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Mondal AK, Mukhopadhyay S, Heinig P, Salikhov R, Hellwig O, Barman A. Femtosecond Laser-Induced Transient Magnetization Enhancement and Ultrafast Demagnetization Mediated by Domain Wall Origami. ACS NANO 2024. [PMID: 38905311 DOI: 10.1021/acsnano.4c02910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/23/2024]
Abstract
Femtosecond laser-induced ultrafast magnetization dynamics are all-optically probed for different remanent magnetic domain states of a [Co/Pt]22 multilayer sample, thus revealing the tunability of the direct transport of spin angular momentum across domain walls. A variety of different magnetic domain configurations (domain wall origami) at remanence achieved by applying different magnetic field histories are investigated by time-resolved magneto-optical Kerr effect magnetometry to probe the ultrafast magnetization dynamics. Depending on the underlying domain landscape, the spin-transport-driven magnetization dynamics show a transition from typical ultrafast demagnetization to being fully dominated by an anomalous transient magnetization enhancement (TME) via a state in which both TME and demagnetization coexist in the system. Thereby, the study reveals an extrinsic channel for the modulation of spin transport, which introduces a route for the development of magnetic spin-texture-driven ultrafast spintronic devices.
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Affiliation(s)
- Amrit Kumar Mondal
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
- Technical Research Centre, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
| | - Suchetana Mukhopadhyay
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
- Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741252, India
| | - Peter Heinig
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
- Institute of Physics, Chemnitz University of Technology, Reichenhainer Strasse 70, 09107 Chemnitz, Germany
| | - Ruslan Salikhov
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Olav Hellwig
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
- Institute of Physics, Chemnitz University of Technology, Reichenhainer Strasse 70, 09107 Chemnitz, Germany
| | - Anjan Barman
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
- Technical Research Centre, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700106, India
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2
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Lu X, Lin Z, Pi H, Zhang T, Li G, Gong Y, Yan Y, Ruan X, Li Y, Zhang H, Li L, He L, Wu J, Zhang R, Weng H, Zeng C, Xu Y. Ultrafast magnetization enhancement via the dynamic spin-filter effect of type-II Weyl nodes in a kagome ferromagnet. Nat Commun 2024; 15:2410. [PMID: 38499551 PMCID: PMC10948858 DOI: 10.1038/s41467-024-46604-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 02/21/2024] [Indexed: 03/20/2024] Open
Abstract
The magnetic type-II Weyl semimetal (MWSM) Co3Sn2S2 has recently been found to host a variety of remarkable phenomena including surface Fermi-arcs, giant anomalous Hall effect, and negative flat band magnetism. However, the dynamic magnetic properties remain relatively unexplored. Here, we investigate the ultrafast spin dynamics of Co3Sn2S2 crystal using time-resolved magneto-optical Kerr effect and reflectivity spectroscopies. We observe a transient magnetization behavior, consisting of spin-flipping dominated fast demagnetization, slow demagnetization due to overall half-metallic electronic structures, and an unexpected ultrafast magnetization enhancement lasting hundreds of picoseconds upon femtosecond laser excitation. By combining temperature-, pump fluence-, and pump polarization-dependent measurements, we unambiguously demonstrate the correlation between the ultrafast magnetization enhancement and the Weyl nodes. Our theoretical modelling suggests that the excited electrons are spin-polarized when relaxing, leading to the enhanced spin-up density of states near the Fermi level and the consequently unusual magnetization enhancement. Our results reveal the unique role of the Weyl properties of Co3Sn2S2 in femtosecond laser-induced spin dynamics.
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Affiliation(s)
- Xianyang Lu
- School of Integrated Circuits, Nanjing University, Suzhou, 215163, China
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Zhiyong Lin
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Hanqi Pi
- Beijing National Research Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
- School of Physical Science, University of Chinese Academy of Sciences, Beijing, 100049, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Tan Zhang
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA, 19104-6323, USA
| | - Guanqi Li
- School of Integrated Circuits, Guangdong University of Technology, Guangzhou, 510006, China
| | - Yuting Gong
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Yu Yan
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Xuezhong Ruan
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Yao Li
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Hui Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Lin Li
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Liang He
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Jing Wu
- School of Integrated Circuits, Guangdong University of Technology, Guangzhou, 510006, China.
- York-Nanjing International Joint Center in Spintronics, School of Physics, Engineering and Technology, University of York, York, YO10 5DD, UK.
| | - Rong Zhang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China
| | - Hongming Weng
- Beijing National Research Center for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
- School of Physical Science, University of Chinese Academy of Sciences, Beijing, 100049, China.
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
| | - Changgan Zeng
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
- CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.
| | - Yongbing Xu
- School of Integrated Circuits, Nanjing University, Suzhou, 215163, China.
- State Key Laboratory of Spintronics Devices and Technologies, Nanjing University, Suzhou, 215163, China.
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, China.
- York-Nanjing International Joint Center in Spintronics, School of Physics, Engineering and Technology, University of York, York, YO10 5DD, UK.
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3
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Ryan SA, Johnsen PC, Elhanoty MF, Grafov A, Li N, Delin A, Markou A, Lesne E, Felser C, Eriksson O, Kapteyn HC, Grånäs O, Murnane MM. Optically controlling the competition between spin flips and intersite spin transfer in a Heusler half-metal on sub-100-fs time scales. SCIENCE ADVANCES 2023; 9:eadi1428. [PMID: 37948525 PMCID: PMC10637748 DOI: 10.1126/sciadv.adi1428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 10/12/2023] [Indexed: 11/12/2023]
Abstract
The direct manipulation of spins via light may provide a path toward ultrafast energy-efficient devices. However, distinguishing the microscopic processes that can occur during ultrafast laser excitation in magnetic alloys is challenging. Here, we study the Heusler compound Co2MnGa, a material that exhibits very strong light-induced spin transfers across the entire M-edge. By combining the element specificity of extreme ultraviolet high-harmonic probes with time-dependent density functional theory, we disentangle the competition between three ultrafast light-induced processes that occur in Co2MnGa: same-site Co-Co spin transfer, intersite Co-Mn spin transfer, and ultrafast spin flips mediated by spin-orbit coupling. By measuring the dynamic magnetic asymmetry across the entire M-edges of the two magnetic sublattices involved, we uncover the relative dominance of these processes at different probe energy regions and times during the laser pulse. Our combined approach enables a comprehensive microscopic interpretation of laser-induced magnetization dynamics on time scales shorter than 100 femtoseconds.
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Affiliation(s)
- Sinéad A. Ryan
- JILA, University of Colorado Boulder, 440 UCB, Boulder, CO 80309, USA
| | - Peter C. Johnsen
- JILA, University of Colorado Boulder, 440 UCB, Boulder, CO 80309, USA
| | - Mohamed F. Elhanoty
- Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box-516, SE 75120, Sweden
| | - Anya Grafov
- JILA, University of Colorado Boulder, 440 UCB, Boulder, CO 80309, USA
| | - Na Li
- JILA, University of Colorado Boulder, 440 UCB, Boulder, CO 80309, USA
| | - Anna Delin
- Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, AlbaNova University Center, SE-10691 Stockholm, Sweden
- Swedish e-Science Research Center (SeRC), KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
- Wallenberg Initiative Materials Science for Sustainability, Uppsala University, 75121 Uppsala, Sweden
| | - Anastasios Markou
- Physics Department, University of Ioannina, 45110 Ioannina, Greece
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Edouard Lesne
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Olle Eriksson
- Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box-516, SE 75120, Sweden
- Wallenberg Initiative Materials Science for Sustainability, Uppsala University, 75121 Uppsala, Sweden
| | - Henry C. Kapteyn
- JILA, University of Colorado Boulder, 440 UCB, Boulder, CO 80309, USA
- KMLabs Inc., Boulder, CO 80301, USA
| | - Oscar Grånäs
- Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box-516, SE 75120, Sweden
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4
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Orfila G, Sanchez-Manzano D, Arora A, Cuellar F, Ruiz-Gómez S, Rodriguez-Corvillo S, López S, Peralta A, Carreira SJ, Gallego F, Tornos J, Rouco V, Riquelme JJ, Munuera C, Mompean FJ, Garcia-Hernandez M, Sefrioui Z, Villegas JE, Perez L, Rivera-Calzada A, Leon C, Valencia S, Santamaria J. Large Magnetoresistance of Isolated Domain Walls in La 2/3 Sr 1/3 MnO 3 Nanowires. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2211176. [PMID: 37046341 DOI: 10.1002/adma.202211176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 03/13/2023] [Indexed: 06/19/2023]
Abstract
Generation, manipulation, and sensing of magnetic domain walls are cornerstones in the design of efficient spintronic devices. Half-metals are amenable for this purpose as large low field magnetoresistance signals can be expected from spin accumulation at spin textures. Among half metals, La1- x Srx MnO3 (LSMO) manganites are considered as promising candidates for their robust half-metallic ground state, Curie temperature above room temperature (Tc = 360 K, for x = 1/3), and chemical stability. Yet domain wall magnetoresistance is poorly understood, with large discrepancies in the reported values and conflicting interpretation of experimental data due to the entanglement of various source of magnetoresistance, namely, spin accumulation, anisotropic magnetoresistance, and colossal magnetoresistance. In this work, the domain wall magnetoresistance is measured in LSMO cross-shape nanowires with single-domain walls nucleated across the current path. Magnetoresistance values above 10% are found to be originating at the spin accumulation caused by the mistracking effect of the spin texture of the domain wall by the conduction electrons. Fundamentally, this result shows the importance on non-adiabatic processes at spin textures despite the strong Hund coupling to the localized t2g electrons of the manganite. These large magnetoresistance values are high enough for encoding and reading magnetic bits in future oxide spintronic sensors.
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Affiliation(s)
- Gloria Orfila
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | | | - Ashima Arora
- Department Spin and Topology in Quantum Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, 12489, Berlin, Germany
| | - Fabian Cuellar
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | - Sandra Ruiz-Gómez
- Physics of Quantum Materials, Max Planck Institute for Chemical Physics of Solids, 01187, Dresden, Germany
| | - Sara Rodriguez-Corvillo
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | - Sandra López
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | - Andrea Peralta
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | | | - Fernando Gallego
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | - Javier Tornos
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | - Victor Rouco
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
| | - Juan J Riquelme
- Departamento de Sistemas con baja dimensionalidad, Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, 28049, Cantoblanco, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
| | - Carmen Munuera
- Departamento de Sistemas con baja dimensionalidad, Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, 28049, Cantoblanco, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
| | - Federico J Mompean
- Departamento de Sistemas con baja dimensionalidad, Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, 28049, Cantoblanco, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
| | - Mar Garcia-Hernandez
- Departamento de Sistemas con baja dimensionalidad, Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, 28049, Cantoblanco, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
| | - Zouhair Sefrioui
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
| | | | - Lucas Perez
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
- Instituto Madrileño de Estudios Avanzados - IMDEA Nanoscience, 28049, Madrid, Spain
| | - Alberto Rivera-Calzada
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
| | - Carlos Leon
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
| | - Sergio Valencia
- Department Spin and Topology in Quantum Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, 12489, Berlin, Germany
| | - Jacobo Santamaria
- GFMC, Department Física de Materiales, Facultad de Física, Universidad Complutense, Madrid, 28040, Spain
- Unidad Asociada UCM/CSIC, Laboratorio de Heteroestructuras con aplicación en spintrónica, 28140, Madrid, Spain
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Jiang T, Zhao X, Chen Z, You Y, Lai T, Zhao J. Ultrafast Dynamics of Demagnetization in FeMn/MnGa Bilayer Nanofilm Structures via Phonon Transport. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:nano12224088. [PMID: 36432373 PMCID: PMC9698983 DOI: 10.3390/nano12224088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 11/17/2022] [Accepted: 11/18/2022] [Indexed: 06/04/2023]
Abstract
Superdiffusive spin transport has been proposed as a new mechanism of ultrafast demagnetization in layered magnetic nanostructures and demonstrated experimentally. However, it is unknown if it is possible for phonon transport to occur and manipulate ultrafast demagnetization. Here, we explore the ultrafast dynamics of demagnetization of an antiferromagnet/ferromagnet bilayer nanostructure, of a FeMn/MnGa bilayer film prepared by molecular beam epitaxy. Ultrafast dynamics of a two-step demagnetization were observed through the time-resolved magneto-optical Kerr effect. The first-step fast component of the two-step demagnetization occurred within ~200 fs, while the second-step slow component emerged in a few tens of picoseconds. For a single MnGa film, only the ultrafast dynamics of the first-step fast demagnetization were observed, revealing that the second-step slow demagnetization originates from interlayer phonon transport. A four-temperature model considering phonon transport was developed and used to effectively reproduce the observed ultrafast dynamics of two-step demagnetization. Our results reveal the effect of phonon transport on demagnetization for the first time and open up a new route to manipulate ultrafast demagnetization in layered magnetic structures.
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Affiliation(s)
- Tianran Jiang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xupeng Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
| | - Zhifeng Chen
- School of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006, China
| | - Yongyong You
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Tianshu Lai
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Jianhua Zhao
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
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6
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Yang Y. Mini-review of interesting properties in Mn2CoAl bulk and films. Front Chem 2022; 10:1054337. [PMID: 36339051 PMCID: PMC9626756 DOI: 10.3389/fchem.2022.1054337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 10/06/2022] [Indexed: 12/05/2022] Open
Abstract
Heusler compounds exhibit many interesting properties, such as high thermopower, magnetocaloric properties, and even topological insulator states. Heusler Mn2CoAl alloy has been experimentally and theoretically proposed as a promising spin-gapless semiconductor with novel electronic, magnetic, spintronic, transport, and topological properties. Furthermore, the spin-gapless semiconducting-like behaviors are also predicted in Mn2CoAl films by measuring the transport and magnetic properties. This mini-review systematically summarizes the interesting properties of Mn2CoAl bulk and Mn2CoAl-based films. This mini-review is hoped to guide further experimental investigations and applications in the particular scientific community.
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7
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Garcia JM, Sayres SG. Tuning the photodynamics of sub-nanometer neutral chromium oxide clusters through sequential oxidation. NANOSCALE 2022; 14:7798-7806. [PMID: 35535667 DOI: 10.1039/d2nr00464j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Sub-nanometer neutral chromium oxide clusters were produced in the gas phase through laser ablation and their low-lying excited state lifetimes were measured using femtosecond pump-probe spectroscopy. Time-dependent density functional theory calculations relate the trends in experimental lifetimes to the cluster's electronic structure. The photoexcited (CrO2)n (n < 5) cluster transients with the absence of up to four O atoms (CrnO2n-x, x < 5) exhibit a ∼30 fs and sub-ps lifetime, attributed to instantaneous metallic e-e scattering and vibrationally mediated charge carrier relaxation, respectively. A long-lived (>2 ps) response is found in both small and clusters with low O content, indicating that terminal CrO bonds facilitate efficient excited state relaxation. The ∼30 fs transient signal fraction grows nearly linearly with oxidation, matching the amount of O-2p to Cr-3d charge transfer character of the photoexcitation and suggesting a gradual transition between semiconducting and metallic behavior in chromium oxide clusters at the molecular level. The results presented herein suggest that the photocatalytic properties of chromium oxides can be tunable based on size and oxidation.
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Affiliation(s)
- Jacob M Garcia
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA.
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ 85287, USA
| | - Scott G Sayres
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA.
- Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ 85287, USA
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8
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Garcia JM, Sayres SG. Increased Excited State Metallicity in Neutral Cr 2O n Clusters ( n < 5) upon Sequential Oxidation. J Am Chem Soc 2021; 143:15572-15575. [PMID: 34516101 DOI: 10.1021/jacs.1c07275] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Excited state lifetimes of neutral Cr2On (n < 5) clusters were measured using femtosecond pump-probe spectroscopy. Density functional theory calculations reveal that the excited state dynamics are correlated with changes in the cluster's electronic structure with increasing oxidation. Upon absorption of a UV (400 nm) photon, the clusters exhibit features attributed to three separate relaxation processes. All clusters exhibit similar subpicosecond lifetimes, attributed to vibrational relaxation. However, the ∼30 fs transient signal fraction grows linearly with oxidation, matching the amount of O to Cr charge transfer character of the photoexcitation and highlighting a gradual transition between semiconducting and metallic behavior at the molecular level. A long-lived (>2.5 ps) response is recorded only in clusters with significant d-electron character, suggesting that adiabatic relaxation back to the ground state is efficient in heavily oxidized clusters, due to the presence of terminal O atoms. The simple picture of sequential oxidation of Cr2On reveals a linear variation in the contributions of each relaxation component to the total transient signals, therefore opening possibilities for the design of new molecular spintronic materials.
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Affiliation(s)
- Jacob M Garcia
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States.,Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona 85287, United States
| | - Scott G Sayres
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States.,Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, Arizona 85287, United States
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9
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Faiza-Rubab S, Naseem S, Alay-E-Abbas SM, Zulfiqar M, Zhao Y, Nazir S. Structural stability and evolution of half-metallicity in Ba 2CaMoO 6: interplay of hole- and electron-doping. Phys Chem Chem Phys 2021; 23:19472-19481. [PMID: 34524322 DOI: 10.1039/d1cp03247j] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Half-metallic ferromagnetic materials have attracted a lot of attention due to their probable technological applications in spintronics. In this respect, doping plays a crucial role in tailoring or controlling the physical properties of the system. Herein, the impact of both hole and electron doping on the structural, electronic and magnetic properties of the recent high pressure synthesized non-magnetic insulator Ba2CaMoO6 double perovskite oxide are investigated by replacing one of the Mo ions with Nb and Tc. The structural and mechanical stability of the undoped/doped materials are analyzed by calculating the formation energies and stiffness tensors, respectively, which confirm the system's stability. Interestingly, our results revealed that Nb- and Tc-doped systems display an electronic transition from insulating to p- and n-type half-metallic ferromagnetic states, respectively. The most striking feature of the present study is that oxygen ions become spin-polarized, with a magnetic moment of ∼0.12 μB per atom, and are mainly responsible for conductivity in the Nb-doped system. However, the admixture of Tc 4d non-degenerate orbitals are primarily contributing to the metallicity in the Tc-doped structure, with a moment of ∼0.59 μB. It is also found that Nb and Tc ions remain in the 5+ and 7+ states with electronic configurations of t22g↑t22g↓e0g↑e0g↓ and t32g↑t22g↓e0g↑e0g↓, with spin states of S = 0 and S = 1/2 in the individual doped systems, respectively. Hence, the present work proposes that a doping strategy with a suitable candidate could be beneficial to tune the physical properties of the materials for their potential utilization in advanced spin-based devices.
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Affiliation(s)
- S Faiza-Rubab
- Department of Physics, University of Sargodha, Sargodha, 40100, Pakistan.
| | - Shahnila Naseem
- Department of Physics, University of Sargodha, Sargodha, 40100, Pakistan.
| | - Syed Muhammad Alay-E-Abbas
- Applied Physics, Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, 97187 Luleå, Sweden.,Computational Materials Modeling Laboratory, Department of Physics, Government College University, Faisalabad, 38040, Faisalabad, Pakistan
| | - M Zulfiqar
- Department of Physics, University of Sargodha, Sargodha, 40100, Pakistan.
| | - Y Zhao
- Department of Physics, Yantai University, Yantai, 264005, People's Republic of China
| | - S Nazir
- Department of Physics, University of Sargodha, Sargodha, 40100, Pakistan.
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10
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Nazir S. Insulator-to-half metal transition and enhancement of structural distortions in [Formula: see text] double perovskite oxide via hole-doping. Sci Rep 2021; 11:1240. [PMID: 33441783 PMCID: PMC7806915 DOI: 10.1038/s41598-020-80265-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 12/18/2020] [Indexed: 11/09/2022] Open
Abstract
Using density functional theory calculations, we found that recently high-pressure synthesized double perovskite oxide [Formula: see text] exhibits ferrimagnetic (FiM) Mott-insulating state having an energy band gap of 0.20 eV which confirms the experimental observations (Feng et al. in Inorg Chem 58:397-404, 2019). Strong antiferromagnetic superexchange interactions between high-energy half-filled [Formula: see text]-[Formula: see text] and low-energy partially filled [Formula: see text] orbitals, results in a FiM spin ordering. Besides, the effect of 3d transition metal (TM = Cr, Mn, and Fe) doping with 50% concentration at Ni sites on its electronic and magnetic properties is explored. It is established that smaller size cation-doping at the B site enhances the structural distortion, which further gives strength to the FiM ordering temperature. Interestingly, our results revealed that all TM-doped structures exhibit an electronic transition from Mott-insulating to a half-metallic state with effective integral spin moments. The admixture of Ir 5d orbitals in the spin-majority channel are mainly responsible for conductivity, while the spin minority channel remains an insulator. Surprisingly, a substantial reduction and enhancement of spin moment are found on non-equivalent Ir and oxygen ions, respectively. This leads the Ir ion in a mixed-valence state of [Formula: see text] and [Formula: see text] in all doped systems having configurations of [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]), respectively. Hence, the present work proposes that doping engineering with suitable impurity elements could be an effective way to tailor the physical properties of the materials for their technological potential utilization in advanced spin devices.
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Affiliation(s)
- Safdar Nazir
- Department of Physics, University of Sargodha, Sargodha, 40100 Pakistan
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11
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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.
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Affiliation(s)
- A Eschenlohr
- Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany
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12
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Guillemard C, Zhang W, Malinowski G, de Melo C, Gorchon J, Petit-Watelot S, Ghanbaja J, Mangin S, Le Fèvre P, Bertran F, Andrieu S. Engineering Co 2 MnAl x Si 1- x Heusler Compounds as a Model System to Correlate Spin Polarization, Intrinsic Gilbert Damping, and Ultrafast Demagnetization. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e1908357. [PMID: 32452576 DOI: 10.1002/adma.201908357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 04/07/2020] [Accepted: 04/14/2020] [Indexed: 06/11/2023]
Abstract
Engineering of magnetic materials for developing better spintronic applications relies on the control of two key parameters: the spin polarization and the Gilbert damping, responsible for the spin angular momentum dissipation. Both of them are expected to affect the ultrafast magnetization dynamics occurring on the femtosecond timescale. Here, engineered Co2 MnAlx Si1- x Heusler compounds are used to adjust the degree of spin polarization at the Fermi energy, P, from 60% to 100% and to investigate how they correlate with the damping. It is experimentally demonstrated that the damping decreases when increasing the spin polarization from 1.1 × 10-3 for Co2 MnAl with 63% spin polarization to an ultralow value of 4.6 × 10-4 for the half-metallic ferromagnet Co2 MnSi. This allows the investigation of the relation between these two parameters and the ultrafast demagnetization time characterizing the loss of magnetization occurring after femtosecond laser pulse excitation. The demagnetization time is observed to be inversely proportional to 1 - P and, as a consequence, to the magnetic damping, which can be attributed to the similarity of the spin angular momentum dissipation processes responsible for these two effects. Altogether, the high-quality Heusler compounds allow control over the band structure and therefore the channel for spin angular momentum dissipation.
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Affiliation(s)
- Charles Guillemard
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
- Synchrotron SOLEIL-CNRS, Saint-Aubin, Gif-sur-Yvette, 91192, France
| | - Wei Zhang
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
| | - Gregory Malinowski
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
| | - Claudia de Melo
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
| | - Jon Gorchon
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
| | | | - Jaafar Ghanbaja
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
| | - Stéphane Mangin
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
| | - Patrick Le Fèvre
- Synchrotron SOLEIL-CNRS, Saint-Aubin, Gif-sur-Yvette, 91192, France
| | - Francois Bertran
- Synchrotron SOLEIL-CNRS, Saint-Aubin, Gif-sur-Yvette, 91192, France
| | - Stéphane Andrieu
- Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, 54500, France
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13
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Tengdin P, Gentry C, Blonsky A, Zusin D, Gerrity M, Hellbrück L, Hofherr M, Shaw J, Kvashnin Y, Delczeg-Czirjak EK, Arora M, Nembach H, Silva TJ, Mathias S, Aeschlimann M, Kapteyn HC, Thonig D, Koumpouras K, Eriksson O, Murnane MM. Direct light-induced spin transfer between different elements in a spintronic Heusler material via femtosecond laser excitation. SCIENCE ADVANCES 2020; 6:eaaz1100. [PMID: 32010777 PMCID: PMC6968936 DOI: 10.1126/sciadv.aaz1100] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 11/26/2019] [Indexed: 05/23/2023]
Abstract
Heusler compounds are exciting materials for future spintronics applications because they display a wide range of tunable electronic and magnetic interactions. Here, we use a femtosecond laser to directly transfer spin polarization from one element to another in a half-metallic Heusler material, Co2MnGe. This spin transfer initiates as soon as light is incident on the material, demonstrating spatial transfer of angular momentum between neighboring atomic sites on time scales < 10 fs. Using ultrafast high harmonic pulses to simultaneously and independently probe the magnetic state of two elements during laser excitation, we find that the magnetization of Co is enhanced, while that of Mn rapidly quenches. Density functional theory calculations show that the optical excitation directly transfers spin from one magnetic sublattice to another through preferred spin-polarized excitation pathways. This direct manipulation of spins via light provides a path toward spintronic devices that can operate on few-femtosecond or faster time scales.
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Affiliation(s)
- Phoebe Tengdin
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - Christian Gentry
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - Adam Blonsky
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - Dmitriy Zusin
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - Michael Gerrity
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - Lukas Hellbrück
- Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - Moritz Hofherr
- Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - Justin Shaw
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - Yaroslav Kvashnin
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
| | | | - Monika Arora
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - Hans 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
| | - Tom J. Silva
- Quantum Electromagnetics Division, National Institute of Standards and Technology, Boulder, CO 80305, USA
| | - Stefan Mathias
- Georg-August-Universität Göttingen, I. Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Martin Aeschlimann
- Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schroedinger Strasse 46, 67663 Kaiserslautern, Germany
| | - Henry C. Kapteyn
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
| | - Danny Thonig
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
- School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
| | | | - Olle Eriksson
- Department of Physics and Astronomy, University Uppsala, S-75120 Uppsala, Sweden
- School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden
| | - Margaret M. Murnane
- Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA
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14
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Bhandari SR, Yadav DK, Belbase BP, Zeeshan M, Sadhukhan B, Rai DP, Thapa RK, Kaphle GC, Ghimire MP. Electronic, magnetic, optical and thermoelectric properties of Ca2Cr1−xNixOsO6 double perovskites. RSC Adv 2020; 10:16179-16186. [PMID: 35516814 PMCID: PMC9059137 DOI: 10.1039/c9ra10775d] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 04/07/2020] [Indexed: 12/17/2022] Open
Abstract
With the help of density functional theory calculations, we explored the recently synthesized double perovskite material Ca2CrOsO6 and found it to be a ferrimagnetic insulator with a band gap of ∼0.6 eV.
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Affiliation(s)
- Shalika R. Bhandari
- Central Department of Physics
- Tribhuvan University
- Kathmandu
- Nepal
- Institute for Theoretical Solid State Physics
| | - D. K. Yadav
- Condensed Matter Physics Research Center (CMPRC)
- Butwal
- Nepal
| | - B. P. Belbase
- Central Department of Physics
- Tribhuvan University
- Kathmandu
- Nepal
- Condensed Matter Physics Research Center (CMPRC)
| | - M. Zeeshan
- Department of Chemistry
- Indian Institute of Technology Roorkee
- Roorkee 247667
- India
| | - B. Sadhukhan
- Institute for Theoretical Solid State Physics
- IFW Dresden e. V
- Dresden-01069
- Germany
| | - D. P. Rai
- Physical Sciences Research Center (PSRC)
- Department of Physics
- Pachhunga University College
- Aizawl
- India
| | - R. K. Thapa
- Condensed Matter Physics Research Center (CMPRC)
- Butwal
- Nepal
| | - G. C. Kaphle
- Central Department of Physics
- Tribhuvan University
- Kathmandu
- Nepal
- Condensed Matter Physics Research Center (CMPRC)
| | - Madhav Prasad Ghimire
- Central Department of Physics
- Tribhuvan University
- Kathmandu
- Nepal
- Institute for Theoretical Solid State Physics
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15
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Yousefi Sarraf S, Singh S, Garcia-Castro AC, Trappen R, Mottaghi N, Cabrera GB, Huang CY, Kumari S, Bhandari G, Bristow AD, Romero AH, Holcomb MB. Surface Recombination in Ultra-Fast Carrier Dynamics of Perovskite Oxide La 0.7Sr 0.3MnO 3 Thin Films. ACS NANO 2019; 13:3457-3465. [PMID: 30807694 DOI: 10.1021/acsnano.8b09595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Aspects of the optoelectronic performance of thin-film ferromagnetic materials are evaluated for application in ultrafast devices. Dynamics of photocarriers and their associated spin polarization are measured using transient reflectivity (TR) measurements in cross linear and circular polarization configurations for La0.7Sr0.3MnO3 films with a range of thicknesses. Three spin-related recombination mechanisms have been observed for thicker films (thickness of d ≥ 20 nm) at different time regimes (τ), which are attributed to the electron-phonon recombination (τ < 1 ps), phonon-assisted spin-lattice recombination (τ ∼ 100 ps), and thermal diffusion and radiative recombination (τ > 1 ns). Density functional theory (DFT+U) based first-principles calculations provide information about the nature of the optical transitions and their probabilities for the majority and the minority spin channels. These transitions are partly responsible for the aforementioned recombination mechanisms, identified through the comparison of linear and circular TR measurements. The same sets of measurements for thinner films (4.4 nm ≤ d < 20 nm) revealed an additional relaxation dynamic (τ ∼ 10 ps), which is attributed to the enhanced surface recombination of charge carriers. Our DFT+U calculations further corroborate this observation, indicating an increase in the surface density of states with decreasing film thickness which results in higher amplitude and smaller time constant for surface recombination as the film thickness decreases.
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Affiliation(s)
- Saeed Yousefi Sarraf
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Sobhit Singh
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
- Department of Physics and Astronomy , Rutgers University , Piscataway , New Jersey 08854-8019 , United States
| | | | - Robbyn Trappen
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Navid Mottaghi
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Guerau B Cabrera
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Chih-Yeh Huang
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
- Department Mechanical and Aerospace Engineering , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Shalini Kumari
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Ghadendra Bhandari
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Alan D Bristow
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Aldo H Romero
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
| | - Mikel B Holcomb
- Department of Physics and Astronomy , West Virginia University , Morgantown , West Virginia 26501-6315 , United States
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16
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Liu B, Niu W, Chen Y, Ruan X, Tang Z, Wang X, Liu W, He L, Li Y, Wu J, Tang S, Du J, Zhang R, Xu Y. Ultrafast Orbital-Oriented Control of Magnetization in Half-Metallic La 0.7 Sr 0.3 MnO 3 Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1806443. [PMID: 30663164 DOI: 10.1002/adma.201806443] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 12/15/2018] [Indexed: 06/09/2023]
Abstract
Manipulating spins by ultrafast pulse laser provides a new avenue to switch the magnetization for spintronic applications. While the spin-orbit coupling is known to play a pivotal role in the ultrafast laser-induced demagnetization, the effect of the anisotropic spin-orbit coupling on the transient magnetization remains an open issue. This study uncovers the role of anisotropic spin-orbit coupling in the spin dynamics in a half-metallic La0.7 Sr0.3 MnO3 film by ultrafast pump-probe technique. The magnetic order is found to be transiently enhanced or attenuated within the initial sub-picosecond when the probe light is tuned to be s- or p-polarized, respectively. The subsequent slow demagnetization amplitude follows the fourfold symmetry of the d x 2 - y 2 orbitals as a function of the polarization angles of the probe light. A model based on the Elliott-Yafet spin-flip scatterings is proposed to reveal that the transient magnetization enhancement is related to the spin-mixed states arising from the anisotropic spin-orbit coupling. The findings provide new insights into the spin dynamics in magnetic systems with anisotropic spin-orbit coupling as well as perspectives for the ultrafast control of information process in spintronic devices.
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Affiliation(s)
- Bo Liu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Wei Niu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Yongda Chen
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Xuezhong Ruan
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Zhixiong Tang
- Department of Physics, Nanjing University, Nanjing, 210093, P. R. China
| | - Xuefeng Wang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Wenqing Liu
- Department of Electronic Engineering, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Liang He
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Yao Li
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Jing Wu
- York-Nanjing Joint Center in Spintronics, Department of Electronic Engineering and Department of Physics, The University of York, York, YO10 5DD, UK
| | - Shaolong Tang
- Department of Physics, Nanjing University, Nanjing, 210093, P. R. China
| | - Jun Du
- Department of Physics, Nanjing University, Nanjing, 210093, P. R. China
| | - Rong Zhang
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
| | - Yongbing Xu
- Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093, P. R. China
- York-Nanjing Joint Center in Spintronics, Department of Electronic Engineering and Department of Physics, The University of York, York, YO10 5DD, UK
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17
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Battiato M, Minár J, Wang W, Ndiaye W, Richter MC, Heckmann O, Mariot JM, Parmigiani F, Hricovini K, Cacho C. Distinctive Picosecond Spin Polarization Dynamics in Bulk Half Metals. PHYSICAL REVIEW LETTERS 2018; 121:077205. [PMID: 30169049 DOI: 10.1103/physrevlett.121.077205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Indexed: 06/08/2023]
Abstract
Femtosecond laser excitations in half-metal (HM) compounds are theoretically predicted to induce an exotic picosecond spin dynamics. In particular, conversely to what is observed in conventional metals and semiconductors, the thermalization process in HMs leads to a long living partially thermalized configuration characterized by three Fermi-Dirac distributions for the minority, majority conduction, and majority valence electrons, respectively. Remarkably, these distributions have the same temperature but different chemical potentials. This unusual thermodynamic state is causing a persistent nonequilibrium spin polarization only well above the Fermi energy. Femtosecond spin dynamics experiments performed on Fe_{3}O_{4} by time- and spin-resolved photoelectron spectroscopy support our model. Furthermore, the spin polarization response proves to be very robust and it can be adopted to selectively test the bulk HM character in a wide range of compounds.
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Affiliation(s)
- M Battiato
- School of Physical and Mathematical Sciences, Physics and Applied Physics, Nanyang Technological University, 21 Nanyang Link, Singapore, Singapore
- Institute of Solid State Physics, Technische Universität Wien, Wiedner Hauptstraße 8, 1040 Vienna, Austria
| | - J Minár
- New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen, Czech Republic
| | - W Wang
- Department of Physics, Biology and Chemistry, Linköping University, 581 83 Linköping, Sweden
| | - W Ndiaye
- Laboratoire de Physique des Matériaux et des Surfaces, Université de Cergy-Pontoise, 5 mail Gay-Lussac, 95031 Cergy-Pontoise, France
| | - M C Richter
- Laboratoire de Physique des Matériaux et des Surfaces, Université de Cergy-Pontoise, 5 mail Gay-Lussac, 95031 Cergy-Pontoise, France
- DRF, IRAMIS, SPEC-CNRS/UMR 3680, Bâtiment 772, L'Orme des Merisiers, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - O Heckmann
- Laboratoire de Physique des Matériaux et des Surfaces, Université de Cergy-Pontoise, 5 mail Gay-Lussac, 95031 Cergy-Pontoise, France
- DRF, IRAMIS, SPEC-CNRS/UMR 3680, Bâtiment 772, L'Orme des Merisiers, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - J-M Mariot
- Sorbonne Université, CNRS (UMR 7614), Laboratoire de Chimie Physique-Matière et Rayonnement, 4 place Jussieu, 75252 Paris Cedex 05, France
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - F Parmigiani
- Dipartimento di Fisica, Università degli Studi di Trieste, via A. Valerio 2, 34127 Trieste, Italy
- Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, 34149 Basovizza, Italy
- International Faculty, Universität zu Köln, 50937 Köln, Germany
| | - K Hricovini
- Laboratoire de Physique des Matériaux et des Surfaces, Université de Cergy-Pontoise, 5 mail Gay-Lussac, 95031 Cergy-Pontoise, France
- DRF, IRAMIS, SPEC-CNRS/UMR 3680, Bâtiment 772, L'Orme des Merisiers, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - C Cacho
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, United Kingdom
- Central Laser Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom
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18
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Biswas S. Charge ordering in the metal-insulator transition of V-doped CrO 2 in the rutile structure. J Mol Model 2018; 24:111. [PMID: 29666955 DOI: 10.1007/s00894-018-3647-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 04/02/2018] [Indexed: 10/17/2022]
Abstract
Electronic, magnetic, and structural properties of pure and V-doped CrO2 were extensively investigated utilizing density functional theory. Usually, pure CrO2 is a half-metallic ferromagnet with conductive spin majority species and insulating spin minority species. This system remains in its half-metallic ferromagnetic phase even at 50% V-substitution for Cr within the crystal. The V-substituted compound Cr0.5V0.5O2 encounters metal-insulator transition upon the application of on-site Coulomb repulsion U = 7 eV preserving its ferromagnetism in the insulating phase. It is revealed in this study that Cr3+-V5+ charge ordering accompanied by the transfer of the single V-3d electron to the Cr-3dt2g orbitals triggers metal-insulator transition in Cr0.5V0.5O2. The ferromagnetism of Cr0.5V0.5O2 in the insulating phase arises predominantly due to strong Hund's coupling between the occupied electrons in the Cr-t2g states. Besides this, the ferromagnetic Curie temperature (Tc) decreases significantly due to V-substitution. Interestingly, a structural distortion is observed due to tilting of CrO6 or VO6 octahedra across the metal-insulator transition of Cr0.5V0.5O2. Graphical abstract The V-doped compound Cr0.5V0.5O2 is found a half-metallic ferromagnet (HMF) in the absence of on-site Coulomb interaction (U). This HMF behavor maintains up to U = 6 eV. Eventually, this system encounters metal-insulator transition (MIT) upon the application of U = 7 eV with a band gap of Eg ~ 0.31 eV. Nevertheless, applications of higher U widen the band gaps. In this figure, calculated total (black), Cr-3d (red), V-3d (violet), and O-2p (blue) DOS of Cr0.5V0.5O2 for U = 8 eV are illustrated. The system is insulating with a band gap of Eg ~ 0.7 eV.
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Affiliation(s)
- Sarajit Biswas
- Department of Physics, Taki Government College, Taki, North 24, Parganas, West Bengal, 743429, India.
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19
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Dewhurst JK, Elliott P, Shallcross S, Gross EKU, Sharma S. Laser-Induced Intersite Spin Transfer. NANO LETTERS 2018; 18:1842-1848. [PMID: 29424230 DOI: 10.1021/acs.nanolett.7b05118] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Laser pulses induce spin-selective charge flow that we show to generate dramatic changes in the magnetic structure of materials, including a switching of magnetic order from antiferromagnetic (AFM) to transient ferromagnetic (FM) in multisub-lattice systems. The microscopic mechanism underpinning this ultrafast switching of magnetic order is dominated by spin-selective charge transfer from one magnetic sublattice to another. Because this spin modulation is purely optical in nature (i.e., not mediated indirectly via the spin-orbit interaction) this is one of the fastest means of manipulating spin by light. We further demonstrate this mechanism to be universally applicable to AFM, FM, and ferri-magnets in both multilayer and bulk geometry and provide three rules that encapsulate early-time magnetization dynamics of multisub-lattice systems.
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Affiliation(s)
- John Kay Dewhurst
- Max-Planck Institut für Microstrukture Physics , Weinberg 2 , D-06120 Halle , Germany
| | - Peter Elliott
- Max-Planck Institut für Microstrukture Physics , Weinberg 2 , D-06120 Halle , Germany
| | - Sam Shallcross
- Lehrstuhl für Theoretische Festkörperphysik , Staudstrasse 7-B2 , 91058 Erlangen , Germany
| | - Eberhard K U Gross
- Max-Planck Institut für Microstrukture Physics , Weinberg 2 , D-06120 Halle , Germany
| | - Sangeeta Sharma
- Max-Planck Institut für Microstrukture Physics , Weinberg 2 , D-06120 Halle , Germany
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20
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Shim JH, Ali Syed A, Kim CH, Lee KM, Park SY, Jeong JR, Kim DH, Eon Kim D. Ultrafast giant magnetic cooling effect in ferromagnetic Co/Pt multilayers. Nat Commun 2017; 8:796. [PMID: 28986562 PMCID: PMC5630601 DOI: 10.1038/s41467-017-00816-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 07/28/2017] [Indexed: 11/09/2022] Open
Abstract
The magnetic cooling effect originates from a large change in entropy by the forced magnetization alignment, which has long been considered to be utilized as an alternative environment-friendly cooling technology compared to conventional refrigeration. However, an ultimate timescale of the magnetic cooling effect has never been studied yet. Here, we report that a giant magnetic cooling (up to 200 K) phenomenon exists in the Co/Pt nano-multilayers on a femtosecond timescale during the photoinduced demagnetization and remagnetization, where the disordered spins are more rapidly aligned, and thus magnetically cooled, by the external magnetic field via the lattice-spin interaction in the multilayer system. These findings were obtained by the extensive analysis of time-resolved magneto-optical responses with systematic variation of laser fluence as well as external field strength and direction. Ultrafast giant magnetic cooling observed in the present study can enable a new avenue to the realization of ultrafast magnetic devices.The forced alignment of magnetic moments leads to a large change in entropy, which can be used to reduce the temperature of a material. Here, the authors show that this magnetic cooling effect occurs on a femtosecond time scale in cobalt-platinum nano-multilayers.
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Affiliation(s)
- Je-Ho Shim
- Department of Physics, Chungbuk National University, Cheongju, 361-763, South Korea
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 790-784, South Korea
- Max Planck Center for Attosecond Science, Max Planck POSTECH/KOREA Research Initiative, Pohang, 790-784, South Korea
| | - Akbar Ali Syed
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 790-784, South Korea
- Max Planck Center for Attosecond Science, Max Planck POSTECH/KOREA Research Initiative, Pohang, 790-784, South Korea
| | - Chul-Hoon Kim
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 790-784, South Korea
- Max Planck Center for Attosecond Science, Max Planck POSTECH/KOREA Research Initiative, Pohang, 790-784, South Korea
- Department of Advanced Materials Chemistry, Korea University, Sejong, 339-700, South Korea
| | - Kyung Min Lee
- Department of Material Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 305-764, South Korea
| | - Seung-Young Park
- Spin Engineering Physics Team, Korea Basic Science Institute, Daejeon, 305-806, South Korea
| | - Jong-Ryul Jeong
- Department of Material Science and Engineering and Graduate School of Energy Science and Technology, Chungnam National University, Daejeon, 305-764, South Korea
| | - Dong-Hyun Kim
- Department of Physics, Chungbuk National University, Cheongju, 361-763, South Korea.
| | - Dong Eon Kim
- Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang, 790-784, South Korea.
- Max Planck Center for Attosecond Science, Max Planck POSTECH/KOREA Research Initiative, Pohang, 790-784, South Korea.
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21
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Zhang S, Jin Z, Liu X, Zhao W, Lin X, Jing C, Ma G. Photoinduced terahertz radiation and negative conductivity dynamics in Heusler alloy Co 2MnSn film. OPTICS LETTERS 2017; 42:3080-3083. [PMID: 28809877 DOI: 10.1364/ol.42.003080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We report the broadband terahertz (THz) radiation in ferromagnetic half-metallic Heusler alloy Co2MnSn thin film upon the irradiation of a femtosecond laser pulse at room temperature. The magnetic-, sample symmetry-, and pump fluence-dependent THz emission reveals that the THz radiation is originated from the magnetic-dipole radiation, i.e., the light-induced subpicosecond demagnetization. In addition, by optical pump-THz probe spectroscopy, we found that the photoexcited increase of the scattering rate of hot carriers thereby leads to the photoinduced negative THz conductivity in Co2MnSn thin film.
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22
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Fognini A, Michlmayr TU, Vaterlaus A, Acremann Y. Laser-induced ultrafast spin current pulses: a thermodynamic approach. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:214002. [PMID: 28441145 DOI: 10.1088/1361-648x/aa6a76] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ultrafast demagnetization process allows for the generation of femtosecond spin current pulses. Here, we present a thermodynamic model of the spin current generation process, based on the chemical potential gradients as the driving force for the spin current. We demonstrate that the laser-induced spin current can be estimated by an easy to understand diffusion model.
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Affiliation(s)
- A Fognini
- Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft 2628 CJ, The Netherlands
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23
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Hellman F, Hoffmann A, Tserkovnyak Y, Beach GSD, Fullerton EE, Leighton C, MacDonald AH, Ralph DC, Arena DA, Dürr HA, Fischer P, Grollier J, Heremans JP, Jungwirth T, Kimel AV, Koopmans B, Krivorotov IN, May SJ, Petford-Long AK, Rondinelli JM, Samarth N, Schuller IK, Slavin AN, Stiles MD, Tchernyshyov O, Thiaville A, Zink BL. Interface-Induced Phenomena in Magnetism. REVIEWS OF MODERN PHYSICS 2017; 89:025006. [PMID: 28890576 PMCID: PMC5587142 DOI: 10.1103/revmodphys.89.025006] [Citation(s) in RCA: 181] [Impact Index Per Article: 25.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
This article reviews static and dynamic interfacial effects in magnetism, focusing on interfacially-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking at interfaces. It provides a historical background and literature survey, but focuses on recent progress, identifying the most exciting new scientific results and pointing to promising future research directions. It starts with an introduction and overview of how basic magnetic properties are affected by interfaces, then turns to a discussion of charge and spin transport through and near interfaces and how these can be used to control the properties of the magnetic layer. Important concepts include spin accumulation, spin currents, spin transfer torque, and spin pumping. An overview is provided to the current state of knowledge and existing review literature on interfacial effects such as exchange bias, exchange spring magnets, spin Hall effect, oxide heterostructures, and topological insulators. The article highlights recent discoveries of interface-induced magnetism and non-collinear spin textures, non-linear dynamics including spin torque transfer and magnetization reversal induced by interfaces, and interfacial effects in ultrafast magnetization processes.
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Affiliation(s)
- Frances Hellman
- Department of Physics, University of California, Berkeley, Berkeley, California 94720, USA; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Axel Hoffmann
- Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Yaroslav Tserkovnyak
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Geoffrey S D Beach
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Eric E Fullerton
- Center for Memory and Recording Research, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0401, USA
| | - Chris Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Allan H MacDonald
- Department of Physics, University of Texas at Austin, Austin, Texas 78712-0264, USA
| | - Daniel C Ralph
- Physics Department, Cornell University, Ithaca, New York 14853, USA; Kavli Institute at Cornell, Cornell University, Ithaca, New York 14853, USA
| | - Dario A Arena
- Department of Physics, University of South Florida, Tampa, Florida 33620-7100, USA
| | - Hermann A Dürr
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Peter Fischer
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA; Physics Department, University of California, 1156 High Street, Santa Cruz, California 94056, USA
| | - Julie Grollier
- Unité Mixte de Physique CNRS/Thales and Université Paris Sud 11, 1 Avenue Fresnel, 91767 Palaiseau, France
| | - Joseph P Heremans
- Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, Ohio 43210, USA; Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210, USA; Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Tomas Jungwirth
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Praha 6, Czech Republic; School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Alexey V Kimel
- Radboud University, Institute for Molecules and Materials, Nijmegen 6525 AJ, The Netherlands
| | - Bert Koopmans
- Department of Applied Physics, Center for NanoMaterials, COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Ilya N Krivorotov
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Steven J May
- Department of Materials Science & Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA
| | - Amanda K Petford-Long
- Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, Illinois 60208, USA
| | - James M Rondinelli
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
| | - Nitin Samarth
- Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Ivan K Schuller
- Department of Physics and Center for Advanced Nanoscience, University of California, San Diego, La Jolla, California 92093, USA; Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093, USA
| | - Andrei N Slavin
- Department of Physics, Oakland University, Rochester, Michigan 48309, USA
| | - Mark D Stiles
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6202, USA
| | - Oleg Tchernyshyov
- Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - André Thiaville
- Laboratoire de Physique des Solides, UMR CNRS 8502, Université Paris-Sud, 91405 Orsay, France
| | - Barry L Zink
- Department of Physics and Astronomy, University of Denver, Denver, CO 80208, USA
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24
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Element Selective Probe of the Ultra-Fast Magnetic Response to an Element Selective Excitation in Fe-Ni Compounds Using a Two-Color FEL Source. PHOTONICS 2017. [DOI: 10.3390/photonics4010006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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25
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Carva K, Baláž P, Radu I. Laser-Induced Ultrafast Magnetic Phenomena. HANDBOOK OF MAGNETIC MATERIALS 2017. [DOI: 10.1016/bs.hmm.2017.09.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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26
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Ultrafast laser induced local magnetization dynamics in Heusler compounds. Sci Rep 2016; 6:38911. [PMID: 27966585 PMCID: PMC5155284 DOI: 10.1038/srep38911] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/14/2016] [Indexed: 11/30/2022] Open
Abstract
The overarching goal of the field of femtomagnetism is to control, via laser light, the magnetic structure of matter on a femtosecond time scale. The temporal limits to the light-magnetism interaction are governed by the fact that the electron spin interacts indirectly with light, with current studies showing a laser induced global loss in the magnetic moment on a time scale of the order of a few 100 s of femtoseconds. In this work, by means of ab-initio calculations, we show that more complex magnetic materials - we use the example of the Heusler and half-Heusler alloys - allow for purely optical excitations to cause a significant change in the local moments on the order of 5 fs. This, being purely optical in nature, represents the ultimate mechanism for the short time scale manipulation of spins. Furthermore, we demonstrate that qualitative behaviour of this rich magnetic response to laser light can be deduced from the ground-state spectrum, thus providing a route to tailoring the response of some complex magnetic materials, like the Heuslers, to laser light by the well established methods for material design from ground-state calculations.
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27
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Tsuyama T, Chakraverty S, Macke S, Pontius N, Schüßler-Langeheine C, Hwang HY, Tokura Y, Wadati H. Photoinduced Demagnetization and Insulator-to-Metal Transition in Ferromagnetic Insulating BaFeO_{3} Thin Films. PHYSICAL REVIEW LETTERS 2016; 116:256402. [PMID: 27391735 DOI: 10.1103/physrevlett.116.256402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Indexed: 06/06/2023]
Abstract
We studied the electronic and magnetic dynamics of ferromagnetic insulating BaFeO_{3} thin films by using pump-probe time-resolved resonant x-ray reflectivity at the Fe 2p edge. By changing the excitation density, we found two distinctly different types of demagnetization with a clear threshold behavior. We assigned the demagnetization change from slow (∼150 ps) to fast (<70 ps) to a transition into a metallic state induced by laser excitation. These results provide a novel approach for locally tuning magnetic dynamics. In analogy to heat-assisted magnetic recording, metallization can locally tune the susceptibility for magnetic manipulation, allowing one to spatially encode magnetic information.
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Affiliation(s)
- T Tsuyama
- Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Chiba 277-8581, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Hongo, Tokyo 113-8656, Japan
| | - S Chakraverty
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Institute of Nano Science and Technology, Phase-10, Sector-64, Mohali, Punjab 160062, India
| | - S Macke
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - N Pontius
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - C Schüßler-Langeheine
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany
| | - H Y Hwang
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Y Tokura
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Hongo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - H Wadati
- Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Chiba 277-8581, Japan
- Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Hongo, Tokyo 113-8656, Japan
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28
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Ovsyannikov SV, Bykov M, Bykova E, Kozlenko DP, Tsirlin AA, Karkin AE, Shchennikov VV, Kichanov SE, Gou H, Abakumov AM, Egoavil R, Verbeeck J, McCammon C, Dyadkin V, Chernyshov D, van Smaalen S, Dubrovinsky LS. Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation. Nat Chem 2016; 8:501-8. [PMID: 27102685 DOI: 10.1038/nchem.2478] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 02/15/2016] [Indexed: 11/09/2022]
Abstract
Phase transitions that occur in materials, driven, for instance, by changes in temperature or pressure, can dramatically change the materials' properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here we investigate a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling below ∼150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in electrical resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temperature and a spin canting at 85 K that gives rise to spontaneous magnetization. We discuss possible mechanisms of this transition and compare it with the trimeronic charge ordering observed in magnetite below the Verwey transition temperature.
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Affiliation(s)
- Sergey V Ovsyannikov
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany
| | - Maxim Bykov
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany.,Laboratory of Crystallography, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany
| | - Elena Bykova
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany.,Laboratory of Crystallography, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany
| | | | - Alexander A Tsirlin
- National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia.,Experimental Physics VI, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - Alexander E Karkin
- Institute of Metal Physics, Russian Academy of Sciences, Urals Division, GSP-170, 18 S. Kovalevskaya Str., Yekaterinburg 620041, Russia
| | - Vladimir V Shchennikov
- Institute of Metal Physics, Russian Academy of Sciences, Urals Division, GSP-170, 18 S. Kovalevskaya Str., Yekaterinburg 620041, Russia.,Institute for Solid State Chemistry, Russian Academy of Sciences, Urals Division, 91 Pervomayskaya Str., Yekaterinburg 620990, Russia
| | | | - Huiyang Gou
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany.,Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China
| | - Artem M Abakumov
- Electron Microscopy for Materials Research (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.,Department of Chemistry, Moscow State University, Leninskie Gory 1-3, Moscow 119991, Russia
| | - Ricardo Egoavil
- Electron Microscopy for Materials Research (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Johan Verbeeck
- Electron Microscopy for Materials Research (EMAT), University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - Catherine McCammon
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany
| | - Vadim Dyadkin
- Swiss-Norwegian Beamlines at the European Synchrotron Radiation Facility, 38000, Grenoble, France
| | - Dmitry Chernyshov
- Swiss-Norwegian Beamlines at the European Synchrotron Radiation Facility, 38000, Grenoble, France
| | - Sander van Smaalen
- Laboratory of Crystallography, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany
| | - Leonid S Dubrovinsky
- Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstrasse 30, D-95447, Bayreuth, Germany
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29
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Arkhipov DI, Gordeev SV, Dzidziguri EL, Osmolovskii MG, Osmolovskaya OM. Optimization of CrO2 magnetic characteristics in the process of hydrothermal synthesis using nucleating agents of complex structure. RUSS J GEN CHEM+ 2016. [DOI: 10.1134/s107036321604037x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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30
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Xu TS, Ju L, Wang Z, Ren C, Kang SS, Qiao SZ, Li TX, Yan SS, Mei LM. Disorder-enhanced spin polarization of the Zn 1−xCo xO 1−v concentrated magnetic semiconductor. RSC Adv 2016. [DOI: 10.1039/c5ra20520d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Amorphous concentrated magnetic semiconductor Zn0.32Co0.68O1−v (v refers to oxygen vacancies) thin film was investigated by magnetic and electrical transport measurements as well as Andreev reflection spectroscopy.
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Affiliation(s)
- T. S. Xu
- School of Physics and Electrical Engineering
- Anyang Normal College
- Anyang 455000
- People's Republic of China
- School of Physics
| | - L. Ju
- School of Physics and Electrical Engineering
- Anyang Normal College
- Anyang 455000
- People's Republic of China
| | - Z. Wang
- School of Physics and Electrical Engineering
- Anyang Normal College
- Anyang 455000
- People's Republic of China
| | - C. Ren
- National Laboratory for Superconductivity
- Institute of Physics
- Chinese Academy of Sciences
- Beijing 100190
- People's Republic of China
| | - S. S. Kang
- School of Physics
- National Key Laboratory of Crystal Materials
- Shandong University
- Jinan 250100
- People's Republic of China
| | - S. Z. Qiao
- School of Physics
- National Key Laboratory of Crystal Materials
- Shandong University
- Jinan 250100
- People's Republic of China
| | - T. X. Li
- School of Physics and Electrical Engineering
- Anyang Normal College
- Anyang 455000
- People's Republic of China
| | - S. S. Yan
- School of Physics
- National Key Laboratory of Crystal Materials
- Shandong University
- Jinan 250100
- People's Republic of China
| | - L. M. Mei
- School of Physics
- National Key Laboratory of Crystal Materials
- Shandong University
- Jinan 250100
- People's Republic of China
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31
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Frietsch B, Bowlan J, Carley R, Teichmann M, Wienholdt S, Hinzke D, Nowak U, Carva K, Oppeneer PM, Weinelt M. Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal. Nat Commun 2015; 6:8262. [PMID: 26355196 PMCID: PMC4579838 DOI: 10.1038/ncomms9262] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 08/04/2015] [Indexed: 01/26/2023] Open
Abstract
The Heisenberg–Dirac intra-atomic exchange coupling is responsible for the formation of the atomic spin moment and thus the strongest interaction in magnetism. Therefore, it is generally assumed that intra-atomic exchange leads to a quasi-instantaneous aligning process in the magnetic moment dynamics of spins in separate, on-site atomic orbitals. Following ultrashort optical excitation of gadolinium metal, we concurrently record in photoemission the 4f magnetic linear dichroism and 5d exchange splitting. Their dynamics differ by one order of magnitude, with decay constants of 14 versus 0.8 ps, respectively. Spin dynamics simulations based on an orbital-resolved Heisenberg Hamiltonian combined with first-principles calculations explain the particular dynamics of 5d and 4f spin moments well, and corroborate that the 5d exchange splitting traces closely the 5d spin-moment dynamics. Thus gadolinium shows disparate dynamics of the localized 4f and the itinerant 5d spin moments, demonstrating a breakdown of their intra-atomic exchange alignment on a picosecond timescale. Due the strength of the intra-atomic exchange interaction, it is generally assumed that alignment of spin moments in intra-atomic orbitals is quasi-instantaneous. Here, the authors demonstrate the breakdown of this relation between the 4f and 5d electrons in gadolinium following ultrashort optical excitation.
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Affiliation(s)
- B Frietsch
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - J Bowlan
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - R Carley
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - M Teichmann
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.,Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin, Germany
| | - S Wienholdt
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - D Hinzke
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - U Nowak
- Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
| | - K Carva
- Department of Physics and Astronomy, Uppsala University, PO Box 516, 75120 Uppsala, Sweden.,Charles University, Faculty of Mathematics and Physics, DCMP, Ke Karlovu 5, CZ-12116 Prague 2, Czech Republic
| | - P M Oppeneer
- Department of Physics and Astronomy, Uppsala University, PO Box 516, 75120 Uppsala, Sweden
| | - M Weinelt
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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Bernal-Villamil I, Gallego S. Electronic phase transitions in ultrathin magnetite films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:293202. [PMID: 26153727 DOI: 10.1088/0953-8984/27/29/293202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Magnetite (Fe3O4) shows singular electronic and magnetic properties, resulting from complex electron-electron and electron-phonon interactions that involve the interplay of charge, orbital and spin degrees of freedom. The Verwey transition is a manifestation of these interactions, with a puzzling connection between the low temperature charge ordered state and the dynamic charge fluctuations still present above the transition temperature. Here we explore how these rich physical phenomena are affected by thin film geometries, particularly focusing on the ultimate size limit defined by thicknesses below the minimum bulk unit cell. On one hand, we address the influence of extended defects, such as surfaces or antiphase domains, on the novel features exhibited by thin films. On the other, we try to isolate the effect of the reduced thickness on the electronic and magnetic properties. We will show that a distinct phase diagram and novel charge distributions emerge under reduced dimensions, while holding the local high magnetic moments. Altogether, thin film geometries offer unique possibilities to understand the complex interplay of short- and long-range orders in the Verwey transition. Furthermore, they arise as interesting candidates for the exploitation of the rich physics of magnetite in devices that demand nanoscale geometries, additionally offering novel functionalities based on their distinct properties with respect to the bulk form.
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Affiliation(s)
- I Bernal-Villamil
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid, Spain
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33
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Bernal-Villamil I, Gallego S. Charge order at magnetite Fe₃O₄(0 0 1): surface and Verwey phase transitions. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:012001. [PMID: 25419695 DOI: 10.1088/0953-8984/27/1/012001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
At ambient conditions, the Fe3O4(0 0 1) surface shows a (√2 × √2)R45° reconstruction that has been proposed as the surface analog of the bulk phase below the Verwey transition temperature, T(V). The reconstruction disappears at a high temperature, T(S), through a second order transition. We calculate the temperature evolution of the surface electronic structure based on a reduced bulk unit cell of P2/m symmetry that contains the main features of the bulk charge distribution. We demonstrate that the insulating surface gap arises from the large demand of charge of the surface O, at difference with that of the bulk. Furthermore, it is coupled to a significant restructuration that inhibits the formation of trimerons at the surface. An alternative bipolaronic charge distribution emerges below T(S), introducing a competition between surface and bulk charge orders below T(V).
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Affiliation(s)
- I Bernal-Villamil
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, 28049 Madrid, Spain
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34
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Sun X, Pratt A, Yamauchi Y. Half-metallicity induced by boron adsorption on an Fe3O4(100) surface. Phys Chem Chem Phys 2015; 17:15386-91. [DOI: 10.1039/c5cp02466h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spin polarization of the Fe3O4(100) surface is enhanced by B adsorption through the opening of the spin-up band gap.
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Affiliation(s)
- X. Sun
- Key Laboratory of Strongly-Coupled Quantum Matter Physics
- Chinese Academy of Sciences
- School of Physical Sciences
- University of Science and Technology of China
- Hefei
| | - A. Pratt
- National Institute for Materials Science
- Tsukuba
- Japan
- Department of Physics
- University of York
| | - Y. Yamauchi
- National Institute for Materials Science
- Tsukuba
- Japan
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35
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Boschini F, Hedayat H, Piovera C, Dallera C, Gupta A, Carpene E. A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:013909. [PMID: 25638099 DOI: 10.1063/1.4906756] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO2 single crystals as a benchmark.
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Affiliation(s)
- F Boschini
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - H Hedayat
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - C Piovera
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - C Dallera
- Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
| | - A Gupta
- Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487, USA
| | - E Carpene
- CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano, Italy
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36
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Using ultrashort optical pulses to couple ferroelectric and ferromagnetic order in an oxide heterostructure. Nat Commun 2014; 5:5832. [DOI: 10.1038/ncomms6832] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 11/12/2014] [Indexed: 11/09/2022] Open
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37
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De Sarkar S, Sensarma R, Sengupta K. A perturbative renormalization group approach to driven quantum systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:325602. [PMID: 25054233 DOI: 10.1088/0953-8984/26/32/325602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We use a perturbative momentum shell renormalization group (RG) approach to study the properties of a driven quantum system at zero temperature. To illustrate the technique, we consider a bosonic ϕ(4) theory with an arbitrary time dependent interaction parameter λ(t) = λ f(ω0t), where ω0 is the drive frequency and we derive the RG equations for the system using a Keldysh diagrammatic technique. We show that the scaling of ω0 is analogous to that of temperature for a system in thermal equilibrium and its presence provides a cutoff scale for the RG flow. We analyze the resultant RG equations, derive an analytical condition for such a drive to take the system out of the gaussian regime, and show that the onset of the non-gaussian regime occurs concomitantly with the appearance of non-perturbative mode coupling terms in the effective action of the system. We supplement the above-mentioned results by obtaining them from equations of motion of the bosons and discuss their significance for systems near critical points described by time-dependent Landau-Ginzburg theories.
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Affiliation(s)
- Sangita De Sarkar
- Theoretical Physics Department, Indian Association for the Cultivation of Science, Kolkata 700032, India
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38
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Resolving the role of femtosecond heated electrons in ultrafast spin dynamics. Sci Rep 2014; 4:3980. [PMID: 24496221 PMCID: PMC3913971 DOI: 10.1038/srep03980] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 01/15/2014] [Indexed: 11/08/2022] Open
Abstract
Magnetization manipulation is essential for basic research and applications. A fundamental question is, how fast can the magnetization be reversed in nanoscale magnetic storage media. When subject to an ultrafast laser pulse, the speed of the magnetization dynamics depends on the nature of the energy transfer pathway. The order of the spin system can be effectively influenced through spin-flip processes mediated by hot electrons. It has been predicted that as electrons drive spins into the regime close to almost total demagnetization, characterized by a loss of ferromagnetic correlations near criticality, a second slower demagnetization process takes place after the initial fast drop of magnetization. By studying FePt, we unravel the fundamental role of the electronic structure. As the ferromagnet Fe becomes more noble in the FePt compound, the electronic structure is changed and the density of states around the Fermi level is reduced, thereby driving the spin correlations into the limit of critical fluctuations. We demonstrate the impact of the electrons and the ferromagnetic interactions, which allows a general insight into the mechanisms of spin dynamics when the ferromagnetic state is highly excited, and identifies possible recording speed limits in heat-assisted magnetization reversal.
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39
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Sun X, Li SD, Wang B, Kurahashi M, Pratt A, Yamauchi Y. Significant variation of surface spin polarization through group IV atom (C, Si, Ge, Sn) adsorption on Fe3O4(100). Phys Chem Chem Phys 2014; 16:95-102. [PMID: 24220002 DOI: 10.1039/c3cp53272k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The adsorption of group IV atoms (C, Si, Ge, Sn) on the magnetite Fe3O4(100) surface is investigated by density functional theory calculations. All these atoms prefer to bond to the surface oxygen atom which has no tetrahedral Fe(A) neighbor. The spin-up surface states of clean Fe3O4(100) are completely removed and half-metallicity is recovered by C adsorption. The spin-up band gap of the C-adsorbed Fe3O4(100) surface is wider than that of the H-adsorbed one and closer to the value of bulk Fe3O4. For the adsorption of other group IV atoms, the adsorbate-substrate interaction decreases and the adsorbate-adsorbate interaction increases with the increase of atomic number Z. As a consequence, the spin polarization varies from -99.4% (C adsorption) to +44.2% (Sn adsorption) for the electronic states of the adsorbed atom integrated from -0.5 eV to the Fermi level. The ability to tune the surface spin polarization by the choice of adsorbate is of significance for magnetite-based spintronic devices.
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Affiliation(s)
- X Sun
- Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
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40
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Zhang GP, George TF. Thermal or nonthermal? That is the question for ultrafast spin switching in GdFeCo. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:366002. [PMID: 23934847 DOI: 10.1088/0953-8984/25/36/366002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
GdFeCo is among the most interesting magnets for producing laser-induced femtosecond magnetism, where light can switch its spin moment from one direction to another. This paper aims to set a criterion for the thermal/nonthermal mechanism: we propose to use the Fermi-Dirac distribution function as a reliable criterion. A precise value for the thermalization time is needed, and through a two-level model, we show that since there is no direct connection between the laser helicity and the definition of thermal/nonthermal processes, the helicity is a poor criterion for differentiating a thermal from a nonthermal process. In addition, we propose a four-site model system (Gd2Fe2) for investigating the transient ferromagnetic ordering between Gd and Fe ions. We find that states of two different kinds can allow such an ordering. One state is a pure ferromagnetic state with ferromagnetic ordering among all the ions, and the other is the short-ranged ferromagnetic ordering of a pair of Gd and Fe ions.
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Affiliation(s)
- G P Zhang
- Department of Physics, Indiana State University, Terre Haute, IN 47809, USA.
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41
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Pandey A, Ueland BG, Yeninas S, Kreyssig A, Sapkota A, Zhao Y, Helton JS, Lynn JW, McQueeney RJ, Furukawa Y, Goldman AI, Johnston DC. Coexistence of half-metallic itinerant ferromagnetism with local-moment antiferromagnetism in Ba0.60K0.40Mn2As2. PHYSICAL REVIEW LETTERS 2013; 111:047001. [PMID: 23931395 DOI: 10.1103/physrevlett.111.047001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Indexed: 06/02/2023]
Abstract
Magnetization, nuclear magnetic resonance, high-resolution x-ray diffraction, and magnetic field-dependent neutron diffraction measurements reveal a novel magnetic ground state of Ba0.60K0.40Mn2As2 in which itinerant ferromagnetism (FM) below a Curie temperature TC≈100 K arising from the doped conduction holes coexists with collinear antiferromagnetism (AFM) of the Mn local moments that order below a Néel temperature TN=480 K. The FM ordered moments are aligned in the tetragonal ab plane and are orthogonal to the AFM ordered Mn moments that are aligned along the c axis. The magnitude and nature of the low-T FM ordered moment correspond to complete polarization of the doped-hole spins (half-metallic itinerant FM) as deduced from magnetization and ab-plane electrical resistivity measurements.
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Affiliation(s)
- Abhishek Pandey
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
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42
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Turgut E, La-o-Vorakiat C, Shaw JM, Grychtol P, Nembach HT, Rudolf D, Adam R, Aeschlimann M, Schneider CM, Silva TJ, Murnane MM, Kapteyn HC, Mathias S. Controlling the competition between optically induced ultrafast spin-flip scattering and spin transport in magnetic multilayers. PHYSICAL REVIEW LETTERS 2013; 110:197201. [PMID: 23705737 DOI: 10.1103/physrevlett.110.197201] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Indexed: 05/06/2023]
Abstract
The study of ultrafast dynamics in magnetic materials provides rich opportunities for greater fundamental understanding of correlated phenomena in solid-state matter, because many of the basic microscopic mechanisms involved are as-yet unclear and are still being uncovered. Recently, two different possible mechanisms have been proposed to explain ultrafast laser induced magnetization dynamics: spin currents and spin-flip scattering. In this work, we use multilayers of Fe and Ni with different metals and insulators as the spacer material to conclusively show that spin currents can have a significant contribution to optically induced magnetization dynamics, in addition to spin-flip scattering processes. Moreover, we can control the competition between these two processes, and in some cases completely suppress interlayer spin currents as a sample undergoes rapid demagnetization. Finally, by reversing the order of the Fe/Ni layers, we experimentally show that spin currents are directional in our samples, predominantly flowing from the top to the bottom layer.
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Affiliation(s)
- Emrah Turgut
- Department of Physics and JILA, University of Colorado, Boulder and NIST, Colorado 80309, USA
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43
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Ultrafast magnetization enhancement in metallic multilayers driven by superdiffusive spin current. Nat Commun 2012; 3:1037. [PMID: 22948819 DOI: 10.1038/ncomms2029] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 07/30/2012] [Indexed: 11/09/2022] Open
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44
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Balzer M, Gdaniec N, Potthoff M. Krylov-space approach to the equilibrium and nonequilibrium single-particle Green's function. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:035603. [PMID: 22183787 DOI: 10.1088/0953-8984/24/3/035603] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The zero-temperature single-particle Green's function of correlated fermion models with moderately large Hilbert-space dimensions can be calculated by means of Krylov-space techniques. The conventional Lanczos approach consists of finding the ground state in a first step, followed by an approximation for the resolvent of the Hamiltonian in a second step. We analyze the character of this approximation and discuss a numerically exact variant of the Lanczos method which is formulated in the time domain. This method is extended to obtain the nonequilibrium single-particle Green's function defined on the Keldysh-Matsubara contour in the complex time plane which describes the system's nonperturbative response to a sudden parameter switch in the Hamiltonian. The proposed method will be important as an exact-diagonalization solver in the context of self-consistent or variational cluster-embedding schemes. For the recently developed nonequilibrium cluster-perturbation theory, we discuss its efficient implementation and demonstrate the feasibility of the Krylov-based solver. The dissipation of a strong local magnetic excitation into a non-interacting bath is considered as an example for applications.
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Affiliation(s)
- Matthias Balzer
- I Institut für Theoretische Physik, Universität Hamburg, Hamburg, Germany
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45
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Zhao HB, Talbayev D, Ma X, Ren YH, Venimadhav A, Li Q, Lüpke G. Coherent spin precession via photoinduced antiferromagnetic interactions in La0.67Ca0.33MnO3. PHYSICAL REVIEW LETTERS 2011; 107:207205. [PMID: 22181766 DOI: 10.1103/physrevlett.107.207205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Indexed: 05/31/2023]
Abstract
Pronounced spin precessions are observed in a geometry with negligible canting of the magnetization in ferromagnetic La(0.67)Ca(0.33)MnO(3) thin films using the time-resolved magneto-optical Kerr effect. The precession amplitude monotonically decreases with increasing field, indicating that the coherent spin rotation may be triggered by a transient exchange field and not by demagnetization and/or anisotropy field modulation. We attribute the transient exchange field to emergent antiferromagnetic interactions due to charge transfer and modification of the kinetic energy of e(g) electrons under optical excitation.
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Affiliation(s)
- H B Zhao
- Department of Optical Science and Engineering, Fudan University, Shanghai, China.
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46
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Walter M, Walowski J, Zbarsky V, Münzenberg M, Schäfers M, Ebke D, Reiss G, Thomas A, Peretzki P, Seibt M, Moodera JS, Czerner M, Bachmann M, Heiliger C. Seebeck effect in magnetic tunnel junctions. NATURE MATERIALS 2011; 10:742-746. [PMID: 21785418 DOI: 10.1038/nmat3076] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 06/20/2011] [Indexed: 05/31/2023]
Abstract
Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, that is, the combination of magneto- and thermoelectric effects. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge-based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In this respect, it is the analogue to the tunnelling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configurations are of the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature. The geometric centre of the electronic density of states relative to the Fermi level determines the size of the Seebeck effect. Experimentally, we realized 8.8% magneto-Seebeck effect, which results from a voltage change of about -8.7 μV K⁻¹ from the antiparallel to the parallel direction close to the predicted value of -12.1 μV K⁻¹. In contrast to the spin-Seebeck effect, it can be measured as a voltage change directly without conversion of a spin current.
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47
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Wietstruk M, Melnikov A, Stamm C, Kachel T, Pontius N, Sultan M, Gahl C, Weinelt M, Dürr HA, Bovensiepen U. Hot-electron-driven enhancement of spin-lattice coupling in Gd and Tb 4f ferromagnets observed by femtosecond x-ray magnetic circular dichroism. PHYSICAL REVIEW LETTERS 2011; 106:127401. [PMID: 21517350 DOI: 10.1103/physrevlett.106.127401] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Indexed: 05/30/2023]
Abstract
Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4f electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to 50 times compared to equilibrium.
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Affiliation(s)
- Marko Wietstruk
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, BESSY II, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
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48
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Zhao Q, Wen G, Liu Z, Fan Y, Zou G, Li L, Zheng R, Ringer SP, Mao HK. Synthesis of dense, single-crystalline CrO2 nanowire arrays using AAO template-assisted chemical vapor deposition. NANOTECHNOLOGY 2011; 22:125603. [PMID: 21325713 DOI: 10.1088/0957-4484/22/12/125603] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
High-density, vertically aligned CrO(2) nanowire arrays were obtained via atmospheric-pressure CVD assisted by AAO templates. The CrO(2) nanowire arrays show remarkably enhanced coercivity compared with CrO(2) films or bulk. It was found that the length of the nanowires is greatly influenced by the pore diameter of the AAO template used. The growth mechanism and the pore size dependence of the CrO(2) nanowire arrays are discussed. The present method provides a useful approach for the synthesis of CrO(2) nanowire arrays. Such highly ordered nanowire arrays within an AAO template may have important applications in ultrahigh-density perpendicular magnetic recording devices and the mass production of spintronic nanodevices.
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Affiliation(s)
- Qiang Zhao
- State Key Laboratory of Superhard Materials, Jilin University, Changchun, People's Republic of China
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49
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Steil D, Alebrand S, Roth T, Krauss M, Kubota T, Oogane M, Ando Y, Schneider HC, Aeschlimann M, Cinchetti M. Band-structure-dependent demagnetization in the Heusler alloy Co₂Mn(1-x)FexSi. PHYSICAL REVIEW LETTERS 2010; 105:217202. [PMID: 21231346 DOI: 10.1103/physrevlett.105.217202] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Indexed: 05/30/2023]
Abstract
We investigate the ultrafast demagnetization for two Heusler alloys (Co₂Mn(1-x)FexSi) with a different lineup of the minority band gap and the Fermi level. Even though electronic spin-flip transitions are partially blocked by the band gap in one compound, the respective magnetization dynamics, as measured by the time-resolved Kerr effect, are remarkably similar. Based on a dynamical model that includes momentum and spin-dependent carrier scattering, we show that the magnetization dynamics are dominated by hole spin-flip processes, which are not influenced by the gap.
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Affiliation(s)
- Daniel Steil
- Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67653 Kaiserslautern, Germany
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50
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Battiato M, Carva K, Oppeneer PM. Superdiffusive spin transport as a mechanism of ultrafast demagnetization. PHYSICAL REVIEW LETTERS 2010; 105:027203. [PMID: 20867735 DOI: 10.1103/physrevlett.105.027203] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Indexed: 05/23/2023]
Abstract
We propose a semiclassical model for femtosecond laser-induced demagnetization due to spin-polarized excited electron diffusion in the superdiffusive regime. Our approach treats the finite elapsed time and transport in space between multiple electronic collisions exactly, as well as the presence of several metal films in the sample. Solving the derived transport equation numerically we show that this mechanism accounts for the experimentally observed demagnetization within 200 fs in Ni, without the need to invoke any angular momentum dissipation channel.
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Affiliation(s)
- M Battiato
- Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
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