1
|
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.
Collapse
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
| |
Collapse
|
2
|
Dutta S, Husain S, Kumar P, Gupta NK, Chaudhary S, Svedlindh P, Barman A. Manipulating ultrafast magnetization dynamics of ferromagnets using the odd-even layer dependence of two-dimensional transition metal di-chalcogenides. NANOSCALE 2024; 16:4105-4113. [PMID: 38349614 DOI: 10.1039/d3nr06197c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Two-dimensional transition metal dichalcogenides (TMDs) have drawn immense interest due to their strong spin-orbit coupling and unique layer number dependence in response to spin-valley coupling. This leads to the possibility of controlling the spin degree of freedom of the ferromagnet (FM) in thin film heterostructures and may prove to be of interest for next-generation spin-based devices. Here, we experimentally demonstrate the odd-even layer dependence of WS2 nanolayers by measurements of the ultrafast magnetization dynamics in WS2/Co3FeB thin film heterostructures by using time-resolved Kerr magnetometry. The fluence (photon energy per unit area) dependent magnetic damping (α) reveals the existence of broken symmetry and the dominance of inter- and intraband scattering for odd and even layers of WS2, respectively. The higher demagnetization time, τm, in 3 and 5 layers of WS2 is indicative of the interaction between spin-orbit and spin-valley coupling due to the broken symmetry. The lower τm in even layers as compared to the bare FM layer suggests the presence of a spin transport. By correlating τm and α, we pinpointed the dominant mechanisms of ultrafast demagnetization. The mechanism changes from spin transport to spin-flip scattering for even layers of WS2 with increasing fluence. A fundamental understanding of the two-dimensional material and its odd-even layer dependence at ultrashort timescales provides valuable information for designing next-generation spin-based devices.
Collapse
Affiliation(s)
- Soma Dutta
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India.
| | - Sajid Husain
- Department of Materials Science and Engineering, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden.
| | - Prabhat Kumar
- Department of Thin Films and Nanostructures, Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10/112, 162 00 Prague, Czech Republic
| | - Nanhe Kumar Gupta
- Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Sujeet Chaudhary
- Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Peter Svedlindh
- Department of Materials Science and Engineering, Uppsala University, Box 35, SE-751 03 Uppsala, Sweden.
| | - Anjan Barman
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India.
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Anh LD, Kobayashi M, Takeda T, Araki K, Okano R, Sumi T, Horio M, Yamamoto K, Kubota Y, Owada S, Yabashi M, Matsuda I, Tanaka M. Ultrafast Subpicosecond Magnetization of a 2D Ferromagnet. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2301347. [PMID: 37309900 DOI: 10.1002/adma.202301347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 05/12/2023] [Indexed: 06/14/2023]
Abstract
Strong spin-charge interactions in several ferromagnets are expected to lead to subpicosecond (sub-ps) magnetization of the magnetic materials through control of the carrier characteristics via electrical means, which is essential for ultrafast spin-based electronic devices. Thus far, ultrafast control of magnetization has been realized by optically pumping a large number of carriers into the d or f orbitals of a ferromagnet; however, it is extremely challenging to implement by electrical gating. This work demonstrates a new method for sub-ps magnetization manipulation called wavefunction engineering, in which only the spatial distribution (wavefunction) of s (or p) electrons is controlled and no change is required in the total carrier density. Using a ferromagnetic semiconductor (FMS) (In,Fe)As quantum well (QW), instant enhancement, as fast as 600 fs, of the magnetization is observed upon irradiating a femtosecond (fs) laser pulse. Theoretical analysis shows that the instant enhancement of the magnetization is induced when the 2D electron wavefunctions (WFs) in the FMS QW are rapidly moved by a photo-Dember electric field formed by an asymmetric distribution of the photocarriers. Because this WF engineering method can be equivalently implemented by applying a gate electric field, these results open a new way to realize ultrafast magnetic storage and spin-based information processing in present electronic systems.
Collapse
Affiliation(s)
- Le Duc Anh
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Saitama, Kawaguchi, 332-0012, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Masaki Kobayashi
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Takahito Takeda
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Kohsei Araki
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Ryo Okano
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Toshihide Sumi
- Institute of Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8581, Japan
| | - Masafumi Horio
- Institute of Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8581, Japan
| | - Kohei Yamamoto
- Institute for Molecular Science, Okazaki, Aichi, 444-8585, Japan
| | - Yuya Kubota
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
| | - Shigeki Owada
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo, 679-5198, Japan
| | - Makina Yabashi
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo, 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo, 679-5198, Japan
| | - Iwao Matsuda
- Institute of Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba, 277-8581, Japan
| | - Masaaki Tanaka
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Institute for Nano Quantum Information Electronics (NanoQuine), The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-0041, Japan
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
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.
Collapse
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
| |
Collapse
|
7
|
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.
Collapse
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
| |
Collapse
|
8
|
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.
Collapse
|
9
|
Unikandanunni V, Medapalli R, Asa M, Albisetti E, Petti D, Bertacco R, Fullerton EE, Bonetti S. Inertial Spin Dynamics in Epitaxial Cobalt Films. PHYSICAL REVIEW LETTERS 2022; 129:237201. [PMID: 36563189 DOI: 10.1103/physrevlett.129.237201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Accepted: 11/09/2022] [Indexed: 06/17/2023]
Abstract
We investigate the spin dynamics driven by terahertz magnetic fields in epitaxial thin films of cobalt in its three crystalline phases. The terahertz magnetic field generates a torque on the magnetization which causes it to precess for about 1 ps, with a subpicosecond temporal lag from the driving force. Then, the magnetization undergoes natural damped THz oscillations at a frequency characteristic of the crystalline phase. We describe the experimental observations solving the inertial Landau-Lifshitz-Gilbert equation. Using the results from the relativistic theory of magnetic inertia, we find that the angular momentum relaxation time η is the only material parameter needed to describe all the experimental evidence. Our experiments suggest a proportionality between η and the strength of the magnetocrystalline anisotropy.
Collapse
Affiliation(s)
| | - Rajasekhar Medapalli
- Center for Memory and Recording Research, University of California San Diego, San Diego, California 92093, USA
- Department of Physics, Lancaster University, Bailrigg, Lancaster LA1 4YW, United Kingdom
| | - Marco Asa
- Department of Physics, Politecnico di Milano Technical University, 20133 Milano, Italy
| | - Edoardo Albisetti
- Department of Physics, Politecnico di Milano Technical University, 20133 Milano, Italy
| | - Daniela Petti
- Department of Physics, Politecnico di Milano Technical University, 20133 Milano, Italy
| | - Riccardo Bertacco
- Department of Physics, Politecnico di Milano Technical University, 20133 Milano, Italy
| | - Eric E Fullerton
- Center for Memory and Recording Research, University of California San Diego, San Diego, California 92093, USA
| | - Stefano Bonetti
- Department of Physics, Stockholm University, 10691 Stockholm, Sweden
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, 30172 Venice, Italy
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|
11
|
Li S, Zhou L, Frauenheim T, He J. Light-Controlled Ultrafast Magnetic State Transition in Antiferromagnetic-Ferromagnetic van der Waals Heterostructures. J Phys Chem Lett 2022; 13:6223-6229. [PMID: 35770897 DOI: 10.1021/acs.jpclett.2c01476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Manipulating spin in antiferromagnetic (AFM) materials has great potential in AFM opto-spintronics. Laser pulses can induce a transient ferromagnetic (FM) state in AFM metallic systems but have never been proven in two-dimensional (2D) AFM semiconductors and related van der Waals (vdW) heterostructures. Herein, using 2D vdW heterostructures of FM MnS2 and AFM MXenes as prototypes, we investigated optically induced interlayer spin transfer dynamics based on real-time time-dependent density functional theory. We observed that laser pulses induce significant spin injection and interfacial atom-mediated spin transfer from MnS2 to Cr2CCl2. In particular, we first demonstrated the transient FM state in semiconducting AFM-FM heterostructures during photoexcited processes. The proximity magnetism breaks the magnetic symmetry of Cr2CCl2 in heterostructures. Our results provide a microscopic understanding of optically controlled interlayer spin dynamics in 2D magnetic heterostructures and open a new way to manipulate magnetic order in 2D materials for ultrafast opto-spintronics.
Collapse
Affiliation(s)
- Shuo Li
- Institute for Advanced Study, Chengdu University, Chengdu 610100, P. R. China
- Beijing Computational Science Research Center, Beijing 100193, P. R. China
| | - Liujiang Zhou
- School of Physics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China
| | - Thomas Frauenheim
- Beijing Computational Science Research Center, Beijing 100193, P. R. China
- Bremen Center for Computational Materials Science, University of Bremen, Bremen 28359, Germany
- Shenzhen JL Computational Science and Applied Research Institute, Shenzhen 518110, P. R. China
| | - Junjie He
- Bremen Center for Computational Materials Science, University of Bremen, Bremen 28359, Germany
- Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University in Prague, Prague 12843, Czechia
| |
Collapse
|
12
|
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
| |
Collapse
|
13
|
Windsor YW, Lee SE, Zahn D, Borisov V, Thonig D, Kliemt K, Ernst A, Schüßler-Langeheine C, Pontius N, Staub U, Krellner C, Vyalikh DV, Eriksson O, Rettig L. Exchange scaling of ultrafast angular momentum transfer in 4f antiferromagnets. NATURE MATERIALS 2022; 21:514-517. [PMID: 35210586 PMCID: PMC9064787 DOI: 10.1038/s41563-022-01206-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 01/18/2022] [Indexed: 06/14/2023]
Abstract
Ultrafast manipulation of magnetism bears great potential for future information technologies. While demagnetization in ferromagnets is governed by the dissipation of angular momentum1-3, materials with multiple spin sublattices, for example antiferromagnets, can allow direct angular momentum transfer between opposing spins, promising faster functionality. In lanthanides, 4f magnetic exchange is mediated indirectly through the conduction electrons4 (the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction), and the effect of such conditions on direct spin transfer processes is largely unexplored. Here, we investigate ultrafast magnetization dynamics in 4f antiferromagnets and systematically vary the 4f occupation, thereby altering the magnitude of the RKKY coupling energy. By combining time-resolved soft X-ray diffraction with ab initio calculations, we find that the rate of direct transfer between opposing moments is directly determined by this coupling. Given the high sensitivity of RKKY to the conduction electrons, our results offer a useful approach for fine tuning the speed of magnetic devices.
Collapse
Affiliation(s)
- Y W Windsor
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Berlin, Germany.
| | - S-E Lee
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Berlin, Germany
| | - D Zahn
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Berlin, Germany
| | - V Borisov
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
| | - D Thonig
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
- School of Science and Technology, Örebro University, Örebro, Sweden
| | - K Kliemt
- Physikalisches Institut, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - A Ernst
- Institute for Theoretical Physics, Johannes Kepler University, Linz, Austria
- Max-Planck-Institut für Mikrostrukturphysik, Halle (Saale), Germany
| | | | - N Pontius
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - U Staub
- Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland
| | - C Krellner
- Physikalisches Institut, Goethe-Universität Frankfurt, Frankfurt am Main, Germany
| | - D V Vyalikh
- Donostia International Physics Center (DIPC), Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
| | - O Eriksson
- Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
- School of Science and Technology, Örebro University, Örebro, Sweden
| | - L Rettig
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Berlin, Germany.
| |
Collapse
|
14
|
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.
Collapse
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
| |
Collapse
|
15
|
|
16
|
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.
Collapse
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.
| |
Collapse
|
17
|
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.
Collapse
|
18
|
Coherent control of asymmetric spintronic terahertz emission from two-dimensional hybrid metal halides. Nat Commun 2021; 12:5744. [PMID: 34593814 PMCID: PMC8484356 DOI: 10.1038/s41467-021-26011-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 09/14/2021] [Indexed: 11/24/2022] Open
Abstract
Next-generation terahertz (THz) sources demand lightweight, low-cost, defect-tolerant, and robust components with synergistic, tunable capabilities. However, a paucity of materials systems simultaneously possessing these desirable attributes and functionalities has made device realization difficult. Here we report the observation of asymmetric spintronic-THz radiation in Two-Dimensional Hybrid Metal Halides (2D-HMH) interfaced with a ferromagnetic metal, produced by ultrafast spin current under femtosecond laser excitation. The generated THz radiation exhibits an asymmetric intensity toward forward and backward emission direction whose directionality can be mutually controlled by the direction of applied magnetic field and linear polarization of the laser pulse. Our work demonstrates the capability for the coherent control of THz emission from 2D-HMHs, enabling their promising applications on the ultrafast timescale as solution-processed material candidates for future THz emitters. Terahertz radiation has wide array of potential uses, however, finding robust and tunable sources of terahertz radiation has been challenging. Here, Cong et al demonstrate a room temperature terahertz source composed of a two-dimensional hybrid metal halide and ferromagnetic heterostructure.
Collapse
|
19
|
Liu X, Merhe A, Jal E, Delaunay R, Jarrier R, Chardonnet V, Hennes M, Chiuzbaian SG, Légaré K, Hennecke M, Radu I, Von Korff Schmising C, Grunewald S, Kuhlmann M, Lüning J, Vodungbo B. Sub-15-fs X-ray pump and X-ray probe experiment for the study of ultrafast magnetization dynamics in ferromagnetic alloys. OPTICS EXPRESS 2021; 29:32388-32403. [PMID: 34615311 DOI: 10.1364/oe.430828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 08/30/2021] [Indexed: 06/13/2023]
Abstract
In this paper, we present a new setup for the measurement of element-specific ultrafast magnetization dynamics in ferromagnetic thin films with a sub-15-fs time resolution. Our experiment relies on a split and delay approach which allows us to fully exploit the shortest X-rays pulses delivered by X-ray Free Electrons Lasers (close to the attosecond range), in an X-ray pump - X-ray probe geometry. The setup performance is demonstrated by measuring the ultrafast elemental response of Ni and Fe during demagnetization of ferromagnetic Ni and Ni80Fe20 (Permalloy) samples upon resonant excitation at the corresponding absorption edges. The transient demagnetization process is measured in both reflection and transmission geometry using, respectively, the transverse magneto-optical Kerr effect (T-MOKE) and the Faraday effect as probing mechanisms.
Collapse
|
20
|
Subpicosecond metamagnetic phase transition in FeRh driven by non-equilibrium electron dynamics. Nat Commun 2021; 12:5088. [PMID: 34429414 PMCID: PMC8384879 DOI: 10.1038/s41467-021-25347-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 07/22/2021] [Indexed: 11/11/2022] Open
Abstract
Femtosecond light-induced phase transitions between different macroscopic orders provide the possibility to tune the functional properties of condensed matter on ultrafast timescales. In first-order phase transitions, transient non-equilibrium phases and inherent phase coexistence often preclude non-ambiguous detection of transition precursors and their temporal onset. Here, we present a study combining time-resolved photoelectron spectroscopy and ab-initio electron dynamics calculations elucidating the transient subpicosecond processes governing the photoinduced generation of ferromagnetic order in antiferromagnetic FeRh. The transient photoemission spectra are accounted for by assuming that not only the occupation of electronic states is modified during the photoexcitation process. Instead, the photo-generated non-thermal distribution of electrons modifies the electronic band structure. The ferromagnetic phase of FeRh, characterized by a minority band near the Fermi energy, is established 350 ± 30 fs after the laser excitation. Ab-initio calculations indicate that the phase transition is initiated by a photoinduced Rh-to-Fe charge transfer. In FeRh, it is possible to optically drive a phase transition between ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering. Here, using a combination of photoelectron spectroscopy and ab-initio calculations, the authors demonstrate the existence of a transient intermediate phase, explaining the delayed appearance of the FM phase.
Collapse
|
21
|
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.
Collapse
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
| |
Collapse
|
22
|
Eschenlohr A. Spin dynamics at interfaces on femtosecond timescales. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:013001. [PMID: 33034305 DOI: 10.1088/1361-648x/abb519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The excitation of magnetically ordered materials with ultrashort laser pulses results in magnetization dynamics on femto- to picosecond timescales. These non-equilibrium spin dynamics have emerged as a rapidly developing research field in recent years. Unraveling the fundamental microscopic processes in the interaction of ultrashort optical pulses with the charge, spin, orbital, and lattice degrees of freedom in magnetic materials shows the potential for controlling spin dynamics on their intrinsic timescales and thereby bring spintronics applications into the femtosecond range. In particular, femtosecond spin currents offer fascinating new possibilities to manipulate magnetization in an ultrafast and non-local manner, via spin injection and spin transfer torque at the interfaces of ferromagnetic layered structures. This topical review covers recent progress on spin dynamics at interfaces on femtosecond time scales. The development of the field of ultrafast spin dynamics in ferromagnetic heterostructures will be reviewed, starting from spin currents propagating on nanometer length scales through layered structures before focusing on femtosecond spin transfer at interfaces. The properties of these ultrafast spin-dependent charge currents will be discussed, as well as the materials dependence of femtosecond spin injection, the role of the interface properties, and competing microscopic processes leading to a loss of spin polarization on sub-picosecond timescales.
Collapse
Affiliation(s)
- A Eschenlohr
- Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany
| |
Collapse
|
23
|
Barlow K, Johansson JO. Ultrafast photoinduced dynamics in Prussian blue analogues. Phys Chem Chem Phys 2021; 23:8118-8131. [DOI: 10.1039/d1cp00535a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A review on ultrafast photoinduced processes in molecule-based magnets with an emphasis on Prussian blue analogues.
Collapse
Affiliation(s)
- Kyle Barlow
- EaStCHEM School of Chemistry
- University of Edinburgh
- David Brewster Road
- Edinburgh
- UK
| | - J. Olof Johansson
- EaStCHEM School of Chemistry
- University of Edinburgh
- David Brewster Road
- Edinburgh
- UK
| |
Collapse
|
24
|
Wang C, Liu Y. Ultrafast optical manipulation of magnetic order in ferromagnetic materials. NANO CONVERGENCE 2020; 7:35. [PMID: 33170368 PMCID: PMC7655883 DOI: 10.1186/s40580-020-00246-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 10/28/2020] [Indexed: 05/08/2023]
Abstract
The interaction between ultrafast lasers and magnetic materials is an appealing topic. It not only involves interesting fundamental questions that remain inconclusive and hence need further investigation, but also has the potential to revolutionize data storage technologies because such an opto-magnetic interaction provides an ultrafast and energy-efficient means to control magnetization. Fruitful progress has been made in this area over the past quarter century. In this paper, we review the state-of-the-art experimental and theoretical studies on magnetization dynamics and switching in ferromagnetic materials that are induced by ultrafast lasers. We start by describing the physical mechanisms of ultrafast demagnetization based on different experimental observations and theoretical methods. Both the spin-flip scattering theory and the superdiffusive spin transport model will be discussed in detail. Then, we will discuss laser-induced torques and resultant magnetization dynamics in ferromagnetic materials. Recent developments of all-optical switching (AOS) of ferromagnetic materials towards ultrafast magnetic storage and memory will also be reviewed, followed by the perspectives on the challenges and future directions in this emerging area.
Collapse
Affiliation(s)
- Chuangtang Wang
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA, 02115, USA
| | - Yongmin Liu
- Department of Electrical and Computer Engineering, Northeastern University, Boston, MA, 02115, USA.
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, 02115, USA.
| |
Collapse
|
25
|
Mertens F, Terschanski M, Mönkebüscher D, Ponzoni S, Bossini D, Cinchetti M. Wide spectral range ultrafast pump-probe magneto-optical spectrometer at low temperature, high-magnetic and electric fields. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:113001. [PMID: 33261465 DOI: 10.1063/5.0024449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 10/17/2020] [Indexed: 06/12/2023]
Abstract
We developed a table-top setup to perform magneto-optical pump-probe measurements with the possibility to independently tune the photon-energy of both pump and probe beams in the 0.5 eV-3.5 eV range. Our apparatus relies on a commercial turn-key amplified laser system, able to generate light pulses with duration shorter than or comparable to 100 fs throughout the whole spectral range. The repetition rate of the source can be modified via the computer in the 1 kHz to 1 MHz range. A commercial balanced detector is connected to a high-frequency digitizer, allowing for a highly-sensitive detection scheme: rotations of the probe polarization as small as 70 μdeg can be measured. Additionally, a DC magnetic field as high as 9 T and voltages in the kV regime can be applied on the sample. A cryostat allows us to precisely set the temperature of the specimen in the 4 K-420 K interval. We prove the performance of our setup by measuring the ultrafast demagnetization of a cobalt crystal as a function of a wide variety of experimental parameters.
Collapse
Affiliation(s)
- F Mertens
- Experimentelle Physik VI, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany
| | - M Terschanski
- Experimentelle Physik VI, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany
| | - D Mönkebüscher
- Experimentelle Physik VI, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany
| | - S Ponzoni
- Experimentelle Physik VI, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany
| | - D Bossini
- Experimentelle Physik VI, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany
| | - M Cinchetti
- Experimentelle Physik VI, TU Dortmund, Otto-Hahn-Straße 4, 44227 Dortmund, Germany
| |
Collapse
|
26
|
Zhang DL, Zhu J, Qu T, Lattery DM, Victora RH, Wang X, Wang JP. High-frequency magnetoacoustic resonance through strain-spin coupling in perpendicular magnetic multilayers. SCIENCE ADVANCES 2020; 6:6/38/eabb4607. [PMID: 32948586 PMCID: PMC7500926 DOI: 10.1126/sciadv.abb4607] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 07/29/2020] [Indexed: 05/29/2023]
Abstract
It is desirable to experimentally demonstrate an extremely high resonant frequency, assisted by strain-spin coupling, in technologically important perpendicular magnetic materials for device applications. Here, we directly observe the coupling of magnons and phonons in both time and frequency domains upon femtosecond laser excitation. This strain-spin coupling leads to a magnetoacoustic resonance in perpendicular magnetic [Co/Pd] n multilayers, reaching frequencies in the extremely high frequency (EHF) band, e.g., 60 GHz. We propose a theoretical model to explain the physical mechanism underlying the strain-spin interaction. Our model explains the amplitude increase of the magnetoacoustic resonance state with time and quantitatively predicts the composition of the combined strain-spin state near the resonance. We also detail its precise dependence on the magnetostriction. The results of this work offer a potential pathway to manipulating both the magnitude and timing of EHF and strongly coupled magnon-phonon excitations.
Collapse
Affiliation(s)
- De-Lin Zhang
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jie Zhu
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Tao Qu
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Dustin M Lattery
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - R H Victora
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Xiaojia Wang
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jian-Ping Wang
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| |
Collapse
|
27
|
Shim JH, Syed AA, Kim JI, Piao HG, Lee SH, Park SY, Choi YS, Lee KM, Kim HJ, Jeong JR, Hong JI, Kim DE, Kim DH. Role of non-thermal electrons in ultrafast spin dynamics of ferromagnetic multilayer. Sci Rep 2020; 10:6355. [PMID: 32286462 PMCID: PMC7156415 DOI: 10.1038/s41598-020-63452-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 02/27/2020] [Indexed: 11/09/2022] Open
Abstract
Understanding of ultrafast spin dynamics is crucial for future spintronic applications. In particular, the role of non-thermal electrons needs further investigation in order to gain a fundamental understanding of photoinduced demagnetization and remagnetization on a femtosecond time scale. We experimentally demonstrate that non-thermal electrons existing in the very early phase of the photoinduced demagnetization process play a key role in governing the overall ultrafast spin dynamics behavior. We simultaneously measured the time-resolved reflectivity (TR-R) and the magneto-optical Kerr effect (TR-MOKE) for a Co/Pt multilayer film. By using an extended three-temperature model (E3TM), the quantitative analysis, including non-thermal electron energy transfer into the subsystem (thermal electron, lattice, and spin), reveals that energy flow from non-thermal electrons plays a decisive role in determining the type I and II photoinduced spin dynamics behavior. Our finding proposes a new mechanism for understanding ultrafast remagnetization dynamics.
Collapse
Affiliation(s)
- Je-Ho Shim
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 37673, South Korea.,Max Planck POSTECH/KOREA Research Initiative, Pohang, 37673, South Korea
| | - Akbar Ali Syed
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 37673, South Korea.,Max Planck POSTECH/KOREA Research Initiative, Pohang, 37673, South Korea
| | - Jea-Il Kim
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 37673, South Korea.,Max Planck POSTECH/KOREA Research Initiative, Pohang, 37673, South Korea
| | - Hong-Guang Piao
- Department of Physics, Chungbuk National University, Cheongju, 28644, South Korea.,College of Science, China Three Gorges University, Yichang, 443002, P. R. China
| | - Sang-Hyuk Lee
- Department of Physics, Chungbuk National University, Cheongju, 28644, South Korea.,Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea
| | - Seung-Young Park
- Spin Engineering Physics Team, Korea Basic Science Institute, Daejeon, 34133, South Korea
| | - Yeon Suk Choi
- Spin Engineering Physics Team, Korea Basic Science Institute, Daejeon, 34133, South Korea
| | - Kyung Min Lee
- Department of Material Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 34134, South Korea
| | - Hyun-Joong Kim
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology, Daegu, 42988, South Korea
| | - Jong-Ryul Jeong
- Department of Material Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 34134, South Korea
| | - Jung-Il Hong
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology, Daegu, 42988, South Korea
| | - Dong Eon Kim
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 37673, South Korea. .,Max Planck POSTECH/KOREA Research Initiative, Pohang, 37673, South Korea.
| | - Dong-Hyun Kim
- Department of Physics, Chungbuk National University, Cheongju, 28644, South Korea.
| |
Collapse
|
28
|
Hofherr M, Häuser S, Dewhurst JK, Tengdin P, Sakshath S, Nembach HT, Weber ST, Shaw JM, Silva TJ, Kapteyn HC, Cinchetti M, Rethfeld B, Murnane MM, Steil D, Stadtmüller B, Sharma S, Aeschlimann M, Mathias S. Ultrafast optically induced spin transfer in ferromagnetic alloys. SCIENCE ADVANCES 2020; 6:eaay8717. [PMID: 32010774 PMCID: PMC6968944 DOI: 10.1126/sciadv.aay8717] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 10/09/2019] [Indexed: 05/23/2023]
Abstract
The vision of using light to manipulate electronic and spin excitations in materials on their fundamental time and length scales requires new approaches in experiment and theory to observe and understand these excitations. The ultimate speed limit for all-optical manipulation requires control schemes for which the electronic or magnetic subsystems of the materials are coherently manipulated on the time scale of the laser excitation pulse. In our work, we provide experimental evidence of such a direct, ultrafast, and coherent spin transfer between two magnetic subsystems of an alloy of Fe and Ni. Our experimental findings are fully supported by time-dependent density functional theory simulations and, hence, suggest the possibility of coherently controlling spin dynamics on subfemtosecond time scales, i.e., the birth of the research area of attomagnetism.
Collapse
Affiliation(s)
- M. Hofherr
- Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
- Graduate School of Excellence Materials Science in Mainz, Staudinger Weg 9, 55128 Mainz, Germany
| | - S. Häuser
- Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - J. K. Dewhurst
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - P. Tengdin
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - S. Sakshath
- Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - H. T. Nembach
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - S. T. Weber
- Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - J. M. Shaw
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - T. J. Silva
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - H. C. Kapteyn
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - M. Cinchetti
- Experimentelle Physik VI, Technische Universität Dortmund, 44221 Dortmund, Germany
| | - B. Rethfeld
- Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - M. M. Murnane
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - D. Steil
- Georg-August-Universität Göttingen, I. Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - B. Stadtmüller
- Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
- Graduate School of Excellence Materials Science in Mainz, Staudinger Weg 9, 55128 Mainz, Germany
| | - S. Sharma
- Max Born Institute for Nonlinear Optics, Max-Born-Strasse 2A, 12489 Berlin, Germany
| | - M. Aeschlimann
- Technische Universität Kaiserslautern und Landesforschungszentrum OPTIMAS, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - S. Mathias
- Georg-August-Universität Göttingen, I. Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- Corresponding author.
| |
Collapse
|
29
|
Revealing angular momentum transfer channels and timescales in the ultrafast demagnetization process of ferromagnetic semiconductors. Proc Natl Acad Sci U S A 2019; 116:19258-19263. [PMID: 31501328 DOI: 10.1073/pnas.1907246116] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ultrafast control of magnetic order by light provides a promising realization for spintronic devices beyond Moore's Law and has stimulated intense research interest in recent years. Yet, despite 2 decades of debates, the key question of how the spin angular momentum flows on the femtosecond timescale remains open. The lack of direct first-principle methods and pictures for such process exacerbates the issue. Here, we unravel the laser-induced demagnetization mechanism of ferromagnetic semiconductor GaMnAs, using an efficient time-dependent density functional theory approach that enables the direct real-time snapshot of the demagnetization process. Our results show a clear spin-transfer trajectory from the localized Mn-d electrons to itinerant carriers within 20 fs, illustrating the dominant role of [Formula: see text] interaction. We find that the total spin of localized electrons and itinerant carriers is not conserved in the presence of spin-orbit coupling (SOC). Immediately after laser excitation, a growing percentage of spin-angular momentum is quickly transferred to the electron orbital via SOC in about 1 ps, then slowly to the lattice via electron-phonon coupling in a few picoseconds, responsible for the 2-stage process observed experimentally. The spin-relaxation time via SOC is about 300 fs for itinerant carriers and about 700 fs for Mn-d electrons. These results provide a quantum-mechanical microscopic picture for the long-standing questions regarding the channels and timescales of spin transfer, as well as the roles of different interactions underlying the GaMnAs demagnetization process.
Collapse
|
30
|
Bencivenga F, Mincigrucci R, Capotondi F, Foglia L, Naumenko D, Maznev AA, Pedersoli E, Simoncig A, Caporaletti F, Chiloyan V, Cucini R, Dallari F, Duncan RA, Frazer TD, Gaio G, Gessini A, Giannessi L, Huberman S, Kapteyn H, Knobloch J, Kurdi G, Mahne N, Manfredda M, Martinelli A, Murnane M, Principi E, Raimondi L, Spampinati S, Spezzani C, Trovò M, Zangrando M, Chen G, Monaco G, Nelson KA, Masciovecchio C. Nanoscale transient gratings excited and probed by extreme ultraviolet femtosecond pulses. SCIENCE ADVANCES 2019; 5:eaaw5805. [PMID: 31360768 PMCID: PMC6660206 DOI: 10.1126/sciadv.aaw5805] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 06/20/2019] [Indexed: 05/27/2023]
Abstract
Advances in developing ultrafast coherent sources operating at extreme ultraviolet (EUV) and x-ray wavelengths allow the extension of nonlinear optical techniques to shorter wavelengths. Here, we describe EUV transient grating spectroscopy, in which two crossed femtosecond EUV pulses produce spatially periodic nanoscale excitations in the sample and their dynamics is probed via diffraction of a third time-delayed EUV pulse. The use of radiation with wavelengths down to 13.3 nm allowed us to produce transient gratings with periods as short as 28 nm and observe thermal and coherent phonon dynamics in crystalline silicon and amorphous silicon nitride. This approach allows measurements of thermal transport on the ~10-nm scale, where the two samples show different heat transport regimes, and can be applied to study other phenomena showing nontrivial behaviors at the nanoscale, such as structural relaxations in complex liquids and ultrafast magnetic dynamics.
Collapse
Affiliation(s)
- F. Bencivenga
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - R. Mincigrucci
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - F. Capotondi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - L. Foglia
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - D. Naumenko
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - A. A. Maznev
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - E. Pedersoli
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - A. Simoncig
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - F. Caporaletti
- Department of Physics, University of Trento, Via Sommarive 14, Povo (TN), Italy
| | - V. Chiloyan
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - R. Cucini
- IOM-CNR, Strada Statale 14, km 163.5, in Area Science Park, I-34012 Basovizza (TS), Italy
| | - F. Dallari
- Department of Physics, University of Trento, Via Sommarive 14, Povo (TN), Italy
| | - R. A. Duncan
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - T. D. Frazer
- JILA and Department of Physics, University of Colorado, Boulder, CO 80309, USA
| | - G. Gaio
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - A. Gessini
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - L. Giannessi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - S. Huberman
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - H. Kapteyn
- JILA and Department of Physics, University of Colorado, Boulder, CO 80309, USA
| | - J. Knobloch
- JILA and Department of Physics, University of Colorado, Boulder, CO 80309, USA
| | - G. Kurdi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - N. Mahne
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
- IOM-CNR, Strada Statale 14, km 163.5, in Area Science Park, I-34012 Basovizza (TS), Italy
| | - M. Manfredda
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - A. Martinelli
- Department of Physics, University of Trento, Via Sommarive 14, Povo (TN), Italy
| | - M. Murnane
- JILA and Department of Physics, University of Colorado, Boulder, CO 80309, USA
| | - E. Principi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - L. Raimondi
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - S. Spampinati
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - C. Spezzani
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - M. Trovò
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| | - M. Zangrando
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
- IOM-CNR, Strada Statale 14, km 163.5, in Area Science Park, I-34012 Basovizza (TS), Italy
| | - G. Chen
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - G. Monaco
- Department of Physics, University of Trento, Via Sommarive 14, Povo (TN), Italy
| | - K. A. Nelson
- Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - C. Masciovecchio
- Elettra Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza (TS), Italy
| |
Collapse
|
31
|
Measuring the atomic spin-flip scattering rate by x-ray emission spectroscopy. Sci Rep 2019; 9:8977. [PMID: 31222052 PMCID: PMC6586882 DOI: 10.1038/s41598-019-45242-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/31/2019] [Indexed: 11/23/2022] Open
Abstract
While extensive work has been dedicated to the measurement of the demagnetization time following an ultra-short laser pulse, experimental studies of its underlying microscopic mechanisms are still scarce. In transition metal ferromagnets, one of the main mechanism is the spin-flip of conduction electrons driven by electron-phonon scattering. Here, we present an original experimental method to monitor the electron-phonon mediated spin-flip scattering rate in nickel through the stringent atomic symmetry selection rules of x-ray emission spectroscopy. Increasing the phonon population leads to a waning of the 3d → 2p3/2 decay peak intensity, which reflects an increase of the angular momentum transfer scattering rate attributed to spin-flip. We find a spin relaxation time scale in the order of 50 fs in the 3d-band of nickel at room temperature, while consistantly, no such peak evolution is observed for the diamagnetic counterexample copper, using the same method.
Collapse
|
32
|
Chen Z, Wang LW. Role of initial magnetic disorder: A time-dependent ab initio study of ultrafast demagnetization mechanisms. SCIENCE ADVANCES 2019; 5:eaau8000. [PMID: 31259238 PMCID: PMC6598756 DOI: 10.1126/sciadv.aau8000] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 05/22/2019] [Indexed: 05/23/2023]
Abstract
Despite more than 20 years of development, the underlying physics of the laser-induced demagnetization process is still debated. We present a fast, real-time time-dependent density functional theory (rt-TDDFT) algorithm together with the phenomenological atomic Landau-Lifshitz-Gilbert model to investigate this problem. Our Hamiltonian considers noncollinear magnetic moment, spin-orbit coupling (SOC), electron-electron, electron-phonon, and electron-light interactions. The algorithm for time evolution achieves hundreds of times of speedup enabling calculation of large systems. Our simulations yield a demagnetization rate similar to experiments. We found that (i) the angular momentum flow from light to the system is not essential and the spin Zeeman effect is negligible. (ii) The phonon can play a role but is not essential. (iii) The initial spin disorder and the self-consistent update of the electron-electron interaction play dominant roles and enhance the demagnetization to the experimentally observed rate. The spin disorder connects the electronic structure theory with the phenomenological three-temperature model.
Collapse
|
33
|
Wang CY, Elliott P, Sharma S, Dewhurst JK. Real time scissor correction in TD-DFT. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:214002. [PMID: 30721894 DOI: 10.1088/1361-648x/ab048a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We demonstrate how the scissor correction to the optical band gap, common in linear-response time-dependent density functional theory (TD-DFT), may be extended to the domain of real-time TD-DFT. This requires modifying both the eigenvalues and momentum matrix elements of the underlying basis set. It provides a simple and computationally economical approach for calculating accurate electron dynamics in solids. We demonstrate the importance of this correction for prototypical semiconductors, diamond and silicon, where the energy absorption in both the linear and non-linear regimes is examined. We also show that for a particular system, ZnSe, using the adiabatic local density approximation together with a scissor correction can be advantageous over other approximations, as the underlying quasi-particle band structure is more accurate.
Collapse
Affiliation(s)
- C-Y Wang
- Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
| | | | | | | |
Collapse
|
34
|
Alekhin A, Razdolski I, Berritta M, Bürstel D, Temnov V, Diesing D, Bovensiepen U, Woltersdorf G, Oppeneer PM, Melnikov A. Magneto-optical properties of Au upon the injection of hot spin-polarized electrons across Fe/Au(0 0 1) interfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:124002. [PMID: 30625433 DOI: 10.1088/1361-648x/aafd06] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We demonstrate a novel method for the excitation of sizable magneto-optical effects in Au by means of the laser-induced injection of hot spin-polarized electrons in Au/Fe/MgO(0 0 1) heterostructures. It is based on the energy- and spin-dependent electron transmittance of Fe/Au interface which acts as a spin filter for non-thermalized electrons optically excited in Fe. We show that after crossing the interface, majority electrons propagate through the Au layer with the velocity on the order of 1 nm fs-1 (close to the Fermi velocity) and the decay length on the order of 100 nm. Featuring ultrafast functionality and requiring no strong external magnetic fields, spin injection results in a distinct magneto-optical response of Au. We develop a formalism based on the phase of the transient complex MOKE response and demonstrate its robustness in a plethora of experimental and theoretical MOKE studies on Au, including our ab initio calculations. Our work introduces a flexible tool to manipulate magneto-optical properties of metals on the femtosecond timescale that holds high potential for active magneto-photonics, plasmonics, and spintronics.
Collapse
Affiliation(s)
- A Alekhin
- Institute of Molecules and Materials of Le Mans, CNRS UMR 6283, 72085 Le Mans, France
| | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Chen J, Bovensiepen U, Eschenlohr A, Müller T, Elliott P, Gross EKU, Dewhurst JK, Sharma S. Competing Spin Transfer and Dissipation at Co/Cu(001) Interfaces on Femtosecond Timescales. PHYSICAL REVIEW LETTERS 2019; 122:067202. [PMID: 30822073 DOI: 10.1103/physrevlett.122.067202] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 11/28/2018] [Indexed: 05/23/2023]
Abstract
By combining interface-sensitive nonlinear magneto-optical experiments with femtosecond time resolution and ab initio time-dependent density functional theory, we show that optically excited spin dynamics at Co/Cu(001) interfaces proceeds via spin-dependent charge transfer and back transfer between Co and Cu. This ultrafast spin transfer competes with dissipation of spin angular momentum mediated by spin-orbit coupling already on sub 100 fs timescales. We thereby identify the fundamental microscopic processes during laser-induced spin transfer at a model interface for technologically relevant ferromagnetic heterostructures.
Collapse
Affiliation(s)
- J Chen
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
| | - U Bovensiepen
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
| | - A Eschenlohr
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
| | - T Müller
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - P Elliott
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - E K U Gross
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - J K Dewhurst
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - S Sharma
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany and Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Strasse 2A, 12489 Berlin, Germany
| |
Collapse
|
36
|
Abstract
The Einstein-de Haas effect was originally observed in a landmark experiment1 demonstrating that the angular momentum associated with aligned electron spins in a ferromagnet can be converted to mechanical angular momentum by reversing the direction of magnetization using an external magnetic field. A related problem concerns the timescale of this angular momentum transfer. Experiments have established that intense photoexcitation in several metallic ferromagnets leads to a drop in magnetization on a timescale shorter than 100 femtoseconds-a phenomenon called ultrafast demagnetization2-4. Although the microscopic mechanism for this process has been hotly debated, the key question of where the angular momentum goes on these femtosecond timescales remains unanswered. Here we use femtosecond time-resolved X-ray diffraction to show that most of the angular momentum lost from the spin system upon laser-induced demagnetization of ferromagnetic iron is transferred to the lattice on sub-picosecond timescales, launching a transverse strain wave that propagates from the surface into the bulk. By fitting a simple model of the X-ray data to simulations and optical data, we estimate that the angular momentum transfer occurs on a timescale of 200 femtoseconds and corresponds to 80 per cent of the angular momentum that is lost from the spin system. Our results show that interaction with the lattice has an essential role in the process of ultrafast demagnetization in this system.
Collapse
|
37
|
Zhang GP, Bai YH, Jenkins T, George TF. Laser-induced ultrafast transport and demagnetization at the earliest time: first-principles and real-time investigation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:465801. [PMID: 30277218 DOI: 10.1088/1361-648x/aae5a9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
It is generally believed that there are at least two ways to use an ultrafast laser pulse to demagnetize a magnetic sample. One is to directly photo-demagnetize the system through spin-orbit coupling (SOC), and the other is to utilize ultrafast hot electron transport without SOC. The challenge is that these two processes are entangled on the same time scale. While the experimental results have been inconclusive, theoretical investigations are even scarcer, beyond those earlier studies based on spin superdiffusion. For instance, we do not even know how fast electrons move under laser excitation and how far they move. Here we carry out a first-principles time-dependent calculation to investigate how fast electrons actually move under laser excitation and how large the electron transport affects demagnetization on the shortest time scale. To take into account the transport effect, we implement the intraband transition in our theory. In the bulk fcc Ni, we find the effect of the spin transport on the demagnetization is extremely small, no more than 1%. The collective electron velocity in Ni is 0.4 Å fs-1, much smaller than the Fermi velocity, and the collective displacement is no more than 0.1 Å. But this does not mean that electrons do not travel fast; instead we find that electron velocities at two opposite crystal momenta cancel each other. We follow the Γ-X line and find a huge dispersion in the velocities in the crystal momentum space. In the Fe/W(1 1 0) thin film, the overall demagnetization is larger than Ni, and the Fermi velocity is higher than Ni. However, the effect of the spin transport is still small in the Fe/W(1 1 0) thin film. Based on our numerical results and existing experimental findings, we propose a different mechanism that can explain two latest experimental results. Our finding sheds new light on the effect of ballistic transport on demagnetization.
Collapse
Affiliation(s)
- G P Zhang
- Department of Physics, Indiana State University, Terre Haute, IN 47809, United States of America
| | | | | | | |
Collapse
|
38
|
Gort R, Bühlmann K, Däster S, Salvatella G, Hartmann N, Zemp Y, Holenstein S, Stieger C, Fognini A, Michlmayr TU, Bähler T, Vaterlaus A, Acremann Y. Early Stages of Ultrafast Spin Dynamics in a 3d Ferromagnet. PHYSICAL REVIEW LETTERS 2018; 121:087206. [PMID: 30192573 DOI: 10.1103/physrevlett.121.087206] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 07/24/2018] [Indexed: 06/08/2023]
Abstract
Prior to the development of pulsed lasers, one assigned a single local temperature to the lattice, the electron gas, and the spins. With the availability of ultrafast laser sources, one can now drive the temperature of these reservoirs out of equilibrium. Thus, the solid shows new internal degrees of freedom characterized by individual temperatures of the electron gas T_{e}, the lattice T_{l} and the spins T_{s}. We demonstrate an analogous behavior in the spin polarization of a ferromagnet in an ultrafast demagnetization experiment: At the Fermi energy, the polarization is reduced faster than at deeper in the valence band. Therefore, on the femtosecond time scale, the magnetization as a macroscopic quantity does not provide the full picture of the spin dynamics: The spin polarization separates into different parts similar to how the single temperature paradigm changed with the development of ultrafast lasers.
Collapse
Affiliation(s)
- R Gort
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - K Bühlmann
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - S Däster
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - G Salvatella
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - N Hartmann
- Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland
| | - Y Zemp
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - S Holenstein
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Department of Physics, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - C Stieger
- Department of Information Technology and Electrical Engineering, ETH Zurich, 8092 Zurich, Switzerland
| | - A Fognini
- Department of Quantum Nanoscience, TU Delft, 2628 CD Delft, Netherlands
| | - T U Michlmayr
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - T Bähler
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - A Vaterlaus
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Y Acremann
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| |
Collapse
|
39
|
Layer specific observation of slow thermal equilibration in ultrathin metallic nanostructures by femtosecond X-ray diffraction. Nat Commun 2018; 9:3335. [PMID: 30127415 PMCID: PMC6102217 DOI: 10.1038/s41467-018-05693-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 05/18/2018] [Indexed: 11/29/2022] Open
Abstract
Ultrafast heat transport in nanoscale metal multilayers is of great interest in the context of optically induced demagnetization, remagnetization and switching. If the penetration depth of light exceeds the bilayer thickness, layer-specific information is unavailable from optical probes. Femtosecond diffraction experiments provide unique experimental access to heat transport over single digit nanometer distances. Here, we investigate the structural response and the energy flow in the ultrathin double-layer system: gold on ferromagnetic nickel. Even though the excitation pulse is incident from the Au side, we observe a very rapid heating of the Ni lattice, whereas the Au lattice initially remains cold. The subsequent heat transfer from Ni to the Au lattice is found to be two orders of magnitude slower than predicted by the conventional heat equation and much slower than electron–phonon coupling times in Au. We present a simplified model calculation highlighting the relevant thermophysical quantities. Heat transport in ultrathin metal layers is important for potential applications in optical‐magnetic switching, but difficult to access experimentally. Here, the authors use ultrafast X‐ray diffraction to directly probe and explain unexpected time‐dependent transport behavior in Au–Ni nanolayers.
Collapse
|
40
|
You W, Tengdin P, Chen C, Shi X, Zusin D, Zhang Y, Gentry C, Blonsky A, Keller M, Oppeneer PM, Kapteyn H, Tao Z, Murnane M. Revealing the Nature of the Ultrafast Magnetic Phase Transition in Ni by Correlating Extreme Ultraviolet Magneto-Optic and Photoemission Spectroscopies. PHYSICAL REVIEW LETTERS 2018; 121:077204. [PMID: 30169091 DOI: 10.1103/physrevlett.121.077204] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Indexed: 06/08/2023]
Abstract
By correlating time- and angle-resolved photoemission and time-resolved transverse magneto-optical Kerr effect measurements, both at extreme ultraviolet wavelengths, we uncover the universal nature of the ultrafast photoinduced magnetic phase transition in Ni. This allows us to explain the ultrafast magnetic response of Ni at all laser fluences-from a small reduction of the magnetization at low laser fluences, to complete quenching at high laser fluences. Both probe methods exhibit the same demagnetization and recovery timescales. The spin system absorbs the energy required to proceed through a magnetic phase transition within 20 fs after the peak of the pump pulse. However, the spectroscopic signatures of demagnetization of the material appear only after ≈200 fs and the subsequent recovery of magnetization on timescales ranging from 500 fs to >70 ps. We also provide evidence of two competing channels with two distinct timescales in the recovery process that suggest the presence of coexisting phases in the material.
Collapse
Affiliation(s)
- Wenjing You
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Phoebe Tengdin
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Cong Chen
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Xun Shi
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Dmitriy Zusin
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Yingchao Zhang
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Christian Gentry
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Adam Blonsky
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Mark Keller
- National Institute of Standards and Technology (NIST), 325 Broadway, Boulder, Colorado 80305, USA
| | - Peter M Oppeneer
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - Henry Kapteyn
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Zhensheng Tao
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| | - Margaret Murnane
- Department of Physics and JILA, University of Colorado and NIST, Boulder, Colorado 80309, USA
| |
Collapse
|
41
|
Bühlmann K, Gort R, Salvatella G, Däster S, Fognini A, Bähler T, Dornes C, Vaz CAF, Vaterlaus A, Acremann Y. Ultrafast demagnetization in iron: Separating effects by their nonlinearity. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2018; 5:044502. [PMID: 30175157 PMCID: PMC6105339 DOI: 10.1063/1.5040344] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 08/10/2018] [Indexed: 06/07/2023]
Abstract
The laser-driven ultrafast demagnetization effect is one of the long-standing problems in solid-state physics. The time scale is given not only by the transfer of energy, but also by the transport of angular momentum away from the spin system. Through a double-pulse experiment resembling two-dimensional spectroscopy, we separate the different pathways by their nonlinear properties. We find (a) that the loss of magnetization within 400 fs is not affected by the previous excitations (linear process), and (b) we observe a picosecond demagnetization contribution that is strongly affected by the previous excitations. Our experimental approach is useful not only for studying femtosecond spin dynamics, but can also be adapted to other problems in solid-state dynamics.
Collapse
Affiliation(s)
- Kevin Bühlmann
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Rafael Gort
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Gerard Salvatella
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Simon Däster
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | | | - Thomas Bähler
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Christian Dornes
- Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland
| | - C A F Vaz
- Swiss Light Source, Paul Scherrer Institut, PSI, 5232 Villigen, Switzerland
| | - Andreas Vaterlaus
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| | - Yves Acremann
- Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich, Switzerland
| |
Collapse
|
42
|
Tengdin P, You W, Chen C, Shi X, Zusin D, Zhang Y, Gentry C, Blonsky A, Keller M, Oppeneer PM, Kapteyn HC, Tao Z, Murnane MM. Critical behavior within 20 fs drives the out-of-equilibrium laser-induced magnetic phase transition in nickel. SCIENCE ADVANCES 2018; 4:eaap9744. [PMID: 29511738 PMCID: PMC5834307 DOI: 10.1126/sciadv.aap9744] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 01/31/2018] [Indexed: 05/23/2023]
Abstract
It has long been known that ferromagnets undergo a phase transition from ferromagnetic to paramagnetic at the Curie temperature, associated with critical phenomena such as a divergence in the heat capacity. A ferromagnet can also be transiently demagnetized by heating it with an ultrafast laser pulse. However, to date, the connection between out-of-equilibrium and equilibrium phase transitions, or how fast the out-of-equilibrium phase transitions can proceed, was not known. By combining time- and angle-resolved photoemission with time-resolved transverse magneto-optical Kerr spectroscopies, we show that the same critical behavior also governs the ultrafast magnetic phase transition in nickel. This is evidenced by several observations. First, we observe a divergence of the transient heat capacity of the electron spin system preceding material demagnetization. Second, when the electron temperature is transiently driven above the Curie temperature, we observe an extremely rapid change in the material response: The spin system absorbs sufficient energy within the first 20 fs to subsequently proceed through the phase transition, whereas demagnetization and the collapse of the exchange splitting occur on much longer, fluence-independent time scales of ~176 fs. Third, we find that the transient electron temperature alone dictates the magnetic response. Our results are important because they connect the out-of-equilibrium material behavior to the strongly coupled equilibrium behavior and uncover a new time scale in the process of ultrafast demagnetization.
Collapse
Affiliation(s)
- Phoebe Tengdin
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Wenjing You
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Cong Chen
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Xun Shi
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Dmitriy Zusin
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Yingchao Zhang
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Christian Gentry
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Adam Blonsky
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | | | - Peter M. Oppeneer
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
| | - Henry C. Kapteyn
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Zhensheng Tao
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| | - Margaret M. Murnane
- Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology (NIST), Boulder, CO 80309, USA
| |
Collapse
|
43
|
Malvestuto M, Ciprian R, Caretta A, Casarin B, Parmigiani F. Ultrafast magnetodynamics with free-electron lasers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:053002. [PMID: 29315080 DOI: 10.1088/1361-648x/aaa211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The study of ultrafast magnetodynamics has entered a new era thanks to the groundbreaking technological advances in free-electron laser (FEL) light sources. The advent of these light sources has made possible unprecedented experimental schemes for time-resolved x-ray magneto-optic spectroscopies, which are now paving the road for exploring the ultimate limits of out-of-equilibrium magnetic phenomena. In particular, these studies will provide insights into elementary mechanisms governing spin and orbital dynamics, therefore contributing to the development of ultrafast devices for relevant magnetic technologies. This topical review focuses on recent advancement in the study of non-equilibrium magnetic phenomena from the perspective of time-resolved extreme ultra violet (EUV) and soft x-ray spectroscopies at FELs with highlights of some important experimental results.
Collapse
Affiliation(s)
- Marco Malvestuto
- Elettra-Sincrotrone Trieste S.C.p.A. Strada Statale 14-km 163.5 in AREA Science Park 34149 Basovizza, Trieste, Italy
| | | | | | | | | |
Collapse
|
44
|
Hoveyda F, Hohenstein E, Judge R, Smadici S. Demagnetizing fields in all-optical switching. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:035801. [PMID: 29185999 DOI: 10.1088/1361-648x/aa9e39] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A model of demagnetizing fields and micromagnetic simulations are applied to examine the evolution of a demagnetized cylinder. In addition to three expected final magnetic structures, a fourth switched state is obtained over a range of magnetic energy densities. The switched state is absent when demagnetizing fields are neglected. The connection to all-optical switching of materials with perpendicular magnetic anisotropy is discussed.
Collapse
Affiliation(s)
- F Hoveyda
- Department of Physics and Astronomy, University of Louisville, KY 40292, United States of America
| | | | | | | |
Collapse
|
45
|
Thielemann-Kühn N, Schick D, Pontius N, Trabant C, Mitzner R, Holldack K, Zabel H, Föhlisch A, Schüßler-Langeheine C. Ultrafast and Energy-Efficient Quenching of Spin Order: Antiferromagnetism Beats Ferromagnetism. PHYSICAL REVIEW LETTERS 2017; 119:197202. [PMID: 29219516 DOI: 10.1103/physrevlett.119.197202] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Indexed: 06/07/2023]
Abstract
By comparing femtosecond laser pulse induced ferro- and antiferromagnetic dynamics in one and the same material-metallic dysprosium-we show both to behave fundamentally different. Antiferromagnetic order is considerably faster and much more efficiently reduced by optical excitation than its ferromagnetic counterpart. We assign the fast and extremely efficient process in the antiferromagnet to an interatomic transfer of angular momentum within the spin system. Our findings imply that this angular momentum transfer channel is effective in other magnetic metals with nonparallel spin alignment. They also point out a possible route towards energy-efficient spin manipulation for magnetic devices.
Collapse
Affiliation(s)
- Nele Thielemann-Kühn
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
| | - Daniel Schick
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Niko Pontius
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Christoph Trabant
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
| | - Rolf Mitzner
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Karsten Holldack
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - Hartmut Zabel
- Institut für Physik, Johannes-Gutenberg-Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Alexander Föhlisch
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
| | - Christian Schüßler-Langeheine
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| |
Collapse
|
46
|
Sant T, Ksenzov D, Capotondi F, Pedersoli E, Manfredda M, Kiskinova M, Zabel H, Kläui M, Lüning J, Pietsch U, Gutt C. Measurements of ultrafast spin-profiles and spin-diffusion properties in the domain wall area at a metal/ferromagnetic film interface. Sci Rep 2017; 7:15064. [PMID: 29118451 PMCID: PMC5678147 DOI: 10.1038/s41598-017-15234-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 10/23/2017] [Indexed: 11/25/2022] Open
Abstract
Exciting a ferromagnetic material with an ultrashort IR laser pulse is known to induce spin dynamics by heating the spin system and by ultrafast spin diffusion processes. Here, we report on measurements of spin-profiles and spin diffusion properties in the vicinity of domain walls in the interface region between a metallic Al layer and a ferromagnetic Co/Pd thin film upon IR excitation. We followed the ultrafast temporal evolution by means of an ultrafast resonant magnetic scattering experiment in surface scattering geometry, which enables us to exploit the evolution of the domain network within a 1/e distance of 3 nm to 5 nm from the Al/FM film interface. We observe a magnetization-reversal close to the domain wall boundaries that becomes more pronounced closer to the Al/FM film interface. This magnetization-reversal is driven by the different transport properties of majority and minority carriers through a magnetically disordered domain network. Its finite lateral extension has allowed us to measure the ultrafast spin-diffusion coefficients and ultrafast spin velocities for majority and minority carriers upon IR excitation.
Collapse
Affiliation(s)
- T Sant
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, D-57072, Siegen, Germany
| | - D Ksenzov
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, D-57072, Siegen, Germany
| | - F Capotondi
- FERMI, Elettra-Sincrotrone Trieste, 34149, Basovizza, Trieste, Italy
| | - E Pedersoli
- FERMI, Elettra-Sincrotrone Trieste, 34149, Basovizza, Trieste, Italy
| | - M Manfredda
- FERMI, Elettra-Sincrotrone Trieste, 34149, Basovizza, Trieste, Italy
| | - M Kiskinova
- FERMI, Elettra-Sincrotrone Trieste, 34149, Basovizza, Trieste, Italy
| | - H Zabel
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099, Mainz, Germany
| | - M Kläui
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099, Mainz, Germany
| | - J Lüning
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Chimie Physique - Matière et Rayonnement, 75005, Paris, France
| | - U Pietsch
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, D-57072, Siegen, Germany
| | - C Gutt
- Department Physik, Universität Siegen, Walter-Flex-Strasse 3, D-57072, Siegen, Germany.
| |
Collapse
|
47
|
Eschenlohr A, Persichetti L, Kachel T, Gabureac M, Gambardella P, Stamm C. Spin currents during ultrafast demagnetization of ferromagnetic bilayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:384002. [PMID: 28678017 DOI: 10.1088/1361-648x/aa7dd3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Ultrafast spin currents induced by femtosecond laser excitation of ferromagnetic metals have been found to contribute to sub-picosecond demagnetization, and to cause a transient enhancement of the magnetization of the bottom Fe layer in a Ni/Ru/Fe layered structure. We analyze the ultrafast magnetization dynamics in such layered structures by element- and femtosecond time-resolved x-ray magnetic circular dichroism, for different Ni and Fe layer thicknesses, Ru and Ta interlayers, and by varying the pump laser fluence. While we do not observe the transient enhancement of the magnetization in Ni/Ru/Fe discovered previously, we do find a reduced demagnetization of the Fe layer compared to a Ni/Ta/Fe layered structure. In the latter, the spin-scattering Ta layer suppresses spin currents from the Ni layer into Fe, consistent with previous results. Any spin current arriving in the lower Fe layer will counteract other, local demagnetization mechanisms such as phonon-mediated spin-flip scattering. We find by increasing the Ni and Fe layer thicknesses in Ni/Ru/Fe a decreasing effect of spin currents on the buried Fe layer, consistent with a mean free path of the laser-induced spin currents of just a few nm. Our results suggest that in order to utilize ultrafast spin currents in an efficient manner, the sample design has to be optimized with these considerations in mind, and further studies clarifying the role of interfaces in the employed layered structures are needed.
Collapse
Affiliation(s)
- A Eschenlohr
- Fakultät für Physik, Universität Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany
| | | | | | | | | | | |
Collapse
|
48
|
Shokeen V, Sanchez Piaia M, Bigot JY, Müller T, Elliott P, Dewhurst JK, Sharma S, Gross EKU. Spin Flips versus Spin Transport in Nonthermal Electrons Excited by Ultrashort Optical Pulses in Transition Metals. PHYSICAL REVIEW LETTERS 2017; 119:107203. [PMID: 28949167 DOI: 10.1103/physrevlett.119.107203] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Indexed: 05/23/2023]
Abstract
A joint theoretical and experimental investigation is performed to understand the underlying physics of laser-induced demagnetization in Ni and Co films with varying thicknesses excited by 10 fs optical pulses. Experimentally, the dynamics of spins is studied by determining the time-dependent amplitude of the Voigt vector, retrieved from a full set of magnetic and nonmagnetic quantities performed on both sides of films, with absolute time reference. Theoretically, ab initio calculations are performed using time-dependent density functional theory. Overall, we demonstrate that spin-orbit induced spin flips are the most significant contributors with superdiffusive spin transport, which assumes only that the transport of majority spins without spin flips induced by scattering does not apply in Ni. In Co it plays a significant role during the first ∼20 fs only. Our study highlights the material dependent nature of the demagnetization during the process of thermalization of nonequilibrium spins.
Collapse
Affiliation(s)
- V Shokeen
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504, 67034 Strasbourg, France
| | - M Sanchez Piaia
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504, 67034 Strasbourg, France
| | - J-Y Bigot
- Université de Strasbourg, CNRS, Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504, 67034 Strasbourg, France
| | - T Müller
- Max-Planck Institut für Microstrukture Physics, Weinberg 2, D-06120 Halle, Germany
| | - P Elliott
- Max-Planck Institut für Microstrukture Physics, Weinberg 2, D-06120 Halle, Germany
| | - J K Dewhurst
- Max-Planck Institut für Microstrukture Physics, Weinberg 2, D-06120 Halle, Germany
| | - S Sharma
- Max-Planck Institut für Microstrukture Physics, Weinberg 2, D-06120 Halle, Germany
| | - E K U Gross
- Max-Planck Institut für Microstrukture Physics, Weinberg 2, D-06120 Halle, Germany
| |
Collapse
|
49
|
Alekhin A, Razdolski I, Ilin N, Meyburg JP, Diesing D, Roddatis V, Rungger I, Stamenova M, Sanvito S, Bovensiepen U, Melnikov A. Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves. PHYSICAL REVIEW LETTERS 2017; 119:017202. [PMID: 28731774 DOI: 10.1103/physrevlett.119.017202] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Indexed: 05/23/2023]
Abstract
Using the sensitivity of optical second harmonic generation to currents, we demonstrate the generation of 250-fs long spin current pulses in Fe/Au/Fe/MgO(001) spin valves. The temporal profile of these pulses indicates ballistic transport of hot electrons across a sub-100 nm Au layer. The pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe/Au interface transmittance we conclude that a nonthermal spin-dependent Seebeck effect is responsible for the generation of ultrashort spin current pulses. The demonstrated rotation of spin polarization of hot electrons upon interaction with noncollinear magnetization at Au/Fe interfaces holds high potential for future spintronic devices.
Collapse
Affiliation(s)
- Alexandr Alekhin
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Ilya Razdolski
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Nikita Ilin
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
| | - Jan P Meyburg
- Faculty of Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45117 Essen, Germany
| | - Detlef Diesing
- Faculty of Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45117 Essen, Germany
| | - Vladimir Roddatis
- Institute of Materials Physics, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen, Germany
| | - Ivan Rungger
- School of Physics and CRANN, Trinity College Dublin, Dublin 2, Ireland
| | - Maria Stamenova
- School of Physics and CRANN, Trinity College Dublin, Dublin 2, Ireland
| | - Stefano Sanvito
- School of Physics and CRANN, Trinity College Dublin, Dublin 2, Ireland
| | - Uwe Bovensiepen
- Faculty of Physics, University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany
| | - Alexey Melnikov
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin, Germany
- Institute of Physics, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle, Germany
| |
Collapse
|
50
|
Bierbrauer U, Weber ST, Schummer D, Barkowski M, Mahro AK, Mathias S, Christian Schneider H, Stadtmüller B, Aeschlimann M, Rethfeld B. Ultrafast magnetization dynamics in Nickel: impact of pump photon energy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:244002. [PMID: 28510535 DOI: 10.1088/1361-648x/aa6f73] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Magnetization dynamics on a femtosecond timescale has been observed for a huge variety of magnetic structures. However, the influence of different excitation photon energies has not been studied in detail yet. In our time-resolved magneto-optical Kerr effect setup we excite a Nickel bulk system with 1.55 and 3.1 eV, respectively, leading to different remagnetization dynamics depending on the chosen photon energy. Furthermore we complement our experimental data with a theoretical approach applying appropriate Boltzmann collision integrals including the density of states of Nickel. The comparison between the experimental data and the theoretical approach indicates that photon-energy dependent transport processes play a major role in this setup.
Collapse
Affiliation(s)
- Ute Bierbrauer
- Department of Physics and OPTIMAS Research Center, University of Kaiserslautern, Erwin-Schrödinger-Strasse 46, 67663 Kaiserslautern, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|