1
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Ukleev V, Leroy L, Mincigrucci R, De Angelis D, Fainozzi D, Khatu NN, Paltanin E, Foglia L, Bencivenga F, Luo C, Ruske F, Radu F, Svetina C, Staub U. Transient grating spectroscopy on a DyCo 5 thin film with femtosecond extreme ultraviolet pulses. Struct Dyn 2024; 11:025101. [PMID: 38476300 PMCID: PMC10929737 DOI: 10.1063/4.0000223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 02/13/2024] [Indexed: 03/14/2024]
Abstract
Surface acoustic waves (SAWs) are excited by femtosecond extreme ultraviolet (EUV) transient gratings (TGs) in a room-temperature ferrimagnetic DyCo5 alloy. TGs are generated by crossing a pair of EUV pulses from a free electron laser with the wavelength of 20.8 nm matching the Co M-edge, resulting in a SAW wavelength of Λ = 44 nm. Using the pump-probe transient grating scheme in reflection geometry, the excited SAWs could be followed in the time range of -10 to 100 ps in the thin film. Coherent generation of TGs by ultrafast EUV pulses allows to excite SAW in any material and to investigate their couplings to other dynamics, such as spin waves and orbital dynamics. In contrast, we encountered challenges in detecting electronic and magnetic signals, potentially due to the dominance of the larger SAW signal and the weakened reflection signal from underlying layers. A potential solution for the latter challenge involves employing soft x-ray probes, albeit introducing additional complexities associated with the required grazing incidence geometry.
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Affiliation(s)
- Victor Ukleev
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-12489 Berlin, Germany
| | - Ludmila Leroy
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | | | - Dario De Angelis
- Elettra—Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Trieste, Italy
| | - Danny Fainozzi
- Elettra—Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Trieste, Italy
| | | | - Ettore Paltanin
- Elettra—Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Trieste, Italy
| | - Laura Foglia
- Elettra—Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Trieste, Italy
| | | | - Chen Luo
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-12489 Berlin, Germany
| | - Florian Ruske
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-12489 Berlin, Germany
| | - Florin Radu
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-12489 Berlin, Germany
| | | | - Urs Staub
- Swiss Light Source, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
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2
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Ukleev V, Khassanov A, Snigireva I, Konovalov O, Vorobiev A. Mesoscale self-organization of polydisperse magnetic nanoparticles at the water surface. J Chem Phys 2024; 160:074703. [PMID: 38364006 DOI: 10.1063/5.0190550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 01/24/2024] [Indexed: 02/18/2024] Open
Abstract
In this study, we investigated the self-ordering process in Langmuir films of polydisperse iron oxide nanoparticles on a water surface, employing in situ x-ray scattering, surface pressure-area isotherm analysis, and Brewster angle microscopy. X-ray reflectometry confirmed the formation of a monolayer, while grazing incidence small-angle x-ray scattering revealed short-range lateral correlations with a characteristic length equal to the mean particle size. Remarkably, our findings indicated that at zero surface pressure, the particles organized into submicrometer clusters, merging upon compression to form a homogeneous layer. These layers were subsequently transferred to a solid substrate using the Langmuir-Schaefer technique and further characterized via scanning electron microscopy and polarized neutron reflectometry. Notably, our measurements revealed a second characteristic length in the lateral correlations, orders of magnitude longer than the mean particle diameter, with polydisperse particles forming circular clusters densely packed in a hexagonal lattice. Furthermore, our evidence suggests that the lattice constant of this mesocrystal depends on the characteristics of the particle size distribution, specifically the mean particle size and the width of the size distribution. In addition, we observed internal size separation within these clusters, where larger particles were positioned closer to the center of the cluster. Finally, polarized neutron reflectometry measurements provided valuable insights into the magnetization profile across the layer.
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Affiliation(s)
- Victor Ukleev
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany
| | - Artoem Khassanov
- Institute of Polymer Materials of the Department of Materials Science Friedrich-Alexander University Erlangen-Nürnberg Martensstrasse 7, D-91058 Erlangen, Germany
- European Synchrotron Radiation Facility, 71, Avenue des Martyrs, CS40220, F-38043 Grenoble CEDEX 9, France
| | - Irina Snigireva
- European Synchrotron Radiation Facility, 71, Avenue des Martyrs, CS40220, F-38043 Grenoble CEDEX 9, France
| | - Oleg Konovalov
- European Synchrotron Radiation Facility, 71, Avenue des Martyrs, CS40220, F-38043 Grenoble CEDEX 9, France
| | - Alexei Vorobiev
- European Synchrotron Radiation Facility, 71, Avenue des Martyrs, CS40220, F-38043 Grenoble CEDEX 9, France
- Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
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3
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Ukleev V, Ajejas F, Devishvili A, Vorobiev A, Steinke NJ, Cubitt R, Luo C, Abrudan RM, Radu F, Cros V, Reyren N, White JS. Observation by SANS and PNR of pure Néel-type domain wall profiles and skyrmion suppression below room temperature in magnetic [Pt/CoFeB/Ru] 10 multilayers. Sci Technol Adv Mater 2024; 25:2315015. [PMID: 38455384 PMCID: PMC10919321 DOI: 10.1080/14686996.2024.2315015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 01/29/2024] [Indexed: 03/09/2024]
Abstract
We report investigations of the magnetic textures in periodic multilayers [Pt(1 nm)/(CoFeB(0.8 nm)/Ru(1.4 nm)]10 using polarised neutron reflectometry (PNR) and small-angle neutron scattering (SANS). The multilayers are known to host skyrmions stabilized by Dzyaloshinskii-Moriya interactions induced by broken inversion symmetry and spin-orbit coupling at the asymmetric interfaces. From depth-dependent PNR measurements, we observed well-defined structural features and obtained the layer-resolved magnetization profiles. The in-plane magnetization of the CoFeB layers calculated from fitting of the PNR profiles is found to be in excellent agreement with magnetometry data. Using SANS as a bulk probe of the entire multilayer, we observe long-period magnetic stripe domains and skyrmion ensembles with full orientational disorder at room temperature. No sign of skyrmions is found below 250 K, which we suggest is due to an increase of an effective magnetic anisotropy in the CoFeB layer on cooling that suppresses skyrmion stability. Using polarised SANS at room temperature, we prove the existence of pure Néel-type windings in both stripe domain and skyrmion regimes. No Bloch-type winding admixture, i.e. an indication for hybrid windings, is detected within the measurement sensitivity, in good agreement with expectations according to our micromagnetic modelling of the multilayers. Our findings using neutron techniques provide valuable microscopic insights into the rich magnetic behavior of skyrmion-hosting multilayers, which are essential for the advancement of future skyrmion-based spintronic devices.
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Affiliation(s)
- Victor Ukleev
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), Villigen, Switzerland
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - Fernando Ajejas
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | | | - Alexei Vorobiev
- Institut Laue-Langevin, Grenoble, France
- Department of Physics, Uppsala University, Uppsala, Sweden
| | | | | | - Chen Luo
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | | | - Florin Radu
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - Vincent Cros
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Nicolas Reyren
- Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay, Palaiseau, France
| | - Jonathan S. White
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), Villigen, Switzerland
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4
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Liu J, Gao X, Shi K, Zhang M, Wu J, Ukleev V, Radu F, Ji Y, Deng Z, Wei L, Hong Y, Hu S, Xiao W, Li L, Zhang Q, Wang Z, Wang L, Gan Y, Chen K, Liao Z. Hundred-Fold Enhancement in the Anomalous Hall Effect Induced by Hydrogenation. Nano Lett 2024; 24:1351-1359. [PMID: 38251855 DOI: 10.1021/acs.nanolett.3c04368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
The anomalous Hall effect (AHE) is one of the most fascinating transport properties in condensed matter physics. However, the AHE magnitude, which mainly depends on net spin polarization and band topology, is generally small in oxides and thus limits potential applications. Here, we demonstrate a giant enhancement of AHE in a LaCoO3-induced 5d itinerant ferromagnet SrIrO3 by hydrogenation. The anomalous Hall resistivity and anomalous Hall angle, which are two of the most critical parameters in AHE-based devices, are found to increase to 62.2 μΩ·cm and 3%, respectively, showing an unprecedentedly large enhancement ratio of ∼10000%. Theoretical analysis suggests the key roles of Berry curvature in enhancing AHE. Furthermore, the hydrogenation concomitantly induces the significant elevation of Curie temperature from 75 to 160 K and 40-fold reinforcement of coercivity. Such giant regulation and very large AHE magnitude observed in SrIrO3 could pave the path for 5d oxide devices.
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Affiliation(s)
- Junhua Liu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Xiaofei Gao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Ke Shi
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei 230031, China
| | - Minjie Zhang
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei 230031, China
| | - Jiating Wu
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei 230031, China
| | - Victor Ukleev
- Helmholtz-Zentrum-Berlin für Materialien und Energie, Albert-Einstein-Straße 15, Berlin 12489, Germany
| | - Florin Radu
- Helmholtz-Zentrum-Berlin für Materialien und Energie, Albert-Einstein-Straße 15, Berlin 12489, Germany
| | - Yaoyao Ji
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Zhixiong Deng
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Long Wei
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Yuhao Hong
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Shilin Hu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Wen Xiao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Lin Li
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Qinghua Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhaosheng Wang
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei 230031, China
| | - Lingfei Wang
- Hefei National Research Center for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Yulin Gan
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Kai Chen
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
| | - Zhaoliang Liao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
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5
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Singh D, Fujishiro Y, Hayami S, Moody SH, Nomoto T, Baral PR, Ukleev V, Cubitt R, Steinke NJ, Gawryluk DJ, Pomjakushina E, Ōnuki Y, Arita R, Tokura Y, Kanazawa N, White JS. Transition between distinct hybrid skyrmion textures through their hexagonal-to-square crystal transformation in a polar magnet. Nat Commun 2023; 14:8050. [PMID: 38052859 DOI: 10.1038/s41467-023-43814-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 11/21/2023] [Indexed: 12/07/2023] Open
Abstract
Magnetic skyrmions, topological vortex-like spin textures, garner significant interest due to their unique properties and potential applications in nanotechnology. While they typically form a hexagonal crystal with distinct internal magnetisation textures known as Bloch- or Néel-type, recent theories suggest the possibility for direct transitions between skyrmion crystals of different lattice structures and internal textures. To date however, experimental evidence for these potentially useful phenomena have remained scarce. Here, we discover the polar tetragonal magnet EuNiGe3 to host two hybrid skyrmion phases, each with distinct internal textures characterised by anisotropic combinations of Bloch- and Néel-type windings. Variation of the magnetic field drives a direct transition between the two phases, with the modification of the hybrid texture concomitant with a hexagonal-to-square skyrmion crystal transformation. We explain these observations with a theory that includes the key ingredients of momentum-resolved Ruderman-Kittel-Kasuya-Yosida and Dzyaloshinskii-Moriya interactions that compete at the observed low symmetry magnetic skyrmion crystal wavevectors. Our findings underscore the potential of polar magnets with rich interaction schemes as promising for discovering new topological magnetic phases.
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Affiliation(s)
- Deepak Singh
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland.
| | - Yukako Fujishiro
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
| | - Satoru Hayami
- Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Samuel H Moody
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland
| | - Takuya Nomoto
- Research Center for Advanced Science and Technology, University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8904, Japan
| | - Priya R Baral
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland
| | - Victor Ukleev
- Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109, Berlin, Germany
| | - Robert Cubitt
- Institut-Laue-Langevin, 6 rue Jules Horowitz, Grenoble, 38000, France
| | | | - Dariusz J Gawryluk
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institut (PSI), CH-5232, Villigen PSI, Switzerland
| | - Ekaterina Pomjakushina
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institut (PSI), CH-5232, Villigen PSI, Switzerland
| | - Yoshichika Ōnuki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
| | - Ryotaro Arita
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
- Research Center for Advanced Science and Technology, University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8904, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Naoya Kanazawa
- Institute of Industrial Science, The University of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan
| | - Jonathan S White
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland.
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6
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Ueda H, Mankowsky R, Paris E, Sander M, Deng Y, Liu B, Leroy L, Nag A, Skoropata E, Wang C, Ukleev V, Perren GS, Dössegger J, Gurung S, Svetina C, Abreu E, Savoini M, Kimura T, Patthey L, Razzoli E, Lemke HT, Johnson SL, Staub U. Non-equilibrium dynamics of spin-lattice coupling. Nat Commun 2023; 14:7778. [PMID: 38012165 PMCID: PMC10681982 DOI: 10.1038/s41467-023-43581-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Accepted: 11/14/2023] [Indexed: 11/29/2023] Open
Abstract
Quantifying the dynamics of normal modes and how they interact with other excitations is of central importance in condensed matter. Spin-lattice coupling is relevant to several sub-fields of condensed matter physics; examples include spintronics, high-Tc superconductivity, and topological materials. However, experimental approaches that can directly measure it are rare and incomplete. Here we use time-resolved X-ray diffraction to directly access the ultrafast motion of atoms and spins following the coherent excitation of an electromagnon in a multiferroic hexaferrite. One striking outcome is the different phase shifts relative to the driving field of the two different components. This phase shift provides insight into the excitation process of such a coupled mode. This direct observation of combined lattice and magnetization dynamics paves the way to access the mode-selective spin-lattice coupling strength, which remains a missing fundamental parameter for ultrafast control of magnetism and is relevant to a wide variety of materials.
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Affiliation(s)
- Hiroki Ueda
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland.
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland.
| | - Roman Mankowsky
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Eugenio Paris
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Mathias Sander
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Yunpei Deng
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Biaolong Liu
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Ludmila Leroy
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Abhishek Nag
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Elizabeth Skoropata
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Chennan Wang
- Départment de Physique and Fribourg Center for Nanomaterials, Université de Fribourg, 1700, Fribourg, Switzerland
| | - Victor Ukleev
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489, Berlin, Germany
| | | | - Janine Dössegger
- Institute for Quantum Electronics, Physics Department, ETH Zurich, 8093, Zurich, Switzerland
| | - Sabina Gurung
- Institute for Quantum Electronics, Physics Department, ETH Zurich, 8093, Zurich, Switzerland
| | - Cristian Svetina
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
- Madrid Institute for Advanced Studies, IMDEA Nanociencia, Ciudad Universitaria de Cantoblanco, Calle Faraday 9, Madrid, 28049, Spain
| | - Elsa Abreu
- Institute for Quantum Electronics, Physics Department, ETH Zurich, 8093, Zurich, Switzerland
| | - Matteo Savoini
- Institute for Quantum Electronics, Physics Department, ETH Zurich, 8093, Zurich, Switzerland
| | - Tsuyoshi Kimura
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba, 277-8561, Japan
| | - Luc Patthey
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | - Elia Razzoli
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
| | | | - Steven Lee Johnson
- SwissFEL, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
- Institute for Quantum Electronics, Physics Department, ETH Zurich, 8093, Zurich, Switzerland
| | - Urs Staub
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland.
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7
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Karube K, Ukleev V, Kagawa F, Tokura Y, Taguchi Y, White JS. Unveiling the anisotropic fractal magnetic domain structure in bulk crystals of antiskyrmion host (Fe,Ni,Pd) 3P by small-angle neutron scattering. J Appl Crystallogr 2022. [DOI: 10.1107/s1600576722008561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Intermetallic Pd-doped (Fe,Ni)3P, which crystallizes in a non-centrosymmetric tetragonal structure with S
4 symmetry, has recently been discovered to host magnetic antiskyrmions, antivortex-like topological spin textures. In this material, uniaxial magnetic anisotropy and dipolar interactions play a significant role, giving rise to finely branched magnetic domain patterns near the surface of bulk crystals, as revealed by a previous magnetic force microscopy (MFM) measurement. However, small-angle neutron scattering (SANS) is a more suitable method for characterizing bulk properties and fractal structures on the mesoscopic length scale. In this study, using SANS and MFM, the magnetic domain structure in bulk single crystals of (Fe0.63Ni0.30Pd0.07)3P is quantitatively investigated. The SANS results demonstrate that the magnetic domain structure exhibits anisotropic fractal character on length scales down to the width of the magnetic domain walls. The fractal features are gradually lost in magnetic fields, and different field dependencies are observed at 300 and 2 K due to a temperature-dependent anisotropy. This study quantifies the fractality of the highly anisotropic magnetic domain structures in an antiskyrmion material, and highlights the versatility of SANS for the study of fractal structures in magnetic systems.
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8
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Ukleev V, Luo C, Abrudan R, Aqeel A, Back CH, Radu F. Chiral surface spin textures in Cu 2OSeO 3 unveiled by soft X-ray scattering in specular reflection geometry. Sci Technol Adv Mater 2022; 23:682-690. [PMID: 36277505 PMCID: PMC9586675 DOI: 10.1080/14686996.2022.2131466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 09/23/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
Resonant elastic soft X-ray magnetic scattering (XRMS) is a powerful tool to explore long-periodic spin textures in single crystals. However, due to the limited momentum transfer range imposed by long wavelengths of photons in the soft x-ray region, Bragg diffraction is restricted to crystals with the large lattice parameters. Alternatively, small-angle X-ray scattering has been involved in the soft energy X-ray range which, however, brings in difficulties with the sample preparation that involves focused ion beam milling to thin down the crystal to below a few hundred nm thickness. We show how to circumvent these restrictions using XRMS in specular reflection from a sub-nanometer smooth crystal surface. The method allows observing diffraction peaks from the helical and conical spin modulations at the surface of a Cu 2 OSeO 3 single crystal and probing their corresponding chirality as contributions to the dichroic scattered intensity. The results suggest a promising way to carry out XRMS studies on a plethora of noncentrosymmetric systems hitherto unexplored with soft X-rays due to the absence of the commensurate Bragg peaks in the available momentum transfer range.
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Affiliation(s)
- V. Ukleev
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - C. Luo
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
- Physik-Department, Technische Universität München, Garching, Germany
| | - R. Abrudan
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
| | - A. Aqeel
- Physik-Department, Technische Universität München, Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), München, Germany
| | - C. H. Back
- Physik-Department, Technische Universität München, Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), München, Germany
| | - F. Radu
- Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
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9
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White JS, Karube K, Ukleev V, Derlet PM, Cubitt R, Dewhurst CD, Wildes AR, Yu XZ, Rønnow HM, Tokura Y, Taguchi Y. Small-angle neutron scattering study of mesoscale magnetic disordering and skyrmion phase suppression in the frustrated chiral magnet Co 6.75Zn 6.75Mn 6.5. J Appl Crystallogr 2022; 55:1219-1231. [PMID: 36249507 PMCID: PMC9533762 DOI: 10.1107/s1600576722007403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 07/19/2022] [Indexed: 11/29/2022] Open
Abstract
In the frustrated chiral magnet Co6.75Zn6.75Mn6.5, small-angle neutron scattering reveals that the mesoscale chiral magnetism displays strong disorder and the skyrmion phase is nearly entirely suppressed. Co–Zn–Mn chiral cubic magnets display versatile magnetic skyrmion phases, including equilibrium phases stable far above and far below room temperature, and the facile creation of robust far-from-equilibrium skyrmion states. In this system, compositional disorder and magnetic frustration are key ingredients that have profound effects on the chiral magnetism. Reported here are studies of the magnetism in Co6.75Zn6.75Mn6.5 by magnetometry, small-angle neutron scattering (SANS), magnetic diffuse neutron scattering and Lorentz transmission electron microscopy (LTEM). While features in magnetometry and LTEM often give standard indications for skyrmion formation, they are not readily observed from the measurements on this system. Instead, skyrmion lattice correlations are only revealed by SANS, and they are found to form an orientationally disordered structure in a minority fraction of the sample. The majority fraction of the sample always displays orientationally disordered helical spin correlations, which undergo further disordering along the radial direction on cooling below the critical temperature (Tc ≃ 102 K). The near-complete suppression of the skyrmion phase, and the process of disordering on cooling, are attributed to competing magnetic interactions that dominate over the ferromagnetic interaction expected to favour chiral magnetism in this system. These competing interactions start to develop above Tc and become further enhanced towards low temperatures. The present observations of co-existing and disordered magnetic correlations over multiple length scales are not unique to Co6.75Zn6.75Mn6.5 but are seemingly common to the family of Co–Zn–Mn compounds with finite Mn, and their accurate description presents a challenge for theoretical modelling. In addition, this study highlights a need for neutron instrumentation capable of the comprehensive measurement of magnetic correlations over expanded ranges of momentum transfer in such multiple-length-scale magnets.
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10
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Takagi R, Matsuyama N, Ukleev V, Yu L, White JS, Francoual S, Mardegan JRL, Hayami S, Saito H, Kaneko K, Ohishi K, Ōnuki Y, Arima TH, Tokura Y, Nakajima T, Seki S. Square and rhombic lattices of magnetic skyrmions in a centrosymmetric binary compound. Nat Commun 2022; 13:1472. [PMID: 35354812 PMCID: PMC8967868 DOI: 10.1038/s41467-022-29131-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 03/01/2022] [Indexed: 11/29/2022] Open
Abstract
Magnetic skyrmions are topologically stable swirling spin textures with particle-like character, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems with Dzyaloshinskii-Moriya interaction, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds, such as Gd2PdSi3 and GdRu2Si2. For the latter systems, a distinct skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl4, by performing small-angle neutron and resonant elastic X-ray scattering experiments. Unlike previously reported centrosymmetric skyrmion-hosting materials, EuAl4 shows multiple-step reorientation of the fundamental magnetic modulation vector as a function of magnetic field, probably reflecting a delicate balance of associated itinerant-electron-mediated interactions. The present results demonstrate that a variety of distinctive skyrmion orders can be derived even in a simple centrosymmetric binary compound, which highlights rare-earth intermetallic systems as a promising platform to realize/control the competition of multiple topological magnetic phases in a single material. Typically, skyrmions appear in magnet systems which are non-centrosymmetric. Here, using neutron and X-ray scattering, Takagi et al show the emergence of a skyrmion phase in the centrosymmetric material EuAl4. This expands the range of materials potential hosting skyrmions.
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Affiliation(s)
- Rina Takagi
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan. .,Institute of Engineering Innovation, University of Tokyo, Tokyo, 113-0032, Japan. .,PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, 332-0012, Japan. .,RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.
| | - Naofumi Matsuyama
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
| | - Victor Ukleev
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), 5232, Villigen, Switzerland
| | - Le Yu
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), 5232, Villigen, Switzerland.,Laboratory for Ultrafast Microscopy and Electron Scattering (LUMES), Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland.,Laboratory of Nanoscale Magnetic Materials and Magnonics (LMGN), Institute of Materials, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Jonathan S White
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), 5232, Villigen, Switzerland
| | - Sonia Francoual
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607, Hamburg, Germany
| | - José R L Mardegan
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607, Hamburg, Germany
| | - Satoru Hayami
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan.,PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, 332-0012, Japan
| | - Hiraku Saito
- The Institute for Solid State Physics, University of Tokyo, Kashiwa, 277-8561, Japan
| | - Koji Kaneko
- Materials Sciences Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan.,J-PARC Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
| | - Kazuki Ohishi
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, 319-1106, Japan
| | - Yoshichika Ōnuki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.,Department of Advanced Materials Science, University of Tokyo, Kashiwa, 277-8561, Japan
| | - Yoshinori Tokura
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan.,RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.,Tokyo College, University of Tokyo, Tokyo, 113-8656, Japan
| | - Taro Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.,The Institute for Solid State Physics, University of Tokyo, Kashiwa, 277-8561, Japan
| | - Shinichiro Seki
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan.,Institute of Engineering Innovation, University of Tokyo, Tokyo, 113-0032, Japan.,PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, 332-0012, Japan.,RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
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11
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Ohtsuka Y, Kanazawa N, Hirayama M, Matsui A, Nomoto T, Arita R, Nakajima T, Hanashima T, Ukleev V, Aoki H, Mogi M, Fujiwara K, Tsukazaki A, Ichikawa M, Kawasaki M, Tokura Y. Emergence of spin-orbit coupled ferromagnetic surface state derived from Zak phase in a nonmagnetic insulator FeSi. Sci Adv 2021; 7:eabj0498. [PMID: 34788092 PMCID: PMC8598002 DOI: 10.1126/sciadv.abj0498] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 09/28/2021] [Indexed: 06/13/2023]
Abstract
FeSi is a nonmagnetic narrow-gap insulator, exhibiting peculiar charge and spin dynamics beyond a simple band structure picture. Those unusual features have been attracting renewed attention from topological aspects. Although the surface conduction was demonstrated according to size-dependent resistivity in bulk crystals, its topological characteristics and consequent electromagnetic responses remain elusive. Here, we demonstrate an inherent surface ferromagnetic-metal state of FeSi thin films and its strong spin-orbit coupling (SOC) properties through multiple characterizations of two-dimensional conductance, magnetization, and spintronic functionality. Terminated covalent bonding orbitals constitute the polar surface state with momentum-dependent spin textures due to Rashba-type spin splitting, as corroborated by unidirectional magnetoresistance measurements and first-principles calculations. As a consequence of the spin-momentum locking, nonequilibrium spin accumulation causes magnetization switching. These surface properties are closely related to the Zak phase of the bulk band topology. Our findings propose another route to explore noble metal–free materials for SOC-based spin manipulation.
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Affiliation(s)
- Yusuke Ohtsuka
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Naoya Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Motoaki Hirayama
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Akira Matsui
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Takuya Nomoto
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Ryotaro Arita
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Taro Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8561, Japan
| | | | - Victor Ukleev
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Hiroyuki Aoki
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tokai 319-1106, Japan
| | - Masataka Mogi
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Kohei Fujiwara
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Atsushi Tsukazaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Masakazu Ichikawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Masashi Kawasaki
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Yoshinori Tokura
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
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12
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Quan Y, Steiner J, Ukleev V, Kohlbrecher J, Vorobiev A, Hautle P. Impact of the neutron-depolarization effect on polarized neutron scattering in ferromagnets. IUCrJ 2021; 8:455-461. [PMID: 33953931 PMCID: PMC8086167 DOI: 10.1107/s2052252521003249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 03/26/2021] [Indexed: 06/12/2023]
Abstract
It has been known for decades that a ferromagnetic sample can depolarize a transmitted neutron beam. This effect was used and developed into the neutron-depolarization technique to investigate the magnetic structure of ferromagnetic materials. Since the polarization evolves continuously as the neutrons move through the sample, the initial spin states on scattering will be different at different depths within the sample. This leads to a contamination of the measured spin-dependent neutron-scattering intensities by the other spin-dependent cross sections. The effect has rarely been considered in polarized neutron-scattering experiments even though it has a crucial impact on the observable signal. A model is proposed to describe the depolarization of a neutron beam traversing a ferromagnetic sample, provide the procedure for data correction and give guidelines to choose the optimum sample thickness. It is experimentally verified for a small-angle neutron-scattering geometry with samples of the nanocristalline soft-magnet Vitroperm (Fe73Si16B7Nb3Cu1). The model is general enough to be adapted to other types of neutron-diffraction experiments and sample geometries.
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Affiliation(s)
- Yifan Quan
- Laboratory for Neutron and Muon Instrumentation, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Jakob Steiner
- Laboratory for Neutron and Muon Instrumentation, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Victor Ukleev
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Joachim Kohlbrecher
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland
| | - Alexei Vorobiev
- Department of Physics and Astronomy, Division of Materials Physics, Uppsala University, Uppsala, Sweden
| | - Patrick Hautle
- Laboratory for Neutron and Muon Instrumentation, Paul Scherrer Institute, 5232 Villigen, Switzerland
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13
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Swekis P, Sukhanov AS, Chen YC, Gloskovskii A, Fecher GH, Panagiotopoulos I, Sichelschmidt J, Ukleev V, Devishvili A, Vorobiev A, Inosov DS, Goennenwein STB, Felser C, Markou A. Magnetic and Electronic Properties of Weyl Semimetal Co 2MnGa Thin Films. Nanomaterials (Basel) 2021; 11:251. [PMID: 33477868 PMCID: PMC7832844 DOI: 10.3390/nano11010251] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 11/18/2022]
Abstract
Magnetic Weyl semimetals are newly discovered quantum materials with the potential for use in spintronic applications. Of particular interest is the cubic Heusler compound Co2MnGa due to its inherent magnetic and topological properties. This work presents the structural, magnetic and electronic properties of magnetron co-sputtered Co2MnGa thin films, with thicknesses ranging from 10 to 80 nm. Polarized neutron reflectometry confirmed a uniform magnetization through the films. Hard x-ray photoelectron spectroscopy revealed a high degree of spin polarization and localized (itinerant) character of the Mn d (Co d) valence electrons and accompanying magnetic moments. Further, broadband and field orientation-dependent ferromagnetic resonance measurements indicated a relation between the thickness-dependent structural and magnetic properties. The increase of the tensile strain-induced tetragonal distortion in the thinner films was reflected in an increase of the cubic anisotropy term and a decrease of the perpendicular uniaxial term. The lattice distortion led to a reduction of the Gilbert damping parameter and the thickness-dependent film quality affected the inhomogeneous linewidth broadening. These experimental findings will enrich the understanding of the electronic and magnetic properties of magnetic Weyl semimetal thin films.
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Affiliation(s)
- Peter Swekis
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
| | - Aleksandr S. Sukhanov
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
| | - Yi-Cheng Chen
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
- Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
| | | | - Gerhard H. Fecher
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
| | - Ioannis Panagiotopoulos
- Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece;
| | - Jörg Sichelschmidt
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
| | - Victor Ukleev
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, 5232 Villigen, Switzerland;
| | - Anton Devishvili
- Institut Laue Langevin, 38000 Grenoble, France;
- Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden;
| | - Alexei Vorobiev
- Department of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden;
| | - Dmytro S. Inosov
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
| | - Sebastian T. B. Goennenwein
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany; (D.S.I.); (S.T.B.G.)
- Center for Transport and Devices of Emergent Materials, Technische Universität Dresden, 01062 Dresden, Germany
- Department of Physics, University of Konstanz, 78457 Konstanz, Germany
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
| | - Anastasios Markou
- Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany; (P.S.); (A.S.S.); (Y.-C.C.); (G.H.F.); (J.S.); (C.F.)
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14
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Kanazawa N, Kitaori A, White JS, Ukleev V, Rønnow HM, Tsukazaki A, Ichikawa M, Kawasaki M, Tokura Y. Direct Observation of the Statics and Dynamics of Emergent Magnetic Monopoles in a Chiral Magnet. Phys Rev Lett 2020; 125:137202. [PMID: 33034489 DOI: 10.1103/physrevlett.125.137202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 08/24/2020] [Indexed: 06/11/2023]
Abstract
In the three-dimensional (3D) Heisenberg model, topological point defects known as spin hedgehogs behave as emergent magnetic monopoles, i.e., quantized sources and sinks of gauge fields that couple strongly to conduction electrons, and cause unconventional transport responses such as the gigantic Hall effect. We observe a dramatic change in the Hall effect upon the transformation of a spin hedgehog crystal in a chiral magnet MnGe through combined measurements of magnetotransport and small-angle neutron scattering (SANS). At low temperatures, well-defined SANS peaks and a negative Hall signal are each consistent with expectations for a static hedgehog lattice. In contrast, a positive Hall signal takes over when the hedgehog lattice fluctuates at higher temperatures, with a diffuse SANS signal observed upon decomposition of the hedgehog lattice. Our approach provides a simple way to both distinguish and disentangle the roles of static and dynamic emergent monopoles on the augmented Hall motion of conduction electrons.
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Affiliation(s)
- N Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - A Kitaori
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - J S White
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - V Ukleev
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - H M Rønnow
- Laboratory for Quantum Magnetism (LQM), Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - A Tsukazaki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - M Ichikawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - M Kawasaki
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Y Tokura
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
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15
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Puphal P, Pomjakushin V, Kanazawa N, Ukleev V, Gawryluk DJ, Ma J, Naamneh M, Plumb NC, Keller L, Cubitt R, Pomjakushina E, White JS. Topological Magnetic Phase in the Candidate Weyl Semimetal CeAlGe. Phys Rev Lett 2020; 124:017202. [PMID: 31976692 DOI: 10.1103/physrevlett.124.017202] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 11/01/2019] [Indexed: 06/10/2023]
Abstract
We report the discovery of topological magnetism in the candidate magnetic Weyl semimetal CeAlGe. Using neutron scattering we find this system to host several incommensurate, square-coordinated multi-k[over →] magnetic phases below T_{N}. The topological properties of a phase stable at intermediate magnetic fields parallel to the c axis are suggested by observation of a topological Hall effect. Our findings highlight CeAlGe as an exceptional system for exploiting the interplay between the nontrivial topologies of the magnetization in real space and Weyl nodes in momentum space.
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Affiliation(s)
- Pascal Puphal
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Vladimir Pomjakushin
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Naoya Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Victor Ukleev
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Dariusz J Gawryluk
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Junzhang Ma
- Swiss Light Source (SLS), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
| | - Muntaser Naamneh
- Swiss Light Source (SLS), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
| | - Nicholas C Plumb
- Swiss Light Source (SLS), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
| | - Lukas Keller
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Robert Cubitt
- Institut Laue-Langevin (ILL), 71 avenue des Martyrs, CS 20156, 38042 Grenoble cedex 9, France
| | - Ekaterina Pomjakushina
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Jonathan S White
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
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16
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Mogi M, Nakajima T, Ukleev V, Tsukazaki A, Yoshimi R, Kawamura M, Takahashi KS, Hanashima T, Kakurai K, Arima TH, Kawasaki M, Tokura Y. Large Anomalous Hall Effect in Topological Insulators with Proximitized Ferromagnetic Insulators. Phys Rev Lett 2019; 123:016804. [PMID: 31386415 DOI: 10.1103/physrevlett.123.016804] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 03/24/2019] [Indexed: 06/10/2023]
Abstract
We report a proximity-driven large anomalous Hall effect in all-telluride heterostructures consisting of the ferromagnetic insulator Cr_{2}Ge_{2}Te_{6} and topological insulator (Bi,Sb)_{2}Te_{3}. Despite small magnetization in the (Bi,Sb)_{2}Te_{3} layer, the anomalous Hall conductivity reaches a large value of 0.2e^{2}/h in accord with a ferromagnetic response of the Cr_{2}Ge_{2}Te_{6}. The results show that the exchange coupling between the surface state of the topological insulator and the proximitized Cr_{2}Ge_{2}Te_{6} layer is effective and strong enough to open the sizable exchange gap in the surface state.
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Affiliation(s)
- Masataka Mogi
- Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Taro Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Victor Ukleev
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232, Villigen, Switzerland
| | - Atsushi Tsukazaki
- Institute for Materials Research, Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Ryutaro Yoshimi
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Minoru Kawamura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Kei S Takahashi
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- PRESTO, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0075, Japan
| | - Takayasu Hanashima
- PRESTO, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0075, Japan
| | - Kazuhisa Kakurai
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Masashi Kawasaki
- Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Tokyo College, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
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17
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Kurumaji T, Nakajima T, Ukleev V, Feoktystov A, Arima TH, Kakurai K, Tokura Y. Néel-Type Skyrmion Lattice in the Tetragonal Polar Magnet VOSe_{2}O_{5}. Phys Rev Lett 2017; 119:237201. [PMID: 29286691 DOI: 10.1103/physrevlett.119.237201] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Indexed: 06/07/2023]
Abstract
The formation of the triangular Skyrmion lattice is found in a tetragonal polar magnet VOSe_{2}O_{5}. By magnetization and small-angle neutron scattering measurements on the single crystals, we identify a cycloidal spin state at zero field and a Néel-type Skyrmion-lattice phase under a magnetic field along the polar axis. Adjacent to this phase, another magnetic phase of an incommensurate spin texture is identified at lower temperatures, tentatively assigned to a square Skyrmion-lattice phase. These findings exemplify the versatile features of Néel-type Skyrmions in bulk materials, and provide a further opportunity to explore the physics of topological spin textures in polar magnets.
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Affiliation(s)
- Takashi Kurumaji
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Taro Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Victor Ukleev
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - Artem Feoktystov
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Garching 85748, Germany
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan
| | - Kazuhisa Kakurai
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- CROSS-Tokai, Research Center for Neutron Science and Technology, Tokai, Ibaraki 319-1106, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
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Vorobiev A, Khassanov A, Ukleev V, Snigireva I, Konovalov O. Substantial Difference in Ordering of 10, 15, and 20 nm Iron Oxide Nanoparticles on a Water Surface: In Situ Characterization by the Grazing Incidence X-ray Scattering. Langmuir 2015; 31:11639-11648. [PMID: 26399881 DOI: 10.1021/acs.langmuir.5b02644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In the present study, for the first time, a unique combination of in situ grazing incidence small-angle X-ray scattering and X-ray reflectivity, accompanied by the pressure-area isotherm analysis, Brewster angle microscopy, and ex situ scanning electron microscopy, was applied for investigation of two-dimensional superlattices of magnetic nanoparticles as they form on a water surface in a Langmuir trough. Iron oxide particles of different sizes stabilized with a single layer of oleic acid were used. It is demonstrated that monodisperse 10 nm particles on a water surface reproducibly form identical highly ordered monolayers in a wide range of experimental conditions, while monodisperse 20 nm particles always form compact three-dimensional clusters and never the monolayers. Monodisperse particles of an intermediate size, 15 nm in diameter, build a metastable monolayer, which shows a tendency for spontaneous transformation to bi-, tri-, and multilayer islands. The importance to use both grazing incidence small-angle X-ray scattering and X-ray reflectivity together with the complementary techniques, to avoid misinterpretation of separate experimental data sets, is underlined.
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Affiliation(s)
- A Vorobiev
- Department of Physics and Astronomy, Uppsala University , Box 516, 751 20 Uppsala, Sweden
- European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France
| | - A Khassanov
- European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France
- Organic Materials and Devices, Friedrich-Alexander-Universität Erlangen-Nürnberg , Martensstraße 7, 91058 Erlangen, Germany
| | - V Ukleev
- Department of Physics and Astronomy, Uppsala University , Box 516, 751 20 Uppsala, Sweden
- Petersburg Nuclear Physics Institute , Orlova Roscha, Gatchina, St. Petersburg 188300, Russia
| | - I Snigireva
- European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France
| | - O Konovalov
- European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France
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