurred within ~200 fs, while the second-step slow component emerged in a few tens of picoseconds. For a single MnGa film, only the ultrafast dynamics of the first-step fast demagnetization were observed, revealing that the second-step slow demagnetization originates from interlayer phonon transport. A four-temperature model considering phonon transport was developed and used to effectively reproduce the observed ultrafast dynamics of two-step demagnetization. Our results reveal the effect of phonon transport on demagnetization for the first time and open up a new route to manipulate ultrafast demagnetization in layered magnetic structures.
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Affiliation(s)
- Tianran Jiang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xupeng Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
| | - Zhifeng Chen
- School of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006, China
| | - Yongyong You
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Tianshu Lai
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
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24
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Agarwal P, Huang L, Ter Lim S, Singh R. Electric-field control of nonlinear THz spintronic emitters. Nat Commun 2022; 13:4072. [PMID: 35835753 PMCID: PMC9283400 DOI: 10.1038/s41467-022-31789-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 07/04/2022] [Indexed: 11/30/2022] Open
Abstract
Energy-efficient spintronic technology holds tremendous potential for the design of next-generation processors to operate at terahertz frequencies. Femtosecond photoexcitation of spintronic materials generates sub-picosecond spin currents and emission of terahertz radiation with broad bandwidth. However, terahertz spintronic emitters lack an active material platform for electric-field control. Here, we demonstrate a nonlinear electric-field control of terahertz spin current-based emitters using a single crystal piezoelectric Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) that endows artificial magnetoelectric coupling onto a spintronic terahertz emitter and provides 270% modulation of the terahertz field at remnant magnetization. The nonlinear electric-field control of the spins occurs due to the strain-induced change in magnetic energy of the ferromagnet thin-film. Results also reveal a robust and repeatable switching of the phase of the terahertz spin current. Electric-field control of terahertz spintronic emitters with multiferroics and strain engineering offers opportunities for the on-chip realization of tunable energy-efficient spintronic-photonic integrated platforms. Spintronic terahertz (THz) emitters are a class of magnetic heterostructure where femtosecond laser excitations generate THz radiation emission. While they have great potential, electric field control of spintronic emitter remains a challenge. Here, by combining a spintronic emitter with a piezoelectric substrate, Agarwal et al. demonstrate electric field control of THz emission through induced piezostrain.
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Affiliation(s)
- Piyush Agarwal
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore.,Center for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore
| | - Lisen Huang
- Institute of Materials Research and Engineering A*STAR (Agency for Science, Technology and Research) 2 Fusionopolis Way, Innovis, Singapore, 138364, Singapore
| | - Sze Ter Lim
- Institute of Materials Research and Engineering A*STAR (Agency for Science, Technology and Research) 2 Fusionopolis Way, Innovis, Singapore, 138364, Singapore
| | - Ranjan Singh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Singapore. .,Center for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore.
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25
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Shelukhin LA, Gareev RR, Zbarsky V, Walowski J, Münzenberg M, Pertsev NA, Kalashnikova AM. Spin reorientation transition in CoFeB/MgO/CoFeB tunnel junction enabled by ultrafast laser-induced suppression of perpendicular magnetic anisotropy. NANOSCALE 2022; 14:8153-8162. [PMID: 35621055 DOI: 10.1039/d2nr00637e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Magnetic tunnel junction (MTJ) is a leading contender for next generation high-density nonvolatile memory technology. Fast and efficient switching of MTJs between different resistance states is a challenging problem, which can be tackled by using an unconventional stimulus-a femtosecond laser pulse. Herein, we report an experimental study of the laser-induced magnetization dynamics in a Co20Fe60B20/MgO/Co20Fe60B20 (CoFeB/MgO/CoFeB) MTJ with ultrathin CoFeB electrodes possessing perpendicular magnetic anisotropy (PMA). In addition to ultrafast demagnetization, a femtosecond laser pulse gives rise to a decaying magnetization precession in the thinner CoFeB layer subjected to an in-plane magnetic field, while the magnetization of the thicker CoFeB layer remains aligned with the applied field. Remarkably, the precession frequency demonstrates a strong and nonlinear rise with increasing pump fluence, which stems from the complete laser-induced suppression of PMA in the 1.2 nm-thick CoFeB electrode reached at a moderate fluence of about 1.8 mJ cm-2 at room temperature. This important feature signifies that the laser excitation of such an electrode can enable an ultrafast transition from a perpendicular-to-plane to an in-plane magnetization orientation in the absence of a magnetic field and reveals the feasibility of the laser-driven switching of MTJ between different states. The revealed gradual quenching of PMA with increasing fluence is explained by the laser-induced heating of the MTJ, which affects the interfacial magnetic anisotropy stronger than the shape anisotropy. Interestingly, at low fluences, the values of interfacial anisotropy and saturation magnetization altered by the laser excitation scale with each other as expected for the two-site anisotropic exchange interaction, but the scaling exponent increases significantly at moderate fluences, which enables the realization of a laser-induced spin reorientation transition.
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Affiliation(s)
| | - Rashid R Gareev
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Vladyslav Zbarsky
- University of Greifswald, Institute of Physics, Felix Hausdorff Str. 6, D-17489 Greifswald, Germany
| | - Jakob Walowski
- University of Greifswald, Institute of Physics, Felix Hausdorff Str. 6, D-17489 Greifswald, Germany
| | - Markus Münzenberg
- University of Greifswald, Institute of Physics, Felix Hausdorff Str. 6, D-17489 Greifswald, Germany
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26
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Yao K, Steinbach F, Borchert M, Schick D, Engel D, Bencivenga F, Mincigrucci R, Foglia L, Pedersoli E, De Angelis D, Pancaldi M, Wehinger B, Capotondi F, Masciovecchio C, Eisebitt S, von Korff Schmising C. All-Optical Switching on the Nanometer Scale Excited and Probed with Femtosecond Extreme Ultraviolet Pulses. NANO LETTERS 2022; 22:4452-4458. [PMID: 35605204 DOI: 10.1021/acs.nanolett.2c01060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ultrafast control of magnetization on the nanometer length scale, in particular all-optical switching, is key to putting ultrafast magnetism on the path toward future technological application in data storage technology. However, magnetization manipulation with light on this length scale is challenging due to the wavelength limitations of optical radiation. Here, we excite transient magnetic gratings in a GdFe alloy with a periodicity of 87 nm by the interference of two coherent femtosecond light pulses in the extreme ultraviolet spectral range. The subsequent ultrafast evolution of the magnetization pattern is probed by diffraction of a third, time-delayed pulse tuned to the Gd N-edge at a wavelength of 8.3 nm. By examining the simultaneously recorded first and second order diffractions and by performing reference real-space measurements with a wide-field magneto-optical microscope with femtosecond time resolution, we can conclusively demonstrate the ultrafast emergence of all-optical switching on the nanometer length scale.
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Affiliation(s)
- Kelvin Yao
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Felix Steinbach
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Martin Borchert
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Daniel Schick
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Dieter Engel
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Filippo Bencivenga
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Riccardo Mincigrucci
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Laura Foglia
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Emanuele Pedersoli
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Dario De Angelis
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Matteo Pancaldi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Björn Wehinger
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, via Torino 155, 30172 Venezia Mestre, Italy
| | - Flavio Capotondi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Claudio Masciovecchio
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14 km 163.5, 34149 Basovizza, Trieste, Italy
| | - Stefan Eisebitt
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
- Institut fuer Optik und Atomare Physik, Technische Universitaet Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
| | - Clemens von Korff Schmising
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
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27
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Liu W, Wang Z, Chen Z, Luo J, Li S, Wang L. Algorithm advances and applications of time‐dependent first‐principles simulations for ultrafast dynamics. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1577] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Wen‐Hao Liu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors Chinese Academy of Sciences Beijing China
- Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing China
| | - Zhi Wang
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors Chinese Academy of Sciences Beijing China
| | - Zhang‐Hui Chen
- Materials Science Division Lawrence Berkeley National Laboratory Berkeley California USA
| | - Jun‐Wei Luo
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors Chinese Academy of Sciences Beijing China
- Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing China
- Beijing Academy of Quantum Information Sciences Beijing China
| | - Shu‐Shen Li
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors Chinese Academy of Sciences Beijing China
- Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing China
- Beijing Academy of Quantum Information Sciences Beijing China
| | - Lin‐Wang Wang
- Materials Science Division Lawrence Berkeley National Laboratory Berkeley California USA
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28
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Li P, Liu S, Chen X, Geng C, Wu X. Spintronic terahertz emission with manipulated polarization (STEMP). FRONTIERS OF OPTOELECTRONICS 2022; 15:12. [PMID: 36637604 PMCID: PMC9756272 DOI: 10.1007/s12200-022-00011-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 01/11/2022] [Indexed: 06/17/2023]
Abstract
Highly efficient generation and arbitrary manipulation of spin-polarized terahertz (THz) radiation will enable chiral lightwave driven quantum nonequilibrium state regulation, induce new electronic structures, consequently provide a powerful experimental tool for investigation of nonlinear THz optics and extreme THz science and applications. THz circular dichromic spectroscopy, ultrafast electron bunch manipulation, as well as THz imaging, sensing, and telecommunication, also need chiral THz waves. Here we review optical generation of circularly-polarized THz radiation but focus on recently emerged polarization tunable spintronic THz emission techniques, which possess many advantages of ultra-broadband, high efficiency, low cost, easy for integration and so on. We believe that chiral THz sources based on the combination of electron spin, ultrafast optical techniques and material structure engineering will accelerate the development of THz science and applications.
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Affiliation(s)
- Peiyan Li
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Shaojie Liu
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Xinhou Chen
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Chunyan Geng
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Xiaojun Wu
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China.
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China.
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China.
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29
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De A, Arekapudi SSPK, Koch L, Samad F, Panda SN, Böhm B, Hellwig O, Barman A. Magnetic Configuration Driven Femtosecond Spin Dynamics in Synthetic Antiferromagnets. ACS APPLIED MATERIALS & INTERFACES 2022; 14:13970-13979. [PMID: 35275629 DOI: 10.1021/acsami.2c01555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Ultrafast demagnetization in diverse materials has sparked immense research activities due to its captivating richness and contested underlying mechanisms. Among these, the two most celebrated mechanisms have been the spin-flip scattering (SFS) and spin transport (ST) of optically excited carriers. In this work, we have investigated femtosecond laser-induced ultrafast demagnetization in perpendicular magnetic anisotropy-based synthetic antiferromagnets (p-SAFs) where [Co/Pt]n-1/Co multilayer blocks are separated by Ru or Ir spacers. Our investigation conclusively shows that the ST of optically excited carriers can have a significant contribution to the ultrafast demagnetization in addition to SFS processes. Moreover, we have also achieved an active control over the individual mechanisms by specially designing the SAF samples and altering the external magnetic field and excitation fluence. Our study provides a vital understanding of the underlying mechanism of ultrafast demagnetization in synthetic antiferromagnets, which will be crucial in future research and applications of antiferromagnetic spintronics.
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Affiliation(s)
- Anulekha De
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
| | | | - Leopold Koch
- Institute of Physics, Chemnitz University of Technology, Reichenhainer Straße 70, D-09107 Chemnitz, Germany
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Fabian Samad
- Institute of Physics, Chemnitz University of Technology, Reichenhainer Straße 70, D-09107 Chemnitz, Germany
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Surya Narayan Panda
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
| | - Benny Böhm
- Institute of Physics, Chemnitz University of Technology, Reichenhainer Straße 70, D-09107 Chemnitz, Germany
| | - Olav Hellwig
- Institute of Physics, Chemnitz University of Technology, Reichenhainer Straße 70, D-09107 Chemnitz, Germany
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Anjan Barman
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
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30
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Ultrafast time-evolution of chiral Néel magnetic domain walls probed by circular dichroism in x-ray resonant magnetic scattering. Nat Commun 2022; 13:1412. [PMID: 35301298 PMCID: PMC8931105 DOI: 10.1038/s41467-022-28899-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 02/18/2022] [Indexed: 11/29/2022] Open
Abstract
Non-collinear spin textures in ferromagnetic ultrathin films are attracting a renewed interest fueled by possible fine engineering of several magnetic interactions, notably the interfacial Dzyaloshinskii-Moriya interaction. This allows for the stabilization of complex chiral spin textures such as chiral magnetic domain walls (DWs), spin spirals, and magnetic skyrmions among others. We report here on the behavior of chiral DWs at ultrashort timescale after optical pumping in perpendicularly magnetized asymmetric multilayers. The magnetization dynamics is probed using time-resolved circular dichroism in x-ray resonant magnetic scattering (CD-XRMS). We observe a picosecond transient reduction of the CD-XRMS, which is attributed to the spin current-induced coherent and incoherent torques within the continuously varying spin texture of the DWs. We argue that a specific demagnetization of the inner structure of the DW induces a flow of spins from the interior of the neighboring magnetic domains. We identify this time-varying change of the DW texture shortly after the laser pulse as a distortion of the homochiral Néel shape toward a transient mixed Bloch-Néel-Bloch texture along a direction transverse to the DW. There is interest in encoding of information in complex spin structures present in magnetic systems, such as domain walls. Here, Léveillé et al study the ultrafast dynamics of chiral domain walls, and show the emergence of a transient spin chiral texture at the domain wall.
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31
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Chen X, Wang H, Liu H, Wang C, Wei G, Fang C, Wang H, Geng C, Liu S, Li P, Yu H, Zhao W, Miao J, Li Y, Wang L, Nie T, Zhao J, Wu X. Generation and Control of Terahertz Spin Currents in Topology-Induced 2D Ferromagnetic Fe 3 GeTe 2 |Bi 2 Te 3 Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2106172. [PMID: 34816497 DOI: 10.1002/adma.202106172] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 11/10/2021] [Indexed: 06/13/2023]
Abstract
Future information technologies for low-dissipation quantum computation, high-speed storage, and on-chip communication applications require the development of atomically thin, ultracompact, and ultrafast spintronic devices in which information is encoded, stored, and processed using electron spin. Exploring low-dimensional magnetic materials, designing novel heterostructures, and generating and controlling ultrafast electron spin in 2D magnetism at room temperature, preferably in the unprecedented terahertz (THz) regime, is in high demand. Using THz emission spectroscopy driven by femtosecond laser pulses, optical THz spin-current bursts at room temperature in the 2D van der Waals ferromagnetic Fe3 GeTe2 (FGT) integrated with Bi2 Te3 as a topological insulator are successfully realized. The symmetry of the THz radiation is effectively controlled by the optical pumping incidence and external magnetic field directions, indicating that the THz generation mechanism is the inverse Edelstein effect contributed spin-to-charge conversion. Thickness-, temperature-, and structure-dependent nontrivial THz transients reveal that topology-enhanced interlayer exchange coupling increases the FGT Curie temperature to room temperature, which provides an effective approach for engineering THz spin-current pulses. These results contribute to the goal of all-optical generation, manipulation, and detection of ultrafast THz spin currents in room-temperature 2D magnetism, accelerating the development of atomically thin high-speed spintronic devices.
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Affiliation(s)
- Xinhou Chen
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Hangtian Wang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Haijiang Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Chun Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Gaoshuai Wei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chan Fang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Hanchen Wang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Chunyan Geng
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Shaojie Liu
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
| | - Peiyan Li
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Haiming Yu
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
| | - Weisheng Zhao
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Jungang Miao
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
| | - Yutong Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
| | - Li Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Tianxiao Nie
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, 100191, China
- Hefei Innovation Research Institute, Beihang University, Hefei, 230013, China
| | - Jimin Zhao
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, 523808, China
| | - Xiaojun Wu
- School of Electronic and Information Engineering, Beihang University, Beijing, 100191, China
- School of Cyber Science and Technology, Beihang University, Beijing, 100191, China
- Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China
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32
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Tauchert SR, Volkov M, Ehberger D, Kazenwadel D, Evers M, Lange H, Donges A, Book A, Kreuzpaintner W, Nowak U, Baum P. Polarized phonons carry angular momentum in ultrafast demagnetization. Nature 2022; 602:73-77. [PMID: 35110761 DOI: 10.1038/s41586-021-04306-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 12/01/2021] [Indexed: 11/10/2022]
Abstract
Magnetic phenomena are ubiquitous in nature and indispensable for modern science and technology, but it is notoriously difficult to change the magnetic order of a material in a rapid way. However, if a thin nickel film is subjected to ultrashort laser pulses, it loses its magnetic order almost completely within femtosecond timescales1. This phenomenon is widespread2-7 and offers opportunities for rapid information processing8-11 or ultrafast spintronics at frequencies approaching those of light8,9,12. Consequently, the physics of ultrafast demagnetization is central to modern materials research1-7,13-28, but a crucial question has remained elusive: if a material loses its magnetization within mere femtoseconds, where is the missing angular momentum in such a short time? Here we use ultrafast electron diffraction to reveal in nickel an almost instantaneous, long-lasting, non-equilibrium population of anisotropic high-frequency phonons that appear within 150-750 fs. The anisotropy plane is perpendicular to the direction of the initial magnetization and the atomic oscillation amplitude is 2 pm. We explain these observations by means of circularly polarized phonons that quickly absorb the angular momentum of the spin system before macroscopic sample rotation. The time that is needed for demagnetization is related to the time it takes to accelerate the atoms. These results provide an atomistic picture of the Einstein-de Haas effect and signify the general importance of polarized phonons for non-equilibrium dynamics and phase transitions.
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Affiliation(s)
- S R Tauchert
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany.,Ludwig-Maximilians-Universität München, Garching, Germany
| | - M Volkov
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany.,Ludwig-Maximilians-Universität München, Garching, Germany
| | - D Ehberger
- Ludwig-Maximilians-Universität München, Garching, Germany
| | - D Kazenwadel
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - M Evers
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - H Lange
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - A Donges
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - A Book
- Technische Universität München, Physik-Department E21, Garching, Germany
| | - W Kreuzpaintner
- Technische Universität München, Physik-Department E21, Garching, Germany.,Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing, China.,Spallation Neutron Source Science Center, Dongguan, China
| | - U Nowak
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany
| | - P Baum
- Universität Konstanz, Fachbereich Physik, Konstanz, Germany. .,Ludwig-Maximilians-Universität München, Garching, Germany.
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33
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Abstract
Advances over the past decade have presented new avenues to achieve control over material properties using intense pulses of electromagnetic radiation, with frequencies ranging from optical (approximately 1 PHz, or 1015 Hz) down to below 1 THz (1012 Hz). Some of these new developments have arisen from new experimental methods to drive and observe transient material properties, while others have emerged from new computational techniques that have made nonequilibrium dynamics more tractable to our understanding. One common issue with most attempts to realize control using electromagnetic pulses is the dissipation of energy, which in many cases poses a limit due to uncontrolled heating and has led to strong interest in using lower frequency and/or highly specific excitations to minimize this effect. Emergent developments in experimental tools using shaped X-ray pulses may in the future offer new possibilities for material control, provided that the issue of heat dissipation can be resolved for higher frequency light. The concept of using appropriately shaped pulses of light to control the properties of materials has a range of potential applications, and relies on an understanding of intricate couplings within the material.![]()
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Affiliation(s)
- Steven L Johnson
- Institute for Quantum Electronics, ETH Zürich, Auguste-Piccard-Hof 1, 8093 Zürich, Switzerland.
- SwissFEL, Paul Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
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34
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Rana B, Mondal AK, Bandyopadhyay S, Barman A. Applications of nanomagnets as dynamical systems: I. NANOTECHNOLOGY 2021; 33:062007. [PMID: 34633310 DOI: 10.1088/1361-6528/ac2e75] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Abstract
When magnets are fashioned into nanoscale elements, they exhibit a wide variety of phenomena replete with rich physics and the lure of tantalizing applications. In this topical review, we discuss some of these phenomena, especially those that have come to light recently, and highlight their potential applications. We emphasize what drives a phenomenon, what undergirds the dynamics of the system that exhibits the phenomenon, how the dynamics can be manipulated, and what specific features can be harnessed for technological advances. For the sake of balance, we point out both advantages and shortcomings of nanomagnet based devices and systems predicated on the phenomena we discuss. Where possible, we chart out paths for future investigations that can shed new light on an intriguing phenomenon and/or facilitate both traditional and non-traditional applications.
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Affiliation(s)
- Bivas Rana
- Institute of Spintronics and Quantum Information, Faculty of Physics, Adam Mickiewicz University in Poznań, Uniwersytetu Poznanskiego 2, Poznań 61-614, Poland
- Center for Emergent Matter Science, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Amrit Kumar Mondal
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 106, India
| | - Supriyo Bandyopadhyay
- Department of Electrical and Computer Engineering, Virginia Commonwealth University, Richmond, VA, 23284, United States of America
| | - Anjan Barman
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 106, India
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35
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Shaw JM, Knut R, Armstrong A, Bhandary S, Kvashnin Y, Thonig D, Delczeg-Czirjak EK, Karis O, Silva TJ, Weschke E, Nembach HT, Eriksson O, Arena DA. Quantifying Spin-Mixed States in Ferromagnets. PHYSICAL REVIEW LETTERS 2021; 127:207201. [PMID: 34860034 DOI: 10.1103/physrevlett.127.207201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 09/08/2021] [Indexed: 06/13/2023]
Abstract
We quantify the presence of spin-mixed states in ferromagnetic 3D transition metals by precise measurement of the orbital moment. While central to phenomena such as Elliot-Yafet scattering, quantification of the spin-mixing parameter has hitherto been confined to theoretical calculations. We demonstrate that this information is also available by experimental means. Comparison of ferromagnetic resonance spectroscopy with x-ray magnetic circular dichroism results show that Kittel's original derivation of the spectroscopic g factor requires modification, to include spin mixing of valence band states. Our results are supported by ab initio relativistic electronic structure theory.
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Affiliation(s)
- Justin M Shaw
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
| | - Ronny Knut
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
| | - Abigail Armstrong
- Department of Physics, University of South Florida, Tampa, Florida 33620, USA
| | - Sumanta Bhandary
- School of Physics and CRANN Institute, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - Yaroslav Kvashnin
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
| | - Danny Thonig
- School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
| | | | - Olof Karis
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
| | - T J Silva
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
| | - Eugen Weschke
- Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen-Campus BESSY II, D-12489 Berlin, Germany
| | - Hans T Nembach
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, Colorado 80305, USA
- Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
| | - Olle Eriksson
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
- School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
| | - Dario A Arena
- Department of Physics, University of South Florida, Tampa, Florida 33620, USA
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36
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Da Browski M, Scott JN, Hendren WR, Forbes CM, Frisk A, Burn DM, Newman DG, Sait CRJ, Keatley PS, N'Diaye AT, Hesjedal T, van der Laan G, Bowman RM, Hicken RJ. Transition Metal Synthetic Ferrimagnets: Tunable Media for All-Optical Switching Driven by Nanoscale Spin Current. NANO LETTERS 2021; 21:9210-9216. [PMID: 34699234 DOI: 10.1021/acs.nanolett.1c03081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
All-optical switching of magnetization has great potential for use in future ultrafast and energy efficient nanoscale magnetic storage devices. So far, research has been almost exclusively focused on rare-earth based materials, which limits device tunability and scalability. Here, we show that a perpendicularly magnetized synthetic ferrimagnet composed of two distinct transition metal ferromagnetic layers, Ni3Pt and Co, can exhibit helicity independent magnetization switching. Switching occurs between two equivalent remanent states with antiparallel alignment of the Ni3Pt and Co magnetic moments and is observable over a broad temperature range. Time-resolved measurements indicate that the switching is driven by a spin-polarized current passing through the subnanometer Ir interlayer. The magnetic properties of this model system may be tuned continuously via subnanoscale changes in the constituent layer thicknesses as well as growth conditions, allowing the underlying mechanisms to be elucidated and paving the way to a new class of data storage devices.
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Affiliation(s)
- Maciej Da Browski
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - Jade N Scott
- School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
| | - William R Hendren
- School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
| | - Colin M Forbes
- School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
| | - Andreas Frisk
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - David M Burn
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - David G Newman
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - Connor R J Sait
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - Paul S Keatley
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - Alpha T N'Diaye
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Thorsten Hesjedal
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
| | - Gerrit van der Laan
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
| | - Robert M Bowman
- School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, United Kingdom
| | - Robert J Hicken
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
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37
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Zayko S, Kfir O, Heigl M, Lohmann M, Sivis M, Albrecht M, Ropers C. Ultrafast high-harmonic nanoscopy of magnetization dynamics. Nat Commun 2021; 12:6337. [PMID: 34732725 PMCID: PMC8566501 DOI: 10.1038/s41467-021-26594-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Accepted: 08/10/2021] [Indexed: 11/25/2022] Open
Abstract
Light-induced magnetization changes, such as all-optical switching, skyrmion nucleation, and intersite spin transfer, unfold on temporal and spatial scales down to femtoseconds and nanometers, respectively. Pump-probe spectroscopy and diffraction studies indicate that spatio-temporal dynamics may drastically affect the non-equilibrium magnetic evolution. Yet, direct real-space magnetic imaging on the relevant timescales has remained challenging. Here, we demonstrate ultrafast high-harmonic nanoscopy employing circularly polarized high-harmonic radiation for real-space imaging of femtosecond magnetization dynamics. We map quenched magnetic domains and localized spin structures in Co/Pd multilayers with a sub-wavelength spatial resolution down to 16 nm, and strobosocopically trace the local magnetization dynamics with 40 fs temporal resolution. Our compact experimental setup demonstrates the highest spatio-temporal resolution of magneto-optical imaging to date. Facilitating ultrafast imaging with high sensitivity to chiral and linear dichroism, we envisage a wide range of applications spanning magnetism, phase transitions, and carrier dynamics.
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Affiliation(s)
- Sergey Zayko
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany.
- Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany.
| | - Ofer Kfir
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
- Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
- School of Electrical Engineering, Tel Aviv University, 69978, Tel Aviv, Israel
| | - Michael Heigl
- Institute of Physics, University of Augsburg, 86159, Augsburg, Germany
| | - Michael Lohmann
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
| | - Murat Sivis
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
- Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Manfred Albrecht
- Institute of Physics, University of Augsburg, 86159, Augsburg, Germany
| | - Claus Ropers
- 4th Physical Institute-Solids and Nanostructures, University of Göttingen, 37077, Göttingen, Germany
- Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
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38
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Increasing the Efficiency of a Spintronic THz Emitter Based on WSe 2/FeCo. MATERIALS 2021; 14:ma14216479. [PMID: 34772004 PMCID: PMC8585334 DOI: 10.3390/ma14216479] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 10/21/2021] [Accepted: 10/22/2021] [Indexed: 11/17/2022]
Abstract
We report an increase in terahertz (THz) radiation efficiency due to FeCo/WSe2 structures in the reflection geometry. This can be attributed to an absorption increase in the alloy FeCo layer at the input FeCo/WSe2 interface due to constructive interference, as well as to the backward transport of hot carriers from FeCo to WSe2. In contrast to the transmission geometry, the THz generation efficiency in the reflection is much less dependent on the magnetic layer thickness. Our results suggest a cheap and efficient way to improve the characteristics of THz spintronic emitters with the conservation of a full set of their important properties.
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39
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Kumar S, Nivedan A, Singh A, Kumar Y, Malhotra P, Tondusson M, Freysz E, Kumar S. Optical damage limit of efficient spintronic THz emitters. iScience 2021; 24:103152. [PMID: 34646990 PMCID: PMC8496183 DOI: 10.1016/j.isci.2021.103152] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Revised: 08/25/2021] [Accepted: 09/16/2021] [Indexed: 11/04/2022] Open
Abstract
THz pulses are generated from femtosecond pulse-excited ferromagnetic/nonmagnetic spintronic heterostructures via inverse spin Hall effect. The highest possible THz signal strength from spintronic THz emitters is limited by the optical damage threshold of the corresponding heterostructures at the excitation wavelength. For the thickness-optimized spintronic heterostructure, the THz generation efficiency does not saturate with the excitation fluence even up till the damage threshold. Bilayer (Fe, CoFeB)/(Pt, Ta)-based ferromagnetic/nonmagnetic (FM/NM) spintronic heterostructures have been studied for an optimized performance for THz generation when pumped by sub-50 fs amplified laser pulses at 800 nm. Among them, CoFeB/Pt is the best combination for an efficient THz source. The optimized FM/NM spintronic heterostructure having α-phase Ta as the nonmagnetic layer shows the highest damage threshold as compared to those with Pt, irrespective of their generation efficiency. The damage threshold of the Fe/Ta heterostructure on a quartz substrate is ∼85 GW/cm2. THz generation efficiency of (CoFeB,Fe)/(Pt,Ta) spintronic film heterostructures Determination of optical damage threshold at NIR excitation Mean value of the optical damage threshold is ∼60 GW/cm2
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Affiliation(s)
- Sandeep Kumar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Anand Nivedan
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Arvind Singh
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Yogesh Kumar
- Laser Science and Technology Center, Metcalfe House, Civil Lines, New Delhi 110054, India
| | - Purnima Malhotra
- Laser Science and Technology Center, Metcalfe House, Civil Lines, New Delhi 110054, India
| | - Marc Tondusson
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, 33405 Talence, France
| | - Eric Freysz
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, 33405 Talence, France
| | - Sunil Kumar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
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40
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Zhuang S, Meisenheimer PB, Heron J, Hu JM. A Narrowband Spintronic Terahertz Emitter Based on Magnetoelastic Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2021; 13:48997-49006. [PMID: 34617721 DOI: 10.1021/acsami.1c13461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Narrowband terahertz (THz) radiation is crucial for high-resolution spectral identification, but a narrowband THz source driven by a femtosecond (fs) laser has remained scarce. Here, it is computationally predicted that a metal/dielectric/magnetoelastic heterostructure enables converting a fs laser pulse into a multicycle THz pulse with a narrow linewidth down to ∼1.5 GHz, which is in contrast to the single-cycle, broadband THz pulse from the existing fs-laser-excited emitters. It is shown that such narrowband THz pulse originates from the excitation and long-distance transport of THz spin waves in the magnetoelastic film, which can be enabled by a short strain pulse obtained from fs laser irradiation of the metal film when the thicknesses of the metal and magnetoelastic films both fall into a specific range. These results therefore reveal an approach to achieving optical generation of narrowband THz pulse based on heterostructure design, which also has implications in the design of THz magnonic devices.
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Affiliation(s)
- Shihao Zhuang
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
| | - Peter B Meisenheimer
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - John Heron
- Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Jia-Mian Hu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53705, United States
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41
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Abstract
In past decades, ultrafast spin dynamics in magnetic systems have been associated with heat deposition from high energy laser pulses, limiting the selective access to spin order. Here, we use a long wavelength terahertz (THz) pump–optical probe setup to measure structural features in the ultrafast time scale. We find that complete demagnetization is possible with <6 THz pulses. This occurs concurrently with longitudinal acoustic phonons and an electronic response.
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42
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Zhao HC, Xia H, Hu S, Lv YY, Zhao ZR, He J, Liang E, Ni G, Chen LY, Qiu XP, Zhou SM, Zhao HB. Large ultrafast-modulated Voigt effect in noncollinear antiferromagnet Mn 3Sn. Nat Commun 2021; 12:5266. [PMID: 34489461 PMCID: PMC8421456 DOI: 10.1038/s41467-021-25654-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 08/18/2021] [Indexed: 11/15/2022] Open
Abstract
The time-resolved magneto-optical (MO) Voigt effect can be utilized to study the Néel order dynamics in antiferromagnetic (AFM) materials, but it has been limited for collinear AFM spin configuration. Here, we have demonstrated that in Mn3Sn with an inverse triangular spin structure, the quench of AFM order by ultrafast laser pulses can result in a large Voigt effect modulation. The modulated Voigt angle is significantly larger than the polarization rotation due to the crystal-structure related linear dichroism effect and the modulated MO Kerr angle arising from the ferroic ordering of cluster magnetic octupole. The AFM order quench time shows negligible change with increasing temperature approaching the Néel temperature (TN), in markedly contrast with the pronounced slowing-down demagnetization typically observed in conventional magnetic materials. This atypical behavior can be explained by the influence of weakened Dzyaloshinskii–Moriya interaction rather than the smaller exchange splitting on the diminished AFM order near TN. The temperature-insensitive ultrafast spin manipulation can pave the way for high-speed spintronic devices either working at a wide range of temperature or demanding spin switching near TN. Mn3Sn is an anti-ferromagnetic material which displays a large magneto-optical Kerr effect, despite lacking a ferromagnetic moment. Here, the authors show that likewise, Mn3Sn, also presents a particularly large magneto-optical Voigt signal, with a negligible change in the quench time over a wide temperature range.
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Affiliation(s)
- H C Zhao
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China
| | - H Xia
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China.,Department of Physics, Fudan University, Shanghai, China
| | - S Hu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai, China
| | - Y Y Lv
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai, China
| | - Z R Zhao
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China
| | - J He
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China
| | - E Liang
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China
| | - G Ni
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China.
| | - L Y Chen
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China
| | - X P Qiu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai, China.
| | - S M Zhou
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai, China.
| | - H B Zhao
- Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), and Shanghai Ultra-precision Optical Manufacturing Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai, China. .,Shanghai Frontier Base of Intelligent Optoelectronics and Perception, Institute of Optoelectronics, Fudan University, Shanghai, China.
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43
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Panda SN, Majumder S, Choudhury S, Bhattacharya A, Sinha S, Barman A. Femtosecond laser-induced spin dynamics in single-layer graphene/CoFeB thin films. NANOSCALE 2021; 13:13709-13718. [PMID: 34477646 DOI: 10.1039/d1nr03397b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Graphene/ferromagnet hybrid heterostructures are important building blocks of spintronics due to the unique ability of graphene to transport spin current over unprecedented distances and possible increase in its spin-orbit coupling due to proximity and hybridization. Here, we present magnetization dynamics over a femtosecond to nanosecond timescale by employing an all-optical time-resolved magneto-optical Kerr effect technique in single-layer graphene (SLG)/CoFeB thin films with varying CoFeB thickness and compared them with reference CoFeB thin films without an SLG underlayer. Gilbert damping variation with CoFeB thickness is modelled to extract spin-mixing conductance for the SLG/CoFeB interface and isolate the two-magnon scattering contribution from spin pumping. In SLG/CoFeB, we have established an inverse relationship between ultrafast demagnetization time (τm) and the Gilbert damping parameter (α) induced by interfacial spin accumulation and pure spin-current transport via a spin pumping mechanism. This systematic study of ultrafast demagnetization in SLG/CoFeB heterostructures and its connection with magnetic damping can help to design graphene-based ultrahigh-speed spintronic devices.
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Affiliation(s)
- Surya Narayan Panda
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India.
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Lloyd-Hughes J, Oppeneer PM, Pereira Dos Santos T, Schleife A, Meng S, Sentef MA, Ruggenthaler M, Rubio A, Radu I, Murnane M, Shi X, Kapteyn H, Stadtmüller B, Dani KM, da Jornada FH, Prinz E, Aeschlimann M, Milot RL, Burdanova M, Boland J, Cocker T, Hegmann F. The 2021 ultrafast spectroscopic probes of condensed matter roadmap. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:353001. [PMID: 33951618 DOI: 10.1088/1361-648x/abfe21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 05/05/2021] [Indexed: 06/12/2023]
Abstract
In the 60 years since the invention of the laser, the scientific community has developed numerous fields of research based on these bright, coherent light sources, including the areas of imaging, spectroscopy, materials processing and communications. Ultrafast spectroscopy and imaging techniques are at the forefront of research into the light-matter interaction at the shortest times accessible to experiments, ranging from a few attoseconds to nanoseconds. Light pulses provide a crucial probe of the dynamical motion of charges, spins, and atoms on picosecond, femtosecond, and down to attosecond timescales, none of which are accessible even with the fastest electronic devices. Furthermore, strong light pulses can drive materials into unusual phases, with exotic properties. In this roadmap we describe the current state-of-the-art in experimental and theoretical studies of condensed matter using ultrafast probes. In each contribution, the authors also use their extensive knowledge to highlight challenges and predict future trends.
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Affiliation(s)
- J Lloyd-Hughes
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, PO Box 516, S-75120 Uppsala, Sweden
| | - T Pereira Dos Santos
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - A Schleife
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
- National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States of America
| | - S Meng
- Institute of Physics, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - M A Sentef
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - M Ruggenthaler
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
| | - A Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science (CFEL), 22761 Hamburg, Germany
- Nano-Bio Spectroscopy Group and ETSF, Universidad del País Vasco UPV/EHU 20018 San Sebastián, Spain
- Center for Computational Quantum Physics (CCQ), The Flatiron Institute, 162 Fifth Avenue, New York, NY, 10010, United States of America
| | - I Radu
- Department of Physics, Freie Universität Berlin, Germany
- Max Born Institute, Berlin, Germany
| | - M Murnane
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - X Shi
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - H Kapteyn
- JILA, University of Colorado and NIST, Boulder, CO, United States of America
| | - B Stadtmüller
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - K M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Japan
| | - F H da Jornada
- Department of Materials Science and Engineering, Stanford University, Stanford, 94305, CA, United States of America
| | - E Prinz
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - M Aeschlimann
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - R L Milot
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - M Burdanova
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom
| | - J Boland
- Photon Science Institute, Department of Electrical and Electronic Engineering, University of Manchester, United Kingdom
| | - T Cocker
- Michigan State University, United States of America
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Möller C, Probst H, Otto J, Stroh K, Mahn C, Steil S, Moshnyaga V, Jansen GSM, Steil D, Mathias S. Ultrafast element-resolved magneto-optics using a fiber-laser-driven extreme ultraviolet light source. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:065107. [PMID: 34243510 DOI: 10.1063/5.0050883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 05/16/2021] [Indexed: 06/13/2023]
Abstract
We present a novel setup to measure the transverse magneto-optical Kerr effect in the extreme ultraviolet spectral range based on a fiber laser amplifier system with a repetition rate between 100 and 300 kHz, which we use to measure element-resolved demagnetization dynamics. The setup is equipped with a strong electromagnet and a cryostat, allowing measurements between 10 and 420 K using magnetic fields up to 0.86 T. The performance of our setup is demonstrated by a set of temperature- and time-dependent magnetization measurements with elemental resolution.
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Affiliation(s)
- Christina Möller
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Henrike Probst
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Johannes Otto
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Karen Stroh
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Carsten Mahn
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Vasily Moshnyaga
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - G S Matthijs Jansen
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Daniel Steil
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
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46
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Park H, Jeong K, Maeng I, Sim KI, Pathak S, Kim J, Hong SB, Jung TS, Kang C, Kim JH, Hong J, Cho MH. Enhanced Spin-to-Charge Conversion Efficiency in Ultrathin Bi 2Se 3 Observed by Spintronic Terahertz Spectroscopy. ACS APPLIED MATERIALS & INTERFACES 2021; 13:23153-23160. [PMID: 33945256 DOI: 10.1021/acsami.1c03168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Owing to their remarkable spin-charge conversion (SCC) efficiency, topological insulators (TIs) are the most attractive candidates for spin-orbit torque generators. The simple method of enhancing SCC efficiency is to reduce the thickness of TI films to minimize the trivial bulk contribution. However, when the thickness reaches the ultrathin regime, the SCC efficiency decreases owing to intersurface hybridization. To overcome these contrary effects, we induced dehybridization of the ultrathin TI film by breaking the inversion symmetry between surfaces. For the TI film grown on an oxygen-deficient transition-metal oxide, the unbonded transition-metal d-orbitals affected only the bottom surface, resulting in asymmetric surface band structures. Spintronic terahertz emission spectroscopy, an emerging tool for investigating the SCC characteristics, revealed that the resulting SCC efficiency in symmetry-broken ultrathin Bi2Se3 was enhanced by up to ∼2.4 times.
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Affiliation(s)
- Hanbum Park
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Kwangsik Jeong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Division of Physics and Semiconductor Science, Dongguk University, Seoul 04620, Republic of Korea
| | - InHee Maeng
- YUHS-KRIBB, Medical Convergence Research Institute, College of Medicine, Yonsei University, Seoul 03722, Republic of Korea
| | - Kyung Ik Sim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS), Suwon 16419, Republic of Korea
| | - Sachin Pathak
- Department of Physics, School of Engineering, University of Petroleum and Energy Studies, Dehradun 248007, Uttarakhand, India
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Jonghoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Seok-Bo Hong
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Taek Sun Jung
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Chul Kang
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Jae Hoon Kim
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Jongill Hong
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Mann-Ho Cho
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
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47
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Chardonnet V, Hennes M, Jarrier R, Delaunay R, Jaouen N, Kuhlmann M, Ekanayake N, Léveillé C, von Korff Schmising C, Schick D, Yao K, Liu X, Chiuzbăian GS, Lüning J, Vodungbo B, Jal E. Toward ultrafast magnetic depth profiling using time-resolved x-ray resonant magnetic reflectivity. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2021; 8:034305. [PMID: 34235231 PMCID: PMC8225393 DOI: 10.1063/4.0000109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/01/2021] [Indexed: 06/13/2023]
Abstract
During the last two decades, a variety of models have been developed to explain the ultrafast quenching of magnetization following femtosecond optical excitation. These models can be classified into two broad categories, relying either on a local or a non-local transfer of angular momentum. The acquisition of the magnetic depth profiles with femtosecond resolution, using time-resolved x-ray resonant magnetic reflectivity, can distinguish local and non-local effects. Here, we demonstrate the feasibility of this technique in a pump-probe geometry using a custom-built reflectometer at the FLASH2 free-electron laser (FEL). Although FLASH2 is limited to the production of photons with a fundamental wavelength of 4 nm ( ≃ 310 eV ), we were able to probe close to the Fe L 3 edge ( 706.8 eV ) of a magnetic thin film employing the third harmonic of the FEL. Our approach allows us to extract structural and magnetic asymmetry signals revealing two dynamics on different time scales which underpin a non-homogeneous loss of magnetization and a significant dilation of 2 Å of the layer thickness followed by oscillations. Future analysis of the data will pave the way to a full quantitative description of the transient magnetic depth profile combining femtosecond with nanometer resolution, which will provide further insight into the microscopic mechanisms underlying ultrafast demagnetization.
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Affiliation(s)
- Valentin Chardonnet
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Marcel Hennes
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Romain Jarrier
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Renaud Delaunay
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Nicolas Jaouen
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | | | | | - Cyril Léveillé
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | | | - Daniel Schick
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
| | - Kelvin Yao
- Max Born Institut für Nichtlineare Optik und Kurzzeitspektroskopie, 12489 Berlin, Germany
| | - Xuan Liu
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, B.P. 48, 91192 Gif-sur-Yvette, France
| | - Gheorghe S. Chiuzbăian
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Jan Lüning
- Helmholtz-Zentrum Berlin für Materialien und Energie, 14109 Berlin, Germany
| | - Boris Vodungbo
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
| | - Emmanuelle Jal
- Sorbonne Université, CNRS, Laboratoire de Chimie Physique-Matière et Rayonnement, 75005 Paris, France
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48
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Niwa H, Yoshikawa N, Kawaguchi M, Hayashi M, Shimano R. Switchable generation of azimuthally- and radially-polarized terahertz beams from a spintronic terahertz emitter. OPTICS EXPRESS 2021; 29:13331-13343. [PMID: 33985069 DOI: 10.1364/oe.422484] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/07/2021] [Indexed: 06/12/2023]
Abstract
We propose and demonstrate a method of generating two fundamental terahertz cylindrical vector beams (THz-CVBs), namely the azimuthally- and radially-polarized THz pulses, from a spintronic THz emitter. We begin by presenting that the spintronic emitter generates the HE21 mode, a quadrupole like polarization distribution, when placed between two magnets with opposing polarity. By providing an appropriate mode conversion using a triangular Si prism, we show both from experiment and numerical calculation that we obtain azimuthal and radial THz vector beams. The proposed method facilitates the access of CVBs and paves the way toward sophisticated polarization control in the THz regime.
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49
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Ksenzov D, Maznev AA, Unikandanunni V, Bencivenga F, Capotondi F, Caretta A, Foglia L, Malvestuto M, Masciovecchio C, Mincigrucci R, Nelson KA, Pancaldi M, Pedersoli E, Randolph L, Rahmann H, Urazhdin S, Bonetti S, Gutt C. Nanoscale Transient Magnetization Gratings Created and Probed by Femtosecond Extreme Ultraviolet Pulses. NANO LETTERS 2021; 21:2905-2911. [PMID: 33724854 DOI: 10.1021/acs.nanolett.0c05083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We utilize coherent femtosecond extreme ultraviolet (EUV) pulses from a free electron laser (FEL) to generate transient periodic magnetization patterns with periods as short as 44 nm. Combining spatially periodic excitation with resonant probing at the M-edge of cobalt allows us to create and probe transient gratings of electronic and magnetic excitations in a CoGd alloy. In a demagnetized sample, we observe an electronic excitation with a rise time close to the FEL pulse duration and ∼0.5 ps decay time indicative of electron-phonon relaxation. When the sample is magnetized to saturation in an external field, we observe a magnetization grating, which appears on a subpicosecond time scale as the sample is demagnetized at the maxima of the EUV intensity and then decays on the time scale of tens of picoseconds via thermal diffusion. The described approach opens multiple avenues for studying dynamics of ultrafast magnetic phenomena on nanometer length scales.
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Affiliation(s)
- Dmitriy Ksenzov
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, 57072, Siegen, Germany
| | - Alexei A Maznev
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | | | - Filippo Bencivenga
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Flavio Capotondi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Antonio Caretta
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Laura Foglia
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Marco Malvestuto
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Claudio Masciovecchio
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Riccardo Mincigrucci
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Keith A Nelson
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Matteo Pancaldi
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
| | - Emanuele Pedersoli
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
| | - Lisa Randolph
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, 57072, Siegen, Germany
| | - Hendrik Rahmann
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, 57072, Siegen, Germany
| | - Sergei Urazhdin
- Department of Physics, Emory University, Atlanta, Georgia 30322, United States
| | - Stefano Bonetti
- Department of Physics, Stockholm University, 106 91 Stockholm, Sweden
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, 30172 Venice, Italy
| | - Christian Gutt
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, 57072, Siegen, Germany
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50
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Golias E, Kumberg I, Gelen I, Thakur S, Gördes J, Hosseinifar R, Guillet Q, Dewhurst JK, Sharma S, Schüßler-Langeheine C, Pontius N, Kuch W. Ultrafast Optically Induced Ferromagnetic State in an Elemental Antiferromagnet. PHYSICAL REVIEW LETTERS 2021; 126:107202. [PMID: 33784145 DOI: 10.1103/physrevlett.126.107202] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 01/15/2021] [Accepted: 01/25/2021] [Indexed: 06/12/2023]
Abstract
We present evidence for an ultrafast optically induced ferromagnetic alignment of antiferromagnetic Mn in Co/Mn multilayers. We observe the transient ferromagnetic signal at the arrival of the pump pulse at the Mn L_{3} resonance using x-ray magnetic circular dichroism in reflectivity. The timescale of the effect is comparable to the duration of the excitation and occurs before the magnetization in Co is quenched. Theoretical calculations point to the imbalanced population of Mn unoccupied states caused by the Co interface for the emergence of this transient ferromagnetic state.
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Affiliation(s)
- E Golias
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - I Kumberg
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - I Gelen
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - S Thakur
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - J Gördes
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - R Hosseinifar
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Q Guillet
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - J K Dewhurst
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle, Germany
| | - S Sharma
- Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - C Schüßler-Langeheine
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein Straße 15, 12489 Berlin, Germany
| | - N Pontius
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein Straße 15, 12489 Berlin, Germany
| | - W Kuch
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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