1
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Jiang M, Asahara H, Sato S, Kanaki T, Yamasaki H, Ohya S, Tanaka M. Efficient full spin-orbit torque switching in a single layer of a perpendicularly magnetized single-crystalline ferromagnet. Nat Commun 2019; 10:2590. [PMID: 31197145 PMCID: PMC6565668 DOI: 10.1038/s41467-019-10553-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 05/20/2019] [Indexed: 11/23/2022] Open
Abstract
Spin-orbit torque (SOT), which is induced by an in-plane electric current via large spin-orbit coupling, enables an innovative method of manipulating the magnetization of ferromagnets by means of current injection. In conventional SOT bilayer systems, the magnetization switching efficiency strongly depends on the interface quality and the strength of the intrinsic spin Hall Effect. Here, we demonstrate highly efficient full SOT switching achieved by applying a current in a single layer of perpendicularly magnetized ferromagnetic semiconductor GaMnAs with an extremely small current density of ∼3.4 × 105 A cm-2, which is two orders of magnitude smaller than that needed in typical metal bilayer systems. This low required current density is attributed to the intrinsic bulk inversion asymmetry of GaMnAs as well as its high-quality single crystallinity and large spin polarization. Our findings will contribute to advancements in the electrical control of magnetism and its practical application in semiconductor devices.
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Affiliation(s)
- Miao Jiang
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Hirokatsu Asahara
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shoichi Sato
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Toshiki Kanaki
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Hiroki Yamasaki
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Shinobu Ohya
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- Center for Spintronics Research Network (CSRN), Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - Masaaki Tanaka
- Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
- Center for Spintronics Research Network (CSRN), Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
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2
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Han W, Chen BJ, Gu B, Zhao GQ, Yu S, Wang XC, Liu QQ, Deng Z, Li WM, Zhao JF, Cao LP, Peng Y, Shen X, Zhu XH, Yu RC, Maekawa S, Uemura YJ, Jin CQ. Li(Cd,Mn)P: a new cadmium based diluted ferromagnetic semiconductor with independent spin & charge doping. Sci Rep 2019; 9:7490. [PMID: 31097727 PMCID: PMC6522530 DOI: 10.1038/s41598-019-43754-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 12/13/2018] [Indexed: 11/09/2022] Open
Abstract
We report a new diluted ferromagnetic semiconductor Li1+y(Cd,Mn)P, wherein carrier is doped via excess Li while spin is doped by isovalence substitution of Mn2+ into Cd2+. The extended Cd 4d-orbitals lead to more itinerant characters of Li1+y(Cd,Mn)P than that of analogous Li1+y(Zn,Mn)P. A higher Curie temperature of 45 K than that for Li1+y(Zn,Mn)P is obtained in Li1+y(Cd,Mn)P polycrystalline samples by Arrott plot technique. The p-type carriers are determined by Hall effect measurements. The first principle calculations and X-ray diffraction measurements indicate that occupation of excess Li is at Cd sites rather than the interstitial site. Consequently holes are doped by excess Li substitution. More interestingly Li1+y(Cd,Mn)P shows a very low coercive field (<100 Oe) and giant negative magnetoresistance (~80%) in ferromagnetic state that will benefit potential spintronics applications.
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Affiliation(s)
- W Han
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China.,Department of Physics and Electronic Engineering, Hebei Normal University for Nationalities, Chengde, 067000, China
| | - B J Chen
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - B Gu
- Kavli Institute for Theoretical Sciences & CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
| | - G Q Zhao
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - S Yu
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - X C Wang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Q Q Liu
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Z Deng
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. .,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China.
| | - W M Li
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - J F Zhao
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - L P Cao
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Y Peng
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.,Department of Materials Science & Engineering, Sichuan University, Chengdu, China
| | - X Shen
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - X H Zhu
- Department of Materials Science & Engineering, Sichuan University, Chengdu, China
| | - R C Yu
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - S Maekawa
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
| | - Y J Uemura
- Department of Physics, Columbia University, New York, New York, 10027, USA
| | - C Q Jin
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. .,School of Physics, University of Chinese Academy of Sciences, Beijing, 100190, China. .,Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China.
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3
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Golovatski EA, Flatté ME. Interaction of two domain walls during spin-torque-induced coherent motion. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:315802. [PMID: 29916815 DOI: 10.1088/1361-648x/aacd84] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We show that the application of a spin-polarized current to a double p domain wall system with a variable distance between the walls results in an interaction between the two domain walls. The transmission spectrum changes from that of a spin-dependent resonant double barrier to one like a [Formula: see text] wall. In addition, the spin torque on each individual wall creates coupled motion in the domain walls. The walls move independently with a fast speed at large separations, but slow considerably at small separations.
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Affiliation(s)
- E A Golovatski
- Department of Physics, Central College, Pella, IA 50129, United States of America. Optical Science and Technology Center and Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, United States of America
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4
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Zhao GQ, Lin CJ, Deng Z, Gu GX, Yu S, Wang XC, Gong ZZ, Uemura YJ, Li YQ, Jin CQ. Single Crystal Growth and Spin Polarization Measurements of Diluted Magnetic Semiconductor (BaK)(ZnMn) 2As 2. Sci Rep 2017; 7:14473. [PMID: 29101360 PMCID: PMC5670247 DOI: 10.1038/s41598-017-08394-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 07/12/2017] [Indexed: 11/09/2022] Open
Abstract
Recently a new diluted magnetic semiconductor, (Ba,K)(Zn,Mn)2As2 (BZA), with high Curie temperature was discovered, showing an independent spin and charge-doping mechanism. This makes BZA a promising material for spintronics devices. We report the successful growth of a BZA single crystal for the first time in this study. An Andreev reflection junction, which can be used to evaluate spin polarization, was fabricated based on the BZA single crystal. A 66% spin polarization of the BZA single crystal was obtained by Andreev reflection spectroscopy analysis.
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Affiliation(s)
- G Q Zhao
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China
- University of Chinese Academy of Sciences, Beijing, 100190, China
| | - C J Lin
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China
| | - Z Deng
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China
| | - G X Gu
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China
| | - S Yu
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China
| | - X C Wang
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China
| | - Z Z Gong
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Yasutomo J Uemura
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Y Q Li
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China.
- University of Chinese Academy of Sciences, Beijing, 100190, China.
| | - C Q Jin
- Institute of Physics, Chinese Academy of Sciences; Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China.
- University of Chinese Academy of Sciences, Beijing, 100190, China.
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5
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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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6
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Guan T, Lin C, Yang C, Shi Y, Ren C, Li Y, Weng H, Dai X, Fang Z, Yan S, Xiong P. Evidence for Half-Metallicity in n-type HgCr2Se4. PHYSICAL REVIEW LETTERS 2015; 115:087002. [PMID: 26340201 DOI: 10.1103/physrevlett.115.087002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Indexed: 06/05/2023]
Abstract
High quality HgCr2Se4 single crystals have been investigated by magnetization, electron transport, and Andreev reflection spectroscopy. In the ferromagnetic ground state, the saturation magnetic moment of each unit cell corresponds to an integer number of electron spins (3 μB/Cr3+), and the Hall effect measurements suggest n-type charge carriers. Spin polarizations as high as 97% were obtained from fits of the differential conductance spectra of HgCr2Se4/Pb junctions with the modified Blonder-Tinkham-Klapwijk theory. The temperature and bias-voltage dependencies of the subgap conductance are consistent with recent theoretical calculations based on spin active scatterings at a superconductor-half-metal interface. Our results suggest that n-HgCr2Se4 is a half-metal, in agreement with theoretical calculations that also predict undoped HgCr2Se4 is a magnetic Weyl semimetal.
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Affiliation(s)
- Tong Guan
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Chaojing Lin
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Chongli Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Youguo Shi
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Cong Ren
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yongqing Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Hongming Weng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Xi Dai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Zhong Fang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
| | - Shishen Yan
- School of Physics, Shandong University, Jinan 250100, China
| | - Peng Xiong
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
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7
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Curiale J, Lemaître A, Ulysse C, Faini G, Jeudy V. Spin drift velocity, polarization, and current-driven domain-wall motion in (Ga,Mn)(As,P). PHYSICAL REVIEW LETTERS 2012; 108:076604. [PMID: 22401234 DOI: 10.1103/physrevlett.108.076604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Indexed: 05/31/2023]
Abstract
Current-driven domain-wall motion is studied in (Ga,Mn)(As,P) ferromagnetic semiconducting tracks with perpendicular anisotropy. A linear steady state flow regime is observed over a large temperature range of the ferromagnetic phase (0.1T(c)<T<T(c)). Close to 0 K, the domain-wall velocity is found to coincide with the spin drift velocity. This result is obtained below the intrinsic threshold for domain-wall motion which implies a nonadiabatic contribution to the spin transfer torque. The current spin polarization is deduced close to 0 K and to T(c). It suggests that the temperature dependence of the spin polarization can be inferred from the domain-wall dynamics.
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Affiliation(s)
- J Curiale
- Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, 91405 Orsay, France
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8
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Jeudy V, Curiale J, Adam JP, Thiaville A, Lemaître A, Faini G. Current induced domain wall motion in GaMnAs close to the Curie temperature. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:446004. [PMID: 22005254 DOI: 10.1088/0953-8984/23/44/446004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Domain wall dynamics produced by spin transfer torques is investigated in (Ga, Mn)As ferromagnetic semiconducting tracks with perpendicular anisotropy, close to the Curie temperature. The domain wall velocities are found to follow a linear flow regime which only slightly varies with temperature. Using the Döring inequality, boundaries of the spin polarization of the current are deduced. A comparison with the predictions of the mean field k·p theory leads to an estimation of the carrier density whose value is compatible with results published in the literature. The spin polarization of the current and the magnetization of the magnetic atoms present similar temperature variations. This leads to a weak temperature dependence of the spin drift velocity and thus of the domain wall velocity. A combined study of field- and current-driven motion and deformation of magnetic domains reveals a motion of domain walls in the steady state regime without transition to the precessional regime. The ratio between the non-adiabatic torque β and the Gilbert damping factor α is shown to remain close to unity.
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Affiliation(s)
- V Jeudy
- Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, 91405 Orsay, France.
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9
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Degrave JP, Schmitt AL, Selinsky RS, Higgins JM, Keavney DJ, Jin S. Spin polarization measurement of homogeneously doped Fe(1-x)Co(x)Si nanowires by Andreev reflection spectroscopy. NANO LETTERS 2011; 11:4431-4437. [PMID: 21923114 DOI: 10.1021/nl2026426] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report a general method for determining the spin polarization from nanowire materials using Andreev reflection spectroscopy implemented with a Nb superconducting contact and common electron-beam lithography device fabrication techniques. This method was applied to magnetic semiconducting Fe(1-x)Co(x)Si alloy nanowires with x̅ = 0.23, and the average spin polarization extracted from 6 nanowire devices is 28 ± 7% with a highest observed value of 35%. Local-electrode atom probe tomography (APT) confirms the homogeneous distribution of Co atoms in the FeSi host lattice, and X-ray magnetic circular dichroism (XMCD) establishes that the elemental origin of magnetism in this strongly correlated electron system is due to Co atoms.
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Affiliation(s)
- John P Degrave
- Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States
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10
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Song C, Sperl M, Utz M, Ciorga M, Woltersdorf G, Schuh D, Bougeard D, Back CH, Weiss D. Proximity induced enhancement of the Curie temperature in hybrid spin injection devices. PHYSICAL REVIEW LETTERS 2011; 107:056601. [PMID: 21867085 DOI: 10.1103/physrevlett.107.056601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Indexed: 05/31/2023]
Abstract
We investigate the increase of the Curie temperature T(C) in a lateral spin injection geometry where the ferromagnetic (Ga,Mn)As injector and detector contacts are capped by a thin iron film. Because of interlayer coupling between Fe and (Ga,Mn)As T(C) gets enhanced by nearly 100% for the thinnest (Ga,Mn)As films. The use of the proximity effect might pave the way for practical implementation of spintronic devices.
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Affiliation(s)
- C Song
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany
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11
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Jaworski CM, Yang J, Mack S, Awschalom DD, Myers RC, Heremans JP. Spin-seebeck effect: a phonon driven spin distribution. PHYSICAL REVIEW LETTERS 2011; 106:186601. [PMID: 21635114 DOI: 10.1103/physrevlett.106.186601] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Indexed: 05/30/2023]
Abstract
Here we report on measurements of the spin-Seebeck effect in GaMnAs over an extended temperature range alongside the thermal conductivity, specific heat, magnetization, and thermoelectric power. The amplitude of the spin-Seebeck effect in GaMnAs scales with the thermal conductivity of the GaAs substrate and the phonon-drag contribution to the thermoelectric power of the GaMnAs, demonstrating that phonons drive the spin redistribution. A phenomenological model involving phonon-magnon drag explains the spatial and temperature dependence of the measured spin distribution.
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Affiliation(s)
- C M Jaworski
- Department of Mechanical Engineering, The Ohio State University, Columbus, 43210, USA
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12
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dos Santos LF, Gobato YG, Teodoro MD, Lopez-Richard V, Marques GE, Brasil MJSP, Orlita M, Kunc J, Maude DK, Henini M, Airey RJ. Circular polarization in a non-magnetic resonant tunneling device. NANOSCALE RESEARCH LETTERS 2011; 6:101. [PMID: 21711613 PMCID: PMC3211145 DOI: 10.1186/1556-276x-6-101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 01/25/2011] [Indexed: 05/31/2023]
Abstract
We have investigated the polarization-resolved photoluminescence (PL) in an asymmetric n-type GaAs/AlAs/GaAlAs resonant tunneling diode under magnetic field parallel to the tunnel current. The quantum well (QW) PL presents strong circular polarization (values up to -70% at 19 T). The optical emission from GaAs contact layers shows evidence of highly spin-polarized two-dimensional electron and hole gases which affects the spin polarization of carriers in the QW. However, the circular polarization degree in the QW also depends on various other parameters, including the g-factors of the different layers, the density of carriers along the structure, and the Zeeman and Rashba effects.
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Affiliation(s)
- Lara F dos Santos
- Physics Department, Federal University of São Carlos, São Carlos, Brazil
| | - Yara Galvão Gobato
- Physics Department, Federal University of São Carlos, São Carlos, Brazil
| | - Márcio D Teodoro
- Physics Department, Federal University of São Carlos, São Carlos, Brazil
| | | | - Gilmar E Marques
- Physics Department, Federal University of São Carlos, São Carlos, Brazil
| | | | - Milan Orlita
- Grenoble High Magnet Field Laboratory, Grenoble, France
- Institute of Physics, Charles University, Ke Karlovu 5, 121 16 Praha 2, Czech Republic
| | - Jan Kunc
- Grenoble High Magnet Field Laboratory, Grenoble, France
- Institute of Physics, Charles University, Ke Karlovu 5, 121 16 Praha 2, Czech Republic
| | | | - Mohamed Henini
- School of Physics and Astronomy, Nottingham Nanotechnology and Nanoscience Centre, University of Nottingham, Nottingham, NG7 2RD, UK
| | - Robert J Airey
- EPSRC National Centre for III-V Technologies, The University of Sheffield, Sheffield, UK
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13
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Jaworski CM, Yang J, Mack S, Awschalom DD, Heremans JP, Myers RC. Observation of the spin-Seebeck effect in a ferromagnetic semiconductor. NATURE MATERIALS 2010; 9:898-903. [PMID: 20871608 DOI: 10.1038/nmat2860] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 08/22/2010] [Indexed: 05/29/2023]
Abstract
Reducing the heat generated in traditional electronics is a chief motivation for the development of spin-based electronics, called spintronics. Spin-based transistors that do not strictly rely on the raising or lowering of electrostatic barriers can overcome scaling limits in charge-based transistors. Spin transport in semiconductors might also lead to dissipation-less information transfer with pure spin currents. Despite these thermodynamic advantages, little experimental literature exists on the thermal aspects of spin transport in solids. A recent and surprising exception was the discovery of the spin-Seebeck effect, reported as a measurement of a redistribution of spins along the length of a sample of permalloy (NiFe) induced by a temperature gradient. This macroscopic spatial distribution of spins is, surprisingly, many orders of magnitude larger than the spin diffusion length, which has generated strong interest in the thermal aspects of spin transport. Here, the spin-Seebeck effect is observed in a ferromagnetic semiconductor, GaMnAs, which allows flexible design of the magnetization directions, a larger spin polarization, and measurements across the magnetic phase transition. This effect is observed even in the absence of longitudinal charge transport. The spatial distribution of spin currents is maintained across electrical breaks, highlighting the local nature of this thermally driven effect.
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14
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Neumaier D, Wagner K, Geissler S, Wurstbauer U, Sadowski J, Wegscheider W, Weiss D. Weak localization in ferromagnetic (Ga,Mn)as nanostructures. PHYSICAL REVIEW LETTERS 2007; 99:116803. [PMID: 17930460 DOI: 10.1103/physrevlett.99.116803] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Indexed: 05/25/2023]
Abstract
We report on the observation of weak localization in arrays of (Ga,Mn)As nanowires at millikelvin temperatures. The corresponding phase coherence length L phi is typically between 100 and 200 nm at 20 mK. Strong spin-orbit interaction in the material is manifested by a weak antilocalization correction around zero magnetic field.
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Affiliation(s)
- D Neumaier
- Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany.
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15
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Leighton C, Manno M, Cady A, Freeland JW, Wang L, Umemoto K, Wentzcovitch RM, Chen TY, Chien CL, Kuhns PL, Hoch MJR, Reyes AP, Moulton WG, Dahlberg ED, Checkelsky J, Eckert J. Composition controlled spin polarization in Co(1-x)Fe(x)S(2) alloys. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:315219. [PMID: 21694119 DOI: 10.1088/0953-8984/19/31/315219] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The transition metal (TM) chalcogenides of the form TMX(2) (X = S or Se) have been studied for decades due to their interesting electronic and magnetic properties such as metamagnetism and metal-insulator transitions. In particular, the Co(1-x)Fe(x)S(2) alloys were the subject of investigation in the 1970s due to general interest in itinerant ferromagnetism. In recent years (2000-present) it has been shown, both by electronic structure calculations and detailed experimental investigations, that Co(1-x)Fe(x)S(2) is a model system for the investigation of highly spin polarized ferromagnetism. The radically different electronic properties of the two endpoint compounds (CoS(2) is a narrow bandwidth ferromagnetic metal, while FeS(2) is a diamagnetic semiconductor), in a system forming a substitutional solid solution allows for composition control of the Fermi level relative to the spin split bands, and therefore composition-controlled conduction electron spin polarization. In essence, the recent work has shown that the concept of 'band engineering' can be applied to half-metallic ferromagnets and that high spin polarization can be deliberately engineered. Experiments reveal tunability in both sign and magnitude of the spin polarization at the Fermi level, with maximum values obtained to date of 85% at low temperatures. In this paper we review the properties of Co(1-x)Fe(x)S(2) alloys, with an emphasis on properties of relevance to half-metallicity. Crystal structure, electronic structure, synthesis, magnetic properties, transport properties, direct probes of the spin polarization, and measurements of the total density of states at the Fermi level are all discussed. We conclude with a discussion of the factors that influence, or even limit, the spin polarization, along with a discussion of opportunities and problems for future investigation, particularly with regard to fundamental studies of spintronic devices.
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Affiliation(s)
- C Leighton
- Department of Chemical Engineering and Materials Science, University of Minnesota, USA
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Abstract
Semiconductor spintronicsSpintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role. In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism. While metal spintronics has already found its niche in the computer industry—giant magnetoresistance systems are used as hard disk read heads—semiconductor spintronics is yet to demonstrate its full potential. This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spin-dependent tunneling, as well as spin relaxation and spin dynamics. The most fundamental spin-dependent interaction in nonmagnetic semiconductors is spin-orbit coupling. Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians. The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions. Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations. A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors. In view of the importance of ferromagnetic semiconductor materials, a brief discussion of diluted magnetic semiconductors is included. In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field.
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Giazotto F, Taddei F, Beltram F, Fazio R. Crossed Andreev reflection-induced magnetoresistance. PHYSICAL REVIEW LETTERS 2006; 97:087001. [PMID: 17026324 DOI: 10.1103/physrevlett.97.087001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2005] [Indexed: 05/12/2023]
Abstract
We show that very large negative magnetoresistance can be obtained in magnetic trilayers in a current-in-plane geometry owing to the existence of crossed Andreev reflection. This spin valve consists of a thin superconducting film sandwiched between two ferromagnetic layers whose magnetization is allowed to be either parallelly or antiparallelly aligned. For a suitable choice of structure parameters and nearly fully spin-polarized ferromagnets, the magnetoresistance can exceed -80%. Our results are relevant for the design and implementation of spintronic devices exploiting ferromagnet-superconductor structures.
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Zutić I, Fabian J, Erwin SC. Spin injection and detection in silicon. PHYSICAL REVIEW LETTERS 2006; 97:026602. [PMID: 16907469 DOI: 10.1103/physrevlett.97.026602] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 05/04/2006] [Indexed: 05/11/2023]
Abstract
Spin injection and detection in silicon is a difficult problem, in part because the weak spin-orbit coupling and indirect gap preclude using standard optical techniques. Two ways to overcome this difficulty are proposed, both based on spin-polarized transport across a heterojunction. Using a realistic transport model incorporating the relevant spin dynamics of both electrons and holes, it is argued that symmetry properties of the charge current can be exploited to detect electrical spin injection in silicon using currently available techniques.
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Affiliation(s)
- Igor Zutić
- Department of Physics, State University of New York at Buffalo, 14260, USA
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Kant CH, Filip AT, Swagten HJM, de Jonge WJM. Comment on "Direct measurement of the spin polarization of the magnetic semiconductor (Ga,Mn)As". PHYSICAL REVIEW LETTERS 2004; 93:169703-169704. [PMID: 15525046 DOI: 10.1103/physrevlett.93.169703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2003] [Indexed: 05/24/2023]
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