1
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Makiuchi T, Hioki T, Shimizu H, Hoshi K, Elyasi M, Yamamoto K, Yokoi N, Serga AA, Hillebrands B, Bauer GEW, Saitoh E. Persistent magnetic coherence in magnets. Nat Mater 2024; 23:627-632. [PMID: 38321239 DOI: 10.1038/s41563-024-01798-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Accepted: 01/05/2024] [Indexed: 02/08/2024]
Abstract
When excited, the magnetization in a magnet precesses around the field in an anticlockwise manner on a timescale governed by viscous magnetization damping, after which any information carried by the initial actuation seems to be lost. This damping appears to be a fundamental bottleneck for the use of magnets in information processing. However, here we demonstrate the recall of the magnetization-precession phase after times that exceed the damping timescale by two orders of magnitude using dedicated two-colour microwave pump-probe experiments for a Y3Fe5O12 microstructured film. Time-resolved magnetization state tomography confirms the persistent magnetic coherence by revealing a double-exponential decay of magnetization correlation. We attribute persistent magnetic coherence to a feedback effect, that is, coherent coupling of the uniform precession with long-lived excitations at the minima of the spin-wave dispersion relation. Our finding liberates magnetic systems from the strong damping in nanostructures that has limited their use in coherent information storage and processing.
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Affiliation(s)
- T Makiuchi
- Department of Applied Physics, University of Tokyo, Tokyo, Japan
- Quantum-Phase Electronics Center, University of Tokyo, Tokyo, Japan
| | - T Hioki
- Department of Applied Physics, University of Tokyo, Tokyo, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan
| | - H Shimizu
- Department of Applied Physics, University of Tokyo, Tokyo, Japan
| | - K Hoshi
- Department of Applied Physics, University of Tokyo, Tokyo, Japan
- Institute for AI and Beyond, University of Tokyo, Tokyo, Japan
| | - M Elyasi
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan
| | - K Yamamoto
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan
| | - N Yokoi
- Department of Applied Physics, University of Tokyo, Tokyo, Japan
- Institute for AI and Beyond, University of Tokyo, Tokyo, Japan
| | - A A Serga
- Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern-Landau, Kaiserslautern, Germany
| | - B Hillebrands
- Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern-Landau, Kaiserslautern, Germany
| | - G E W Bauer
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan
- Kavli Institute for Theoretical Sciences, University of the Chinese Academy of Sciences, Beijing, China
| | - E Saitoh
- Department of Applied Physics, University of Tokyo, Tokyo, Japan.
- Quantum-Phase Electronics Center, University of Tokyo, Tokyo, Japan.
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan.
- Institute for AI and Beyond, University of Tokyo, Tokyo, Japan.
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan.
- RIKEN Center for Emergent Matter Science, Wako, Japan.
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2
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Obata R, Kosugi M, Kikkawa T, Kuroyama K, Yokouchi T, Shiomi Y, Maruyama S, Hirakawa K, Saitoh E, Haruyama J. Coexistence of Quantum-Spin-Hall and Quantum-Hall-Topological-Insulating States in Graphene/hBN on SrTiO 3 Substrate. Adv Mater 2024:e2311339. [PMID: 38324142 DOI: 10.1002/adma.202311339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 01/30/2024] [Indexed: 02/08/2024]
Abstract
SrTiO3 (STO) substrate, a perovskite oxide material known for its high dielectric constant (ε), facilitates the observation of various (high-temperature) quantum phenomena. A quantum Hall topological insulating (QHTI) state, comprising two copies of QH states with antiparallel two ferromagnetic edge-spin overlap protected by the U(1) axial rotation symmetry of spin polarization, has recently been achieved in low magnetic field (B) even as high as approximately 100K in a monolayer graphene/thin hexagonal boron nitride (hBN) spacer placed on an STO substrate, thanks to the high ε of STO. Despite the use of the heavy STO substrate, however, proximity-induced quantum spin Hall (QSH) states in two-dimensional (2D) TI phases, featuring a topologically protected helical edge spin phase within time-reversal-symmetry, have not been confirmed. Here, with the use of a monolayer hBN spacer, we reveal the coexistence of QSH (at B = 0T) and QHTI (at B ≠ 0) states in the same single graphene sample placed on an STO, with a crossover regime between the two at low B. It is also classified that the different symmetries of the two non-trivial helical edge spin phases in the two states lead to different interaction with electron-puddle quantum dots, caused by a local surface pocket of the STO, in the crossover regime, resulting in a spin dephasing only for the QHTI state. The results obtained using STO substrates open the doors to investigations of novel QH spin states with different symmetries and their correlations with quantum phenomena. This exploration holds value for potential applications in spintronic devices. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- R Obata
- Faculty of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa, 252-5258, Japan
| | - M Kosugi
- Faculty of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa, 252-5258, Japan
| | - T Kikkawa
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - K Kuroyama
- Institute for Industrial Sciences, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo, 153-8505, Japan
| | - T Yokouchi
- Department of Basic Science, The University of Tokyo, 3-6-1 Komaba Meguro-ku, Tokyo, 153-8902, Japan
| | - Y Shiomi
- Department of Basic Science, The University of Tokyo, 3-6-1 Komaba Meguro-ku, Tokyo, 153-8902, Japan
| | - S Maruyama
- Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - K Hirakawa
- Institute for Industrial Sciences, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo, 153-8505, Japan
| | - E Saitoh
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- Institute for AI and Beyond, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan
| | - J Haruyama
- Faculty of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa, 252-5258, Japan
- Institute for Industrial Sciences, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo, 153-8505, Japan
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3
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Schmitt C, Rajan A, Beneke G, Kumar A, Sparmann T, Meer H, Bednarz B, Ramos R, Niño MA, Foerster M, Saitoh E, Kläui M. Mechanisms of Electrical Switching of Ultrathin CoO/Pt Bilayers. Nano Lett 2024; 24:1471-1476. [PMID: 38216142 PMCID: PMC10853954 DOI: 10.1021/acs.nanolett.3c02890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 12/21/2023] [Accepted: 12/21/2023] [Indexed: 01/14/2024]
Abstract
We study current-induced switching of the Néel vector in CoO/Pt bilayers to understand the underlying antiferromagnetic switching mechanism. Surprisingly, we find that for ultrathin CoO/Pt bilayers electrical pulses along the same path can lead to an increase or decrease of the spin Hall magnetoresistance signal, depending on the current density of the pulse. By comparing these results to XMLD-PEEM imaging of the antiferromagnetic domain structure before and after the application of current pulses, we reveal the details of the reorientation of the Néel vector in ultrathin CoO(4 nm). This allows us to understand how opposite resistance changes can result from a thermomagnetoelastic switching mechanism. Importantly, our spatially resolved imaging shows that regions where the current pulses are applied and regions further away exhibit different switched spin structures, which can be explained by a spin-orbit torque-based switching mechanism that can dominate in very thin films.
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Affiliation(s)
- Christin Schmitt
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Adithya Rajan
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Grischa Beneke
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Aditya Kumar
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Tobias Sparmann
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Hendrik Meer
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Beatrice Bednarz
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
| | - Rafael Ramos
- WPI-Advanced
Institute for Materials Research, Tohoku
University, Sendai 980-8577, Japan
| | - Miguel Angel Niño
- ALBA
Synchrotron Light Facility, 08290 Cerdanyola del Valles (Barcelona), Spain
| | - Michael Foerster
- ALBA
Synchrotron Light Facility, 08290 Cerdanyola del Valles (Barcelona), Spain
| | - Eiji Saitoh
- WPI-Advanced
Institute for Materials Research, Tohoku
University, Sendai 980-8577, Japan
- Institute
for Materials Research, Tohoku University, Sendai 980-8577, Japan
- The
Institute of AI and Beyond, The University
of Tokyo, Tokyo 113-8656, Japan
- Center
for
Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Department
of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Mathias Kläui
- Institute
of Physics, Johannes Gutenberg University
Mainz, 55099 Mainz, Germany
- Graduate
School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
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4
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Umeda M, Chudo H, Imai M, Sato N, Saitoh E. Temperature-variable apparatus for measuring Barnett field. Rev Sci Instrum 2023; 94:063906. [PMID: 37862522 DOI: 10.1063/5.0142318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 05/31/2023] [Indexed: 10/22/2023]
Abstract
We have developed experimental equipment for observing the Barnett effect, in which mechanical rotation magnetizes an object, at low temperatures. A sample in a rotor is rotated bidirectionally using a temperature-controlled high-pressure gas. The stray field generated from the sample due to the Barnett effect was detected using a fluxgate magnetic sensor with a sensitivity on the order of several picoteslas, even at low temperatures. By replacing the rotor with a solenoid coil, the magnetic susceptibility of the sample was estimated from the stray field to be of the same order of magnitude as that due to the Barnett effect. The Barnett field was estimated using the dipole model. To assess the performance of the setup at low temperatures, measurements were performed on commercial magnetite (Fe3O4) nanogranules. We confirmed the accordance of the g' factor between the experimental results using the present setup and those of our previous study performed at room temperature.
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Affiliation(s)
- Maki Umeda
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Hiroyuki Chudo
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Masaki Imai
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Nana Sato
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Eiji Saitoh
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Institute for AI and Beyond, The University of Tokyo, Tokyo 113-8656, Japan
- Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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5
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Rongione E, Gueckstock O, Mattern M, Gomonay O, Meer H, Schmitt C, Ramos R, Kikkawa T, Mičica M, Saitoh E, Sinova J, Jaffrès H, Mangeney J, Goennenwein STB, Geprägs S, Kampfrath T, Kläui M, Bargheer M, Seifert TS, Dhillon S, Lebrun R. Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin-phonon interactions. Nat Commun 2023; 14:1818. [PMID: 37002246 PMCID: PMC10066367 DOI: 10.1038/s41467-023-37509-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 03/20/2023] [Indexed: 04/03/2023] Open
Abstract
Antiferromagnetic materials have been proposed as new types of narrowband THz spintronic devices owing to their ultrafast spin dynamics. Manipulating coherently their spin dynamics, however, remains a key challenge that is envisioned to be accomplished by spin-orbit torques or direct optical excitations. Here, we demonstrate the combined generation of broadband THz (incoherent) magnons and narrowband (coherent) magnons at 1 THz in low damping thin films of NiO/Pt. We evidence, experimentally and through modeling, two excitation processes of spin dynamics in NiO: an off-resonant instantaneous optical spin torque in (111) oriented films and a strain-wave-induced THz torque induced by ultrafast Pt excitation in (001) oriented films. Both phenomena lead to the emission of a THz signal through the inverse spin Hall effect in the adjacent heavy metal layer. We unravel the characteristic timescales of the two excitation processes found to be < 50 fs and > 300 fs, respectively, and thus open new routes towards the development of fast opto-spintronic devices based on antiferromagnetic materials.
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Affiliation(s)
- E Rongione
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, F-91767, Palaiseau, France
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - O Gueckstock
- Institute of Physics, Freie Universität Berlin, D-14195, Berlin, Germany
| | - M Mattern
- Institut für Physik und Astronomie, Universität Potsdam, D-14476, Potsdam, Germany
| | - O Gomonay
- Institute of Physics, Johannes Gutenberg-University Mainz, D-55099, Mainz, Germany
| | - H Meer
- Institute of Physics, Johannes Gutenberg-University Mainz, D-55099, Mainz, Germany
| | - C Schmitt
- Institute of Physics, Johannes Gutenberg-University Mainz, D-55099, Mainz, Germany
| | - R Ramos
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, J-980-8577, Japan
- Centro Singular de Investigación en Química Bilóxica e Materiais Moleculares (CIQUS), Departamento de Química-Física, Universidade de Santiago de Compostela, Santiago de Compostela, 15782, Spain
| | - T Kikkawa
- Department of Applied Physics, The University of Tokyo, Tokyo, J-113-8656, Japan
| | - M Mičica
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - E Saitoh
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, J-980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo, J-113-8656, Japan
- Institute for AI and Beyond, The University of Tokyo, Tokyo, J-113-8656, Japan
| | - J Sinova
- Institute of Physics, Johannes Gutenberg-University Mainz, D-55099, Mainz, Germany
| | - H Jaffrès
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, F-91767, Palaiseau, France
| | - J Mangeney
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - S T B Goennenwein
- Department of Physics, University of Konstanz, D-78457, Konstanz, Germany
| | - S Geprägs
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, D-85748, Garching, Germany
| | - T Kampfrath
- Institute of Physics, Freie Universität Berlin, D-14195, Berlin, Germany
| | - M Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, D-55099, Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz (MAINZ), Staudingerweg 9, D-55128, Mainz, Germany
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, N-7034, Trondheim, Norway
| | - M Bargheer
- Institut für Physik und Astronomie, Universität Potsdam, D-14476, Potsdam, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie, Wilhelm-Conrad-Röntgen Campus, BESSY II, Albert-Einstein-Strasse 15, D-12489, Berlin, Germany
| | - T S Seifert
- Institute of Physics, Freie Universität Berlin, D-14195, Berlin, Germany.
| | - S Dhillon
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005, Paris, France
| | - R Lebrun
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, F-91767, Palaiseau, France.
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6
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Lee O, Yamamoto K, Umeda M, Zollitsch CW, Elyasi M, Kikkawa T, Saitoh E, Bauer GEW, Kurebayashi H. Nonlinear Magnon Polaritons. Phys Rev Lett 2023; 130:046703. [PMID: 36763415 DOI: 10.1103/physrevlett.130.046703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 09/19/2022] [Accepted: 12/07/2022] [Indexed: 06/18/2023]
Abstract
We experimentally and theoretically demonstrate that nonlinear spin-wave interactions suppress the hybrid magnon-photon quasiparticle or "magnon polariton" in microwave spectra of a yttrium iron garnet film detected by an on-chip split-ring resonator. We observe a strong coupling between the Kittel and microwave cavity modes in terms of an avoided crossing as a function of magnetic fields at low microwave input powers, but a complete closing of the gap at high powers. The experimental results are well explained by a theoretical model including the three-magnon decay of the Kittel magnon into spin waves. The gap closure originates from the saturation of the ferromagnetic resonance above the Suhl instability threshold by a coherent backreaction from the spin waves.
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Affiliation(s)
- Oscar Lee
- London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom
| | - Kei Yamamoto
- Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai 319-1195, Japan
| | - Maki Umeda
- Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai 319-1195, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Christoph W Zollitsch
- London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom
| | - Mehrdad Elyasi
- WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Sendai 980-8577, Japan
| | - Takashi Kikkawa
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Eiji Saitoh
- Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai 319-1195, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- Institute for AI and Beyond, The University of Tokyo, Tokyo 113-8656, Japan
| | - Gerrit E W Bauer
- WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Sendai 980-8577, Japan
- Kavli Institute for Theoretical Sciences, University of the Chinese Academy of Sciences, Beijing 100190, China
| | - Hidekazu Kurebayashi
- London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom
- WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Sendai 980-8577, Japan
- Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom
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7
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Lee W, Kang M, Choi JW, Kim S, Park N, Kim G, Kim Y, Saitoh E, Yoon Y, Lee S. Abnormal Seebeck Effect in Vertically Stacked 2D/2D PtSe 2 /PtSe 2 Homostructure. Adv Sci (Weinh) 2022; 9:e2203455. [PMID: 36354191 PMCID: PMC9799017 DOI: 10.1002/advs.202203455] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 09/08/2022] [Indexed: 06/16/2023]
Abstract
When a thermoelectric (TE) material is deposited with a secondary TE material, the total Seebeck coefficient of the stacked layer is generally represented by a parallel conductor model. Accordingly, when TE material layers of the same thickness are stacked vertically, the total Seebeck coefficient in the transverse direction may change in a single layer. Here, an abnormal Seebeck effect in a stacked two-dimensional (2D) PtSe2 /PtSe2 homostructure film, i.e., an extra in-plane Seebeck voltage is produced by wet-transfer stacking at the interface between the PtSe2 layers under a transverse temperature gradient is reported. This abnormal Seebeck effect is referred to as the interfacial Seebeck effect in stacked PtSe2 /PtSe2 homostructures. This effect is attributed to the carrier-interface interaction, and has independent characteristics in relation to carrier concentration. It is confirmed that the in-plane Seebeck coefficient increases as the number of stacked PtSe2 layers increase and observed a high Seebeck coefficient exceeding ≈188 µV K-1 at 300 K in a four-layer-stacked PtSe2 /PtSe2 homostructure.
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Affiliation(s)
- Won‐Yong Lee
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
- Division of Solid State ElectronicsDepartment of Electrical EngineeringUppsala UniversityUppsala75103Sweden
| | - Min‐Sung Kang
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
| | - Jae Won Choi
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
| | - Si‐Hoo Kim
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
| | - No‐Won Park
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
| | - Gil‐Sung Kim
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
| | - Yun‐Ho Kim
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
| | - Eiji Saitoh
- Department of Applied PhysicsThe University of TokyoTokyo113–8656Japan
| | - Young‐Gui Yoon
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
| | - Sang‐Kwon Lee
- Department of PhysicsCenter for Berry Curvature based New PhenomenaChung‐Ang UniversitySeoul06974Republic of Korea
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8
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Lee WY, Kang MS, Kim GS, Choi JW, Park NW, Sim Y, Kim YH, Seong MJ, Yoon YG, Saitoh E, Lee SK. Interface-Induced Seebeck Effect in PtSe 2/PtSe 2 van der Waals Homostructures. ACS Nano 2022; 16:3404-3416. [PMID: 35133142 DOI: 10.1021/acsnano.2c00359] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The Seebeck effect refers to the production of an electric voltage when different temperatures are applied on a conductor, and the corresponding voltage-production efficiency is represented by the Seebeck coefficient. We report a Seebeck effect: thermal generation of driving voltage from the heat flowing in a thin PtSe2/PtSe2 van der Waals homostructure at the interface. We refer to the effect as the interface-induced Seebeck effect. By exploiting this effect by directly attaching multilayered PtSe2 over high-resistance PtSe2 thin films as a hybridized single structure, we obtained the highly challenging in-plane Seebeck coefficient of the PtSe2 films that exhibit extremely high resistances. This direct attachment further enhanced the in-plane thermal Seebeck coefficients of the PtSe2/PtSe2 van der Waals homostructure on sapphire substrates. Consequently, we successfully enhanced the in-plane Seebeck coefficients for the PtSe2 (10 nm)/PtSe2 (2 nm) homostructure approximately 42% compared to that of a pure PtSe2 (10 nm) layer at 300 K. These findings represent a significant achievement in understanding the interface-induced Seebeck effect and provide an effective strategy for promising large-area thermoelectric energy harvesting devices using two-dimensional transition metal dichalcogenide materials, which are ideal thermoelectric platforms with high figures of merit.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Jae Won Choi
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Yumin Sim
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Yun-Ho Kim
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Maeng-Je Seong
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Young-Gui Yoon
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Eiji Saitoh
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Sang-Kwon Lee
- Department of Physics and Center for Berry Curvature based New Phenomena, Chung-Ang University, Seoul 06974, Republic of Korea
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9
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Lee WY, Park NW, Kang MS, Kim GS, Yoon YG, Lee S, Choi KY, Kim KS, Kim JH, Seong MJ, Kikkawa T, Saitoh E, Lee SK. Extrinsic Surface Magnetic Anisotropy Contribution in Pt/Y 3Fe 5O 12 Interface in Longitudinal Spin Seebeck Effect by Graphene Interlayer. ACS Appl Mater Interfaces 2021; 13:45097-45104. [PMID: 34496563 DOI: 10.1021/acsami.1c13180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A recent study found that magnetization curves for Y3Fe5O12 (YIG) slab and thick films (>20 μm thick) differed from bulk system curves by their longitudinal spin Seebeck effect in a Pt/YIG bilayer system. The deviation was due to intrinsic YIG surface magnetic anisotropy, which is difficult to adopt extrinsic surface magnetic anisotropy even when in contact with other materials on the YIG surface. This study experimentally demonstrates evidence for extrinsic YIG surface magnetic anisotropy when in contact with a diamagnetic graphene interlayer by observing the spin Seebeck effect, directly proving intrinsic YIG surface magnetic anisotropy interruption. We show the Pt/YIG bilayer system graphene interlayer role using large area single and multilayered graphenes using the longitudinal spin Seebeck effect at room temperature, and address the presence of surface magnetic anisotropy due to magnetic proximity between graphene and YIG layer. These findings suggest a promising route to understand new physics of spin Seebeck effect in spin transport.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Young-Gui Yoon
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Suheon Lee
- Deopartment of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Kwang-Yong Choi
- Deopartment of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Keun Soo Kim
- Department of Physics and Astronomy, Sejong University, Seoul 05006, Republic of Korea
| | - Jin-Hyuk Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Maeng-Je Seong
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Takashi Kikkawa
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Eiji Saitoh
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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10
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Park NW, Kim H, Lee WY, Kim GS, Kang DY, Kim TG, Saitoh E, Yoon YG, Rho H, Lee SK. Giant Thermoelectric Seebeck Coefficients in Tellurium Quantum Wires Formed Vertically in an Aluminum Oxide Layer by Electrical Breakdown. J Phys Chem Lett 2021; 12:8212-8219. [PMID: 34415767 DOI: 10.1021/acs.jpclett.1c01842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
High efficiency thermoelectric (TE) materials still require high thermopower for energy harvesting applications. A simple elemental metallic semiconductor, tellurium (Te), has been considered critical to realize highly efficient TE conversion due to having a large effective band valley degeneracy. This paper demonstrates a novel approach to directly probe the out-of-plane Seebeck coefficient for one-dimensional Te quantum wires (QWs) formed locally in the aluminum oxide layer by well-controlled electrical breakdown at 300 K. Surprisingly, the out-of-plane Seebeck coefficient for these Te QWs ≈ 0.8 mV/K at 300 K. This thermopower enhancement for Te QWs is due to Te intrinsic nested band structure and enhanced energy filtering at Te/AO interfaces. Theoretical calculations support the enhanced high Seebeck coefficient for elemental Te QWs in the oxide layer. The local-probed observation and detecting methodology used here offers a novel route to designing enhanced thermoelectric materials and devices in the future.
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Affiliation(s)
- No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Hanul Kim
- Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Dae Yun Kang
- School of Electrical Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Tae Geun Kim
- School of Electrical Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Young-Gui Yoon
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Heesuk Rho
- Department of Physics, Research Institute of Physics and Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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11
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Chen Y, Sato M, Tang Y, Shiomi Y, Oyanagi K, Masuda T, Nambu Y, Fujita M, Saitoh E. Triplon current generation in solids. Nat Commun 2021; 12:5199. [PMID: 34465792 PMCID: PMC8408157 DOI: 10.1038/s41467-021-25494-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 08/04/2021] [Indexed: 11/09/2022] Open
Abstract
A triplon refers to a fictitious particle that carries angular momentum S=1 corresponding to the elementary excitation in a broad class of quantum dimerized spin systems. Such systems without magnetic order have long been studied as a testing ground for quantum properties of spins. Although triplons have been found to play a central role in thermal and magnetic properties in dimerized magnets with singlet correlation, a spin angular momentum flow carried by triplons, a triplon current, has not been detected yet. Here we report spin Seebeck effects induced by a triplon current: triplon spin Seebeck effect, using a spin-Peierls system CuGeO3. The result shows that the heating-driven triplon transport induces spin current whose sign is positive, opposite to the spin-wave cases in magnets. The triplon spin Seebeck effect persists far below the spin-Peierls transition temperature, being consistent with a theoretical calculation for triplon spin Seebeck effects.
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Affiliation(s)
- Yao Chen
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - Masahiro Sato
- Department of Physics, Ibaraki University, Mito, Ibaraki, Japan.
| | - Yifei Tang
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - Yuki Shiomi
- Department of Basic Science, The University of Tokyo, Tokyo, Japan
| | - Koichi Oyanagi
- Institute for Materials Research, Tohoku University, Sendai, Japan
- Faculty of Science and Engineering, Iwate University, Morioka, Japan
| | - Takatsugu Masuda
- Institute of Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan
| | - Yusuke Nambu
- Institute for Materials Research, Tohoku University, Sendai, Japan
- FOREST, Japan Science and Technology Agency, Kawaguchi, Saitama, Japan
- Organization for Advanced Studies, Tohoku University, Sendai, Japan
| | - Masaki Fujita
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai, Japan.
- Department of Applied Physics, The University of Tokyo, Tokyo, Japan.
- Institute for AI and Beyond, The University of Tokyo, Tokyo, Japan.
- Advanced Institute for Materials Research, Tohoku University, Sendai, Japan.
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan.
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12
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Jiang N, Nii Y, Arisawa H, Saitoh E, Ohe J, Onose Y. Chirality Memory Stored in Magnetic Domain Walls in the Ferromagnetic State of MnP. Phys Rev Lett 2021; 126:177205. [PMID: 33988392 DOI: 10.1103/physrevlett.126.177205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 04/08/2021] [Indexed: 06/12/2023]
Abstract
Chirality in a helimagnetic structure is determined by the sense of magnetic moment rotation. We found that the chiral information did not disappear even after the phase transition to the high-temperature ferromagnetic phase in a helimagnet MnP. The 2nd harmonic resistivity ρ^{2f}, which reflects the breaking down of mirror symmetry, was found to be almost unchanged after heating the sample above the ferromagnetic transition temperature and cooling it back to the helimagnetic state. The application of a magnetic field along the easy axis in the ferromagnetic state quenched the chirality-induced ρ^{2f}. This indicates that the chirality memory effect originated from the ferromagnetic domain walls.
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Affiliation(s)
- N Jiang
- Department of Basic Science, The University of Tokyo, Tokyo 153-8902, Japan
| | - Y Nii
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi 332-0012, Japan
| | - H Arisawa
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - E Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - J Ohe
- Department of Physics, Toho University, 2-2-1 Miyama, Funabashi 274-8510, Japan
| | - Y Onose
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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13
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Lee WY, Kang MS, Kim GS, Park NW, Choi KY, Le CT, Rashid MU, Saitoh E, Kim YS, Lee SK. Role of Ferromagnetic Monolayer WSe 2 Flakes in the Pt/Y 3Fe 5O 12 Bilayer Structure in the Longitudinal Spin Seebeck Effect. ACS Appl Mater Interfaces 2021; 13:15783-15790. [PMID: 33769783 DOI: 10.1021/acsami.0c22345] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The spin Seebeck effect (SSE) has attracted renewed interest as a promising phenomenon for energy harvesting systems. A noteworthy effort has been devoted to improving the SSE voltage by inserting ultrathin magnetic layers including Fe70Cu30 interlayers in Pt/Y3Fe5O12 (Pt/YIG) systems with increased spin-mixing conductance at the interfaces. Nevertheless, the responsible underlying physics associated with the role of the interlayer in Pt/YIG systems in the SSE is still unknown. In this paper, we demonstrate that with a monolayer tungsten diselenide (ML WSe2) interlayer in the Pt/YIG bilayer system, the longitudinal SSE (LSSE) voltage is significantly increased by the increased spin accumulation in the Pt layer; the spin fluctuation in ML WSe2 amplifies the spin current transmission because the in-plane-aligned WSe2 spins are coupled to thermally pumped spins under nonequilibrium magnetization conditions in the LSSE configuration at room temperature. The thermopower (VLSSE/ΔT) improves by 323% with respect to the value of the reference Pt/YIG bilayer sample in the LSSE at room temperature. In addition, the induced ferromagnetic properties of the ML WSe2 flakes on YIG increase the LSSE voltage (VLSSE) of the sample; the ferromagnetic properties are a result of the improved magnetic moment density in the ML WSe2 flakes and their two-dimensional (2D) ML nature in the LSSE under nonequilibrium magnetization conditions. The results can extend the application range of the materials in energy harvesting and provide important information on the physics of the LSSE with a transition metal dichalcogenide intermediate layer in spin transport.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Kwang-Yong Choi
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Chinh Tam Le
- Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Mamoon Ur Rashid
- Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Yong Soo Kim
- Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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14
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Meer H, Schreiber F, Schmitt C, Ramos R, Saitoh E, Gomonay O, Sinova J, Baldrati L, Kläui M. Direct Imaging of Current-Induced Antiferromagnetic Switching Revealing a Pure Thermomagnetoelastic Switching Mechanism in NiO. Nano Lett 2021; 21:114-119. [PMID: 33306407 DOI: 10.1021/acs.nanolett.0c03367] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We unravel the origin of current-induced magnetic switching of insulating antiferromagnet/heavy metal systems. We utilize concurrent transport and magneto-optical measurements to image the switching of antiferromagnetic domains in specially engineered devices of NiO/Pt bilayers. Different electrical pulsing and device geometries reveal different final states of the switching with respect to the current direction. We can explain these through simulations of the temperature-induced strain, and we identify the thermomagnetoelastic switching mechanism combined with thermal excitations as the origin, in which the final state is defined by the strain distributions and heat is required to switch the antiferromagnetic domains. We show that such a potentially very versatile noncontact mechanism can explain the previously reported contradicting observations of the switching final state, which were attributed to spin-orbit torque mechanisms.
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Affiliation(s)
- Hendrik Meer
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Felix Schreiber
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Christin Schmitt
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Rafael Ramos
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Centro de Investigación en Química Biolóxica e Materiais Moleculares (CIQUS), Departamento de Química-Física, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
| | - Eiji Saitoh
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Olena Gomonay
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Jairo Sinova
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Institut of Physics, Academy of Sciences of the Czech Republic, Praha 11720, Czech Republic
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - Lorenzo Baldrati
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - Mathias Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
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15
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Lee WY, Park NW, Kim GS, Kang MS, Choi JW, Choi KY, Jang HW, Saitoh E, Lee SK. Enhanced Spin Seebeck Thermopower in Pt/Holey MoS 2/Y 3Fe 5O 12 Hybrid Structure. Nano Lett 2021; 21:189-196. [PMID: 33274946 DOI: 10.1021/acs.nanolett.0c03499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We first observed the spin-to-charge conversion due to both the inverse Rashba-Edelstein effect (IREE) and inverse spin-Hall effect in a holey multilayer molybdenum disulfide (MoS2) intermediate layer in a Pt/YIG structure via LSSE measurements under nonequilibrium magnetization. We found an enhancement of approximately 238%, 307%, and 290% in the longitudinal spin Seebeck effect (LSSE) voltage, spin-to-charge current, and thermoelectric (TE) power factor, respectively, compared with the monolayer MoS2 interlayer in a Pt/YIG structure. Such an enhancement in the LSSE performance of Pt/holey MoS2/YIG can be explained by the improvement of spin accumulation in the Pt layer by induced spin fluctuation as well as increased additional spin-to-charge conversion due to in-plane IREE. Our findings represent a significant achievement in the understanding of spin transport in atomically thin MoS2 interlayers and pave the way toward large-area TE energy-harvesting devices in two-dimensional transition metal dichalcogenide materials.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Jae Won Choi
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Kwang-Yong Choi
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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16
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Baldrati L, Schmitt C, Gomonay O, Lebrun R, Ramos R, Saitoh E, Sinova J, Kläui M. Efficient Spin Torques in Antiferromagnetic CoO/Pt Quantified by Comparing Field- and Current-Induced Switching. Phys Rev Lett 2020; 125:077201. [PMID: 32857543 DOI: 10.1103/physrevlett.125.077201] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 07/02/2020] [Accepted: 07/10/2020] [Indexed: 06/11/2023]
Abstract
We achieve current-induced switching in collinear insulating antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is measured electrically by spin Hall magnetoresistance and confirmed by the magnetic field-induced spin-flop transition of the CoO layer. By applying current pulses and magnetic fields, we quantify the efficiency of the acting current-induced torques and estimate a current-field equivalence ratio of 4×10^{-11} T A^{-1} m^{2}. The Néel vector final state (n⊥j) is in line with a thermomagnetoelastic switching mechanism for a negative magnetoelastic constant of the CoO.
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Affiliation(s)
- L Baldrati
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - C Schmitt
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - O Gomonay
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - R Lebrun
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Unité Mixte de Physique CNRS, Thales, Université Paris-Sud, Université Paris-Saclay, Palaiseau 91767, France
| | - R Ramos
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - E Saitoh
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - J Sinova
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Institute of Physics, Academy of Sciences of the Czech Republic, Praha 11720, Czech Republic
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - M Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
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17
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Nambu Y, Barker J, Okino Y, Kikkawa T, Shiomi Y, Enderle M, Weber T, Winn B, Graves-Brook M, Tranquada JM, Ziman T, Fujita M, Bauer GEW, Saitoh E, Kakurai K. Observation of Magnon Polarization. Phys Rev Lett 2020; 125:027201. [PMID: 32701305 DOI: 10.1103/physrevlett.125.027201] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
We measure the mode-resolved direction of the precessional motion of the magnetic order, i.e., magnon polarization, via the chiral term of inelastic polarized neutron scattering spectra. The magnon polarization is a unique and unambiguous signature of magnets and is important in spintronics, affecting thermodynamic properties such as the magnitude and sign of the spin Seebeck effect. However, it has never been directly measured in any material until this work. The observation of both signs of magnon polarization in Y_{3}Fe_{5}O_{12} also gives direct proof of its ferrimagnetic nature. The experiments agree very well with atomistic simulations of the scattering cross section.
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Affiliation(s)
- Y Nambu
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - J Barker
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Y Okino
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - T Kikkawa
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI-AIMR, Tohoku University, Sendai 980-8577, Japan
| | - Y Shiomi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - M Enderle
- Institut Laue-Langevin (ILL), 38042 Grenoble, France
| | - T Weber
- Institut Laue-Langevin (ILL), 38042 Grenoble, France
| | - B Winn
- Oak Ridge National Lab (ORNL), Oak Ridge, Tennessee 37831, USA
| | - M Graves-Brook
- Oak Ridge National Lab (ORNL), Oak Ridge, Tennessee 37831, USA
| | - J M Tranquada
- Brookhaven National Lab (BNL), Upton, New York 11973-5000, USA
| | - T Ziman
- Institut Laue-Langevin (ILL), 38042 Grenoble, France
- Université Grenoble Alpes, CNRS, LPMMC, 38000 Grenoble, France
| | - M Fujita
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - G E W Bauer
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI-AIMR, Tohoku University, Sendai 980-8577, Japan
- Zernike Institute for Advanced Materials, University of Groningen, 9747 AG Groningen, Netherlands
| | - E Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI-AIMR, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
| | - K Kakurai
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Saitama 351-0198, Japan
- Materials Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
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18
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Lee WY, Park NW, Kang MS, Kim GS, Jang HW, Saitoh E, Lee SK. Surface Coverage Dependence of Spin-to-Charge Current across Pt/MoS 2/Y 3Fe 5O 12 Layers via Longitudinal Spin Seebeck Effect. J Phys Chem Lett 2020; 11:5338-5344. [PMID: 32558573 DOI: 10.1021/acs.jpclett.0c01502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The voltage induced by the inverse spin Hall effect (ISHE) is affected by several factors, including the spin Hall angle of the normal metal (NM), the quality and magnetic properties of the ferromagnetic material (FM), and the interface conditions between the NM and FM bilayers in longitudinal spin Seebeck effect (LSSE) measurement. Specifically, the interface conditions in NM/FM systems via LSSE devices play a crucial role in determining the efficiency of spin current injection into the NM layer. In this letter, we report a new approach to controlling the efficiency of spin current injection into a Pt layer across a Pt/Y3Fe5O12 (YIG) interface by surface coverage of the intermediate layer. A continuous, large-area multilayer molybdenum dichalcogenide (MoS2) thin film grown by chemical vapor deposition is inserted between the Pt and YIG layers in the LSSE configuration. We found that, when the large-area multilayer MoS2 film was present, the measured ISHE-induced voltage and theoretically calculated spin current in the Pt/MoS2/YIG trilayer increased by ∼510% and 470%, respectively, compared to those of a Pt/YIG bilayer. The induced voltage and spin current were very sensitive to the surface conductance, which was affected by the surface coverage of the multilayer MoS2 films in the LSSE measurement. Furthermore, the theoretically calculated spin current and spin mixing conductance in the trilayer geometry are in qualitatively good agreement with the experimental observations. These measurements enable us to explain the effect of the interface conditions on the spin Seebeck effect in spin transport.
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Affiliation(s)
- Won-Yong Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - No-Won Park
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Min-Sung Kang
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Gil-Sung Kim
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Sang-Kwon Lee
- Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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19
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Takahashi R, Chudo H, Matsuo M, Harii K, Ohnuma Y, Maekawa S, Saitoh E. Giant spin hydrodynamic generation in laminar flow. Nat Commun 2020; 11:3009. [PMID: 32541678 PMCID: PMC7295809 DOI: 10.1038/s41467-020-16753-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 05/20/2020] [Indexed: 11/18/2022] Open
Abstract
Hydrodynamic motion can generate a flux of electron-spin’s angular momentum via the coupling between fluid rotation and electron spins. Such hydrodynamic generation, called spin hydrodynamic generation (SHDG), has recently attracted attention in a wide range of fields, especially in spintronics. Spintronics deals with spin-mediated interconversion taking place on a micro or nano scale because of the spin-diffusion length scale. To be fully incorporated into the interconversion, SHDG physics should also be established in such a minute scale, where most fluids exhibit a laminar flow. Here, we report electric voltage generation due to the SHDG in a laminar flow of a liquid-metal mercury. The experimental results show a scaling rule unique to the laminar-flow SHDG. Furthermore, its energy conversion efficiency turns out to be about 105 greater than of the turbulent one. Our findings reveal that the laminar-flow SHDG is suitable to downsizing and to extend the coverage of fluid spintronics. In spin hydrodynamic generation originating from the coupling of mechanical rotation in a fluid and electron spin, fluid vorticity can be converted into an electric voltage via a spin current. Here, the authors demonstrate experimentally that the energy conversion in a laminar flow regime is strongly enhanced over the turbulent regime.
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Affiliation(s)
- R Takahashi
- Natural Science Division, Faculty of Core Research, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo, 112-8610, Japan. .,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan. .,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan.
| | - H Chudo
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan
| | - M Matsuo
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan.,Advanced Institute for Material Research, Tohoku University, Sendai, 980-8577, Japan.,Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China.,CAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, 100190, China.,Riken Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - K Harii
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan.,Department of Advanced Functional Materials Research, National Institutes for Quantum and Radiological Science and Technology, Takasaki, Gunma, 370-1292, Japan
| | - Y Ohnuma
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan.,Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China
| | - S Maekawa
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan.,Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China.,Riken Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - E Saitoh
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan.,Advanced Institute for Material Research, Tohoku University, Sendai, 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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20
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Chen Y, Shiomi Y, Qiu Z, Niizeki T, Umeda M, Saitoh E. Electric readout of magnetic stripes in insulators. Sci Rep 2019; 9:19052. [PMID: 31836771 PMCID: PMC6911107 DOI: 10.1038/s41598-019-55565-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 11/30/2019] [Indexed: 11/09/2022] Open
Abstract
In superconductors, a topological configuration of the superconducting order parameter called a superconducting vortex carries magnetization. Such a magnetic topological object behaves like a minute particle generating a magnetic flux. Since the flux is localized with a nanometer scale, the vortex provides a nano-scale probe for local magnetic fields. Here we show that information of magnetic stripes in insulators can be read out by using vortices in an adjacent superconductor film as a probe. The orientation and width of magnetic micro stripes are both transcribed into resistance change of the superconductor through the modulation of vortex mobility affected by local magnetization. By changing the direction of external magnetic fields, zero-field resistance changes continuously according to the stripe orientation, and its modulation magnitude reaches up to 100%. The width of the stripes can also be estimated from the oscillatory magnetoresistance. Our results demonstrate a new possibility for non-volatile analog memory devices based on topological objects.
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Affiliation(s)
- Yao Chen
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.
| | - Yuki Shiomi
- Department of Basic Science, The University of Tokyo, Meguro, Tokyo, 153-8902, Japan
| | - Zhiyong Qiu
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Materials Science and Engineering, Dalian University of Technology, Dalian, 116024, China
| | - Tomohiko Niizeki
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Maki Umeda
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
- Department of Applied Physics, University of Tokyo, Hongo, Tokyo, 113-8656, Japan
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21
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Wen Z, Qiu Z, Tölle S, Gorini C, Seki T, Hou D, Kubota T, Eckern U, Saitoh E, Takanashi K. Spin-charge conversion in NiMnSb Heusler alloy films. Sci Adv 2019; 5:eaaw9337. [PMID: 31853493 PMCID: PMC6910839 DOI: 10.1126/sciadv.aaw9337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 10/28/2019] [Indexed: 06/10/2023]
Abstract
Half-metallic Heusler alloys are attracting considerable attention because of their unique half-metallic band structures, which exhibit high spin polarization and yield huge magnetoresistance ratios. Besides serving as ferromagnetic electrodes, Heusler alloys also have the potential to host spin-charge conversion. Here, we report on the spin-charge conversion effect in the prototypical Heusler alloy NiMnSb. An unusual charge signal was observed with a sign change at low temperature, which can be manipulated by film thickness and ordering structure. It is found that the spin-charge conversion has two contributions. First, the interfacial contribution causes a negative voltage signal, which is almost constant versus temperature. The second contribution is temperature dependent because it is dominated by minority states due to thermally excited magnons in the bulk part of the film. This work provides a pathway for the manipulation of spin-charge conversion in ferromagnetic metals by interface-bulk engineering for spintronic devices.
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Affiliation(s)
- Zhenchao Wen
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- National Institute for Materials Science (NIMS), Tsukuba 304-0047, Japan
| | - Zhiyong Qiu
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Materials Science and Engineering, Dalian University of Technology, Dalian, China
| | - Sebastian Tölle
- Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
| | - Cosimo Gorini
- Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany
| | - Takeshi Seki
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Dazhi Hou
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Takahide Kubota
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Ulrich Eckern
- Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Koki Takanashi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Center for Science and Innovation in Spintronics, Core Research Cluster, Tohoku University, Sendai 980-8577, Japan
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22
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Ramos R, Hioki T, Hashimoto Y, Kikkawa T, Frey P, Kreil AJE, Vasyuchka VI, Serga AA, Hillebrands B, Saitoh E. Room temperature and low-field resonant enhancement of spin Seebeck effect in partially compensated magnets. Nat Commun 2019; 10:5162. [PMID: 31727884 PMCID: PMC6856150 DOI: 10.1038/s41467-019-13121-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 10/08/2019] [Indexed: 11/09/2022] Open
Abstract
Resonant enhancement of spin Seebeck effect (SSE) due to phonons was recently discovered in Y[Formula: see text]Fe[Formula: see text]O[Formula: see text] (YIG). This effect is explained by hybridization between the magnon and phonon dispersions. However, this effect was observed at low temperatures and high magnetic fields, limiting the scope for applications. Here we report observation of phonon-resonant enhancement of SSE at room temperature and low magnetic field. We observe in Lu[Formula: see text]BiFe[Formula: see text]GaO[Formula: see text] an enhancement 700% greater than that in a YIG film and at very low magnetic fields around 10[Formula: see text] T, almost one order of magnitude lower than that of YIG. The result can be explained by the change in the magnon dispersion induced by magnetic compensation due to the presence of non-magnetic ion substitutions. Our study provides a way to tune the magnon response in a crystal by chemical doping, with potential applications for spintronic devices.
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Affiliation(s)
- R Ramos
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.
| | - T Hioki
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Y Hashimoto
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - T Kikkawa
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - P Frey
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - A J E Kreil
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - V I Vasyuchka
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - A A Serga
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - B Hillebrands
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663, Kaiserslautern, Germany
| | - E Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
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23
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Baldrati L, Gomonay O, Ross A, Filianina M, Lebrun R, Ramos R, Leveille C, Fuhrmann F, Forrest TR, Maccherozzi F, Valencia S, Kronast F, Saitoh E, Sinova J, Kläui M. Mechanism of Néel Order Switching in Antiferromagnetic Thin Films Revealed by Magnetotransport and Direct Imaging. Phys Rev Lett 2019; 123:177201. [PMID: 31702247 DOI: 10.1103/physrevlett.123.177201] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 08/07/2019] [Indexed: 06/10/2023]
Abstract
We probe the current-induced magnetic switching of insulating antiferromagnet-heavy-metal systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe switching of more than one-third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely, the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.
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Affiliation(s)
- L Baldrati
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - O Gomonay
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - A Ross
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - M Filianina
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - R Lebrun
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - R Ramos
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - C Leveille
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - F Fuhrmann
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - T R Forrest
- Diamond Light Source, Chilton, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - F Maccherozzi
- Diamond Light Source, Chilton, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - S Valencia
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - F Kronast
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany
| | - E Saitoh
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - J Sinova
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
| | - M Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
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24
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Oyanagi K, Takahashi S, Cornelissen LJ, Shan J, Daimon S, Kikkawa T, Bauer GEW, van Wees BJ, Saitoh E. Spin transport in insulators without exchange stiffness. Nat Commun 2019; 10:4740. [PMID: 31628333 PMCID: PMC6800424 DOI: 10.1038/s41467-019-12749-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 09/25/2019] [Indexed: 11/24/2022] Open
Abstract
The discovery of new materials that efficiently transmit spin currents has been important for spintronics and material science. The electric insulator Gd3Ga5O12 (GGG), a standard substrate for growing magnetic films, can be a spin current generator, but has never been considered as a superior conduit for spin currents. Here we report spin current propagation in paramagnetic GGG over several microns. Surprisingly, spin transport persists up to temperatures of 100 K \documentclass[12pt]{minimal}
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\usepackage{amssymb}
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\begin{document}$$\gg$$\end{document}≫Tg = 180 mK, the magnetic glass-like transition temperature of GGG. At 5 K and 3.5 T, we find a spin diffusion length λGGG = 1.8 ± 0.2 μm and a spin conductivity σGGG = (7.3 ± 0.3) × 104 Sm−1 that is larger than that of the record quality magnet Y3Fe5O12 (YIG). We conclude that exchange stiffness is not required for efficient spin transport, which challenges conventional models and provides new material-design strategies for spintronic devices. Long-range spin transport is essential for spintronics applications, but so far has only been achieved in magnets below their Curie temperature. Here, the authors report on efficient spin transport in paramagnetic insulator Gd3Ga5O12 exposed to a moderate magnetic field exhibiting a spin diffusion length of 1.8 μm.
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Affiliation(s)
- Koichi Oyanagi
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.
| | - Saburo Takahashi
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan
| | - Ludo J Cornelissen
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Juan Shan
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Shunsuke Daimon
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan
| | - Takashi Kikkawa
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Gerrit E W Bauer
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Bart J van Wees
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Department of Applied Physics, The University of Tokyo, Tokyo, 113-8656, Japan.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
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25
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Hirobe D, Sato M, Hagihala M, Shiomi Y, Masuda T, Saitoh E. Magnon Pairs and Spin-Nematic Correlation in the Spin Seebeck Effect. Phys Rev Lett 2019; 123:117202. [PMID: 31573271 DOI: 10.1103/physrevlett.123.117202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Indexed: 06/10/2023]
Abstract
Investigating exotic magnetic materials with spintronic techniques is effective at advancing magnetism as well as spintronics. In this work, we report unusual field-induced suppression of the spin Seebeck effect (SSE) in a quasi-one-dimensional frustrated spin-1/2 magnet LiCuVO_{4}, known to exhibit spin-nematic correlation in a wide range of external magnetic field B. The suppression takes place above |B|≳2 T in spite of the B-linear isothermal magnetization curves in the same B range. The result can be attributed to the growth of the spin-nematic correlation while increasing B. The correlation stabilizes magnon pairs carrying spin 2, thereby suppressing the interfacial spin injection of SSE by preventing the spin-1 exchange between single magnons and conduction electrons at the interface. This interpretation is supported by integrating thermodynamic measurements and theoretical analysis on the SSE.
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Affiliation(s)
- Daichi Hirobe
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Masahiro Sato
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
- Department of Physics, Ibaraki University, Mito, Ibaraki 310-8512, Japan
| | - Masato Hagihala
- Institute of Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581 Japan
- Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tokai, Ibaraki 319-1106, Japan
| | - Yuki Shiomi
- Department of Basic Science, University of Tokyo, Meguro, Tokyo 153-8902, Japan
| | - Takatsugu Masuda
- Institute of Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581 Japan
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
- The Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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26
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Park NW, Kang DY, Lee WY, Yoon YS, Kim GS, Saitoh E, Kim TG, Lee SK. Controllable Seebeck Coefficients of a Metal-Diffused Aluminum Oxide Layer via Conducting Filament Density and Energy Filtering. ACS Appl Mater Interfaces 2019; 11:23303-23312. [PMID: 31184861 DOI: 10.1021/acsami.9b01289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We investigate the intrinsic thermoelectric (TE) properties of the metal-diffused aluminum oxide (AO) layer in metal/AO/metal structures, where the metallic conducting filaments (CFs) were locally formed in the structures via an electrical breakdown (EBD) process as shown by resistive switching memory devices, by directly measuring cross-plane Seebeck coefficients on the CF-containing insulating AO layers. The results showed that the Seebeck coefficients of the CF-containing AO layer in metal/AO/metal structures were influenced by the generation of the metallic CFs, which is due to the diffusion of the metal into the insulating AO layers when exposed to a temperature gradient in the direction of the cross plane of the sample. In addition, the increase in the Seebeck coefficients of the CF-containing AO layer when the number of EBD-processed patterns was increased is satisfactorily explained by the low-energy carrier (i.e., minority carriers) filtering through the metal-oxide interfacial barriers in the metal/AO/metal structures.
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Affiliation(s)
- No-Won Park
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Dae Yun Kang
- School of Electrical Engineering , Korea University , Seoul 02841 , Republic of Korea
| | - Won-Yong Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Yo-Seop Yoon
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Gil-Sung Kim
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Eiji Saitoh
- Institute for Materials Research , Tohoku University , Sendai 980-8577 , Japan
- WPI Advanced Institute for Materials Research , Tohoku University , Sendai 980-8577 , Japan
- Department of Applied Physics , The University of Tokyo , Tokyo 113-8656 , Japan
| | - Tae Geun Kim
- School of Electrical Engineering , Korea University , Seoul 02841 , Republic of Korea
| | - Sang-Kwon Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
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27
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Yamamoto K, Thiang GC, Pirro P, Kim KW, Everschor-Sitte K, Saitoh E. Topological Characterization of Classical Waves: The Topological Origin of Magnetostatic Surface Spin Waves. Phys Rev Lett 2019; 122:217201. [PMID: 31283306 DOI: 10.1103/physrevlett.122.217201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Indexed: 06/09/2023]
Abstract
We propose a topological characterization of Hamiltonians describing classical waves. Applying it to the magnetostatic surface spin waves that are important in spintronics applications, we settle the speculation over their topological origin. For a class of classical systems that includes spin waves driven by dipole-dipole interactions, we show that the topology is characterized by vortex lines in the Brillouin zone in such a way that the symplectic structure of Hamiltonian mechanics plays an essential role. We define winding numbers around these vortex lines and identify them to be the bulk topological invariants for a class of semimetals. Exploiting the bulk-edge correspondence appropriately reformulated for these classical waves, we predict that surface modes appear but not in a gap of the bulk frequency spectrum. This feature, consistent with the magnetostatic surface spin waves, indicates a broader realm of topological phases of matter beyond spectrally gapped ones.
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Affiliation(s)
- Kei Yamamoto
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Institut für Physik, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany
| | - Guo Chuan Thiang
- School of Mathematical Sciences, University of Adelaide, SA 5000, Australia
| | - Philipp Pirro
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Kyoung-Whan Kim
- Institut für Physik, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany
- Center for Spintronics, Korea Institute of Science and Technology, Seoul 02792, Korea
| | | | - Eiji Saitoh
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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28
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Iwasaki Y, Takeuchi I, Stanev V, Kusne AG, Ishida M, Kirihara A, Ihara K, Sawada R, Terashima K, Someya H, Uchida KI, Saitoh E, Yorozu S. Machine-learning guided discovery of a new thermoelectric material. Sci Rep 2019; 9:2751. [PMID: 30808974 PMCID: PMC6391459 DOI: 10.1038/s41598-019-39278-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 01/22/2019] [Indexed: 11/10/2022] Open
Abstract
Thermoelectric technologies are becoming indispensable in the quest for a sustainable future. Recently, an emerging phenomenon, the spin-driven thermoelectric effect (STE), has garnered much attention as a promising path towards low cost and versatile thermoelectric technology with easily scalable manufacturing. However, progress in development of STE devices is hindered by the lack of understanding of the fundamental physics and materials properties responsible for the effect. In such nascent scientific field, data-driven approaches relying on statistics and machine learning, instead of more traditional modeling methods, can exhibit their full potential. Here, we use machine learning modeling to establish the key physical parameters controlling STE. Guided by the models, we have carried out actual material synthesis which led to the identification of a novel STE material with a thermopower an order of magnitude larger than that of the current generation of STE devices.
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Affiliation(s)
- Yuma Iwasaki
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan. .,PRESTO, JST, Saitama, 322-0012, Japan.
| | - Ichiro Takeuchi
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA.,Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD, 20742, USA
| | - Valentin Stanev
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA.,Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD, 20742, USA
| | - Aaron Gilad Kusne
- Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA.,National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Masahiko Ishida
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Akihiro Kirihara
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Kazuki Ihara
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Ryohto Sawada
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Koichi Terashima
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Hiroko Someya
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Ken-Ichi Uchida
- PRESTO, JST, Saitama, 322-0012, Japan.,Research Center for Magnetic and Spintronic Materials (CMSM), National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan.,Research and Services Division of Materials Data and Integrated System (MaDIS), National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan.,Institute for Materials Research, Tohoku University, Sendai, 908-8577, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai, 908-8577, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Institute for Materials Research, Tohoku University, Sendai, 908-8577, Japan.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
| | - Shinichi Yorozu
- Central Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
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29
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Park NW, Lee WY, Yoon YS, Ahn JY, Lee JH, Kim GS, Kim TG, Choi CJ, Park JS, Saitoh E, Lee SK. Direct Probing of Cross-Plane Thermal Properties of Atomic Layer Deposition Al 2O 3/ZnO Superlattice Films with an Improved Figure of Merit and Their Cross-Plane Thermoelectric Generating Performance. ACS Appl Mater Interfaces 2018; 10:44472-44482. [PMID: 30507128 DOI: 10.1021/acsami.8b15997] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
There is a recent interest in semiconducting superlattice films because their low dimensionality can increase the thermal power and phonon scattering at the interface in superlattice films. However, experimental studies in all cross-plane thermoelectric (TE) properties, including thermal conductivity, Seebeck coefficient, and electrical conductivity, have not been performed from these semiconducting superlattice films because of substantial difficulties in the direct measurement of the Seebeck coefficient and electrical conductivity. Unlike the conventional measurement method, we present a technique using a structure of sandwiched superlattice films between two embedded heaters as the heating source, and electrodes with two Cu plates, which directly enables the investigation of the Seebeck coefficient and electrical conductivity across the Al2O3/ZnO superlattice films, prepared by the atomic layer deposition method. Used in combination with the promising cross-plane four-point probe 3-ω method, our measurements and analysis demonstrate all cross-plane TE properties of Al2O3/ZnO superlattice films in the temperature range of 80 to 500 K. Our experimental methodology and the obtained results represent a significant advancement in the understanding of phonons and electrical transports in nanostructured materials, especially in semiconducting superlattice films in various temperature ranges.
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Affiliation(s)
- No-Won Park
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Won-Yong Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Yo-Seop Yoon
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Jay-Young Ahn
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Jung-Hoon Lee
- Division of Materials Science and Engineering , Hanyang University , Seoul 04763 , Republic of Korea
| | - Gil-Sung Kim
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Tae Geun Kim
- School of Electrical Engineering , Korea University , Seoul 02841 , Republic of Korea
| | - Chel-Jong Choi
- Department of Semiconductor Science and Technology , Chonbuk National University , Jeonju 54896 , Republic of Korea
| | - Jin-Seong Park
- Division of Materials Science and Engineering , Hanyang University , Seoul 04763 , Republic of Korea
| | | | - Sang-Kwon Lee
- Department of Physics , Chung-Ang University , Seoul 06974 , Republic of Korea
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30
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Ogawa M, Kagaya H, Shibata S, Inamoto Y, Aoyagi Y, Onogi K, Mori S, Akahori R, Saitoh E. Swallowing rounds in patients with dysphagia. Ann Phys Rehabil Med 2018. [DOI: 10.1016/j.rehab.2018.05.1056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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31
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Kagaya H, Ogawa M, Mori S, Aoyagi Y, Shibata S, Onogi K, Inamoto Y, Mori H, Saitoh E. Development of peripheral magnetic stimulation system to stimulate suprahyoid muscles. Ann Phys Rehabil Med 2018. [DOI: 10.1016/j.rehab.2018.05.812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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32
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Aoyagi Y, Taniguchi H, Imaeda S, Hirumuta M, Kagaya H, Saitoh E. Elicitation of swallowing reflex by esophageal stimulation in healthy subjects – Evaluation using high resolution manometry. Ann Phys Rehabil Med 2018. [DOI: 10.1016/j.rehab.2018.05.980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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33
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Hirano S, Saitoh E, Kagaya H, Sonoda S, Mukaino M, Tsunoda T, Tanabe S, Yamada J, Suzuki A, Konosu H. Welwalk facilitate early improvement in walking independence of stroke patients with hemiplegia. Ann Phys Rehabil Med 2018. [DOI: 10.1016/j.rehab.2018.05.199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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34
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Mizokoshi E, Kagaya H, Aoyagi Y, Shibata S, Onogi K, Inamoto Y, Pongpipatpaiboon K, Saitoh E. Factors affecting aspiration in chew-swallow and discrete swallow in stroke patients. Ann Phys Rehabil Med 2018. [DOI: 10.1016/j.rehab.2018.05.420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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35
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Qiu Z, Hou D, Barker J, Yamamoto K, Gomonay O, Saitoh E. Spin colossal magnetoresistance in an antiferromagnetic insulator. Nat Mater 2018; 17:577-580. [PMID: 29807985 DOI: 10.1038/s41563-018-0087-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 04/24/2018] [Indexed: 06/08/2023]
Abstract
Colossal magnetoresistance (CMR) refers to a large change in electrical conductivity induced by a magnetic field in the vicinity of a metal-insulator transition and has inspired extensive studies for decades1,2. Here we demonstrate an analogous spin effect near the Néel temperature, TN = 296 K, of the antiferromagnetic insulator Cr2O3. Using a yttrium iron garnet YIG/Cr2O3/Pt trilayer, we injected a spin current from the YIG into the Cr2O3 layer and collected, via the inverse spin Hall effect, the spin signal transmitted into the heavy metal Pt. We observed a two orders of magnitude difference in the transmitted spin current within 14 K of the Néel temperature. This transition between spin conducting and non-conducting states was also modulated by a magnetic field in isothermal conditions. This effect, which we term spin colossal magnetoresistance (SCMR), has the potential to simplify the design of fundamental spintronics components, for instance, by enabling the realization of spin-current switches or spin-current-based memories.
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Affiliation(s)
- Zhiyong Qiu
- Institute for Materials Research, Tohoku University, Sendai, Japan
- Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams (Ministry of Education), School of Materials Science and Engineering, Dalian University of Technology, Dalian, China
| | - Dazhi Hou
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan.
| | - Joseph Barker
- Institute for Materials Research, Tohoku University, Sendai, Japan
| | - Kei Yamamoto
- Institute for Materials Research, Tohoku University, Sendai, Japan
- Institut für Physik, Johannes Gutenberg Universität Mainz, Mainz, Germany
- Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL, USA
- Centre of Materials for Information Technology, University of Alabama, Tuscaloosa, AL, USA
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan
| | - Olena Gomonay
- Institut für Physik, Johannes Gutenberg Universität Mainz, Mainz, Germany
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan
- Department of applied physics, University of Tokyo, Tokyo, Japan
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36
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Cramer J, Fuhrmann F, Ritzmann U, Gall V, Niizeki T, Ramos R, Qiu Z, Hou D, Kikkawa T, Sinova J, Nowak U, Saitoh E, Kläui M. Magnon detection using a ferroic collinear multilayer spin valve. Nat Commun 2018. [PMID: 29540718 PMCID: PMC5852167 DOI: 10.1038/s41467-018-03485-5] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Information transport and processing by pure magnonic spin currents in insulators is a promising alternative to conventional charge-current-driven spintronic devices. The absence of Joule heating and reduced spin wave damping in insulating ferromagnets have been suggested for implementing efficient logic devices. After the successful demonstration of a majority gate based on the superposition of spin waves, further components are required to perform complex logic operations. Here, we report on magnetization orientation-dependent spin current detection signals in collinear magnetic multilayers inspired by the functionality of a conventional spin valve. In Y3Fe5O12|CoO|Co, we find that the detection amplitude of spin currents emitted by ferromagnetic resonance spin pumping depends on the relative alignment of the Y3Fe5O12 and Co magnetization. This yields a spin valve-like behavior with an amplitude change of 120% in our systems. We demonstrate the reliability of the effect and identify its origin by both temperature-dependent and power-dependent measurements.
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Affiliation(s)
- Joel Cramer
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany.,Graduate School of Excellence Materials Science in Mainz, 55128, Mainz, Germany
| | - Felix Fuhrmann
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Ulrike Ritzmann
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany.,Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Vanessa Gall
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Tomohiko Niizeki
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Rafael Ramos
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Zhiyong Qiu
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,School of Materials Science and Engineering, Dalian University of Technology, Dalian, 116024, China
| | - Dazhi Hou
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Takashi Kikkawa
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - Jairo Sinova
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Ulrich Nowak
- Department of Physics, University of Konstanz, 78457, Konstanz, Germany
| | - Eiji Saitoh
- Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
| | - Mathias Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany. .,Graduate School of Excellence Materials Science in Mainz, 55128, Mainz, Germany.
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37
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Taniguchi H, Aoyagi Y, Matsuo K, Nakagawa K, Saitoh E. Development of an oesophageal stimulation method to elicit swallowing reflex in humans. J Oral Rehabil 2017; 45:211-215. [PMID: 29247533 DOI: 10.1111/joor.12599] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2017] [Indexed: 12/16/2022]
Abstract
Swallowing reflex is known to be evoked by gastroesophageal regurgitation or oesophageal stimulation in animal studies. However, details regarding the stimulating material, bolus size and stimulation area remain unclear for the stimulation-induced type of swallowing reflex in humans. Here, we evaluated the effects of different kinds of stimulation via water and air injection of the oesophagus on the initiation of the swallowing reflex. Nine healthy individuals participated in this study. A fibre-optic endoscope was passed transnasally, and a thin catheter for injection was passed through the other side. The tip of the catheter was placed at the upper, upper middle, lower middle or lower region of the oesophagus, and the rate of injection was controlled at 0.2 mL/s. Swallowing reflex latency was calculated as the time from injection via air or thin/thick fluid until the onset of white-out in endoscopic images. Reflex latency was significantly shorter when injection occurred at the upper region of the oesophagus than at the lower region, for both thin and thick fluids (P < .01). At the upper region of the oesophagus, the latency was significantly shorter after injection of thin fluid than with thick fluid (P < .05). Injection of air did not induce the swallowing reflex at all sites. These findings suggest that while the swallowing reflex is evoked by stimulation via fluid injection of the oesophagus in humans, sensitivity is greatest in the upper region of the oesophagus compared with the lower region and can vary depending on the injecting material.
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Affiliation(s)
- H Taniguchi
- Department of Dentistry, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Y Aoyagi
- Department of Rehabilitation Medicine, School of Medicine, Fujita Health University, Toyoake, Japan
| | - K Matsuo
- Department of Dentistry, School of Medicine, Fujita Health University, Toyoake, Japan
| | - K Nakagawa
- Department of Dentistry, School of Medicine, Fujita Health University, Toyoake, Japan
| | - E Saitoh
- Department of Rehabilitation Medicine, School of Medicine, Fujita Health University, Toyoake, Japan
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38
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Shibata S, Inamoto Y, Saitoh E, Kagaya H, Aoyagi Y, Ota K, Akahori R, Fujii N, Palmer JB, González-Fernández M. The effect of bolus volume on laryngeal closure and UES opening in swallowing: Kinematic analysis using 320-row area detector CT study. J Oral Rehabil 2017; 44:974-981. [PMID: 28891595 DOI: 10.1111/joor.12573] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/06/2017] [Indexed: 01/09/2023]
Abstract
This study investigated the effects of three different volumes of honey-thick liquid on the temporal characteristics of swallowing. Twenty-six healthy subjects (15 males, 11 females) underwent 320-row area detector CT scan while swallowing 3, 10 and 20 mL of honey-thick liquid barium. Three-dimensional images were created at 10 images/s. Kinematic events involving six structures (velopharynx, hyoid bone, epiglottis, laryngeal vestibule (LV), true vocal cords (TVC), upper esophageal sphincter (UES)) and timing of bolus movement were timed using frame by frame analysis. The overall sequence of events did not differ across three volumes; however, increasing bolus volume significantly changed the onset and termination of events. The bolus head reached to pharynx and esophagus earlier and the duration of bolus passing through UES was significantly longer in 10 and 20 mL compared to 3 mL (P < .05). Consequently, the onset of UES opening was significantly earlier with increased volume (P < .05). LV and TVC closure occurred later in 20 mL compared to 3 mL (P < .05). These changes in motion of pharynx and larynx appeared to promote swallow safety by preventing aspiration, suggesting that anatomical structure movements adapt in response to bolus volume. Our findings also suggest that the pharyngeal swallow behaviours may be modified by afferents in the oral cavity. The three-dimensional visualization and quantitative measurements provided by 320-ADCT provide essential benchmarks for understanding swallowing, both normal and abnormal.
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Affiliation(s)
- S Shibata
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Y Inamoto
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan.,Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - E Saitoh
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - H Kagaya
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Y Aoyagi
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - K Ota
- Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - R Akahori
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - N Fujii
- Department of Radiology, School of Medicine, Fujita Health University, Toyoake, Japan
| | - J B Palmer
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University, Baltimore, MD, USA
| | - M González-Fernández
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University, Baltimore, MD, USA
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39
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Kobayashi D, Yoshikawa T, Matsuo M, Iguchi R, Maekawa S, Saitoh E, Nozaki Y. Spin Current Generation Using a Surface Acoustic Wave Generated via Spin-Rotation Coupling. Phys Rev Lett 2017; 119:077202. [PMID: 28949686 DOI: 10.1103/physrevlett.119.077202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Indexed: 06/07/2023]
Abstract
We demonstrate the generation of alternating spin current (SC) via spin-rotation coupling (SRC) using a surface acoustic wave (SAW) in a Cu film. Ferromagnetic resonance caused by injecting SAWs was observed in a Ni-Fe film attached to a Cu film, with the resonance further found to be suppressed through the insertion of a SiO_{2} film into the interface. The intensity of the resonance depended on the angle between the wave vector of the SAW and the magnetization of the Ni-Fe film. This angular dependence is explicable in terms of the presence of spin transfer torque from a SC generated via SRC.
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Affiliation(s)
- D Kobayashi
- Department of Physics, Keio University, Yokohama 223-8522, Japan
| | - T Yoshikawa
- Department of Physics, Keio University, Yokohama 223-8522, Japan
| | - M Matsuo
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - R Iguchi
- National Institute for Materials Science, Tsukuba 305-0047, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Maekawa
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
| | - E Saitoh
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
- Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Y Nozaki
- Department of Physics, Keio University, Yokohama 223-8522, Japan
- Center for Spintronics Research Network, Keio University, Yokohama 223-8522, Japan
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40
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Shiomi Y, Lustikova J, Saitoh E. Oscillatory Nernst effect in Pt|ferrite|cuprate-superconductor trilayer films. Sci Rep 2017; 7:5358. [PMID: 28706217 PMCID: PMC5509755 DOI: 10.1038/s41598-017-05747-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/26/2017] [Indexed: 11/25/2022] Open
Abstract
Although magnetism and superconductivity hardly coexist in a single material, recent advances in nanotechnology and spintronics have brought to light their interplay in magnetotransport in thin-film heterostructures. Here, we found a periodic oscillation of Nernst voltage with respect to magnetic fields in Pt|LiFe5O8 (Pt|LFO) bilayers grown on a cuprate superconductor YBa2Cu3O7−x (YBCO). At high temperatures above the superconducting transition temperature (TC) of YBCO, spin Seebeck voltages originating in Pt|LFO layers are observed. As temperature decreases well below TC, the spin Seebeck voltage is suppressed and unconventional periodic voltage oscillation as a function of magnetic fields appears; such an oscillation emerging along the Hall direction in the superconducting state has not been observed yet. Dynamics of superconducting vortices pinned by surface precipitates seems responsible for the oscillatory Nernst effect.
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Affiliation(s)
- Y Shiomi
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan. .,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Aoba-ku, Sendai, 980-8577, Japan.
| | - J Lustikova
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
| | - E Saitoh
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Aoba-ku, Sendai, 980-8577, Japan.,WPI Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
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41
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Hashimoto Y, Daimon S, Iguchi R, Oikawa Y, Shen K, Sato K, Bossini D, Tabuchi Y, Satoh T, Hillebrands B, Bauer GEW, Johansen TH, Kirilyuk A, Rasing T, Saitoh E. All-optical observation and reconstruction of spin wave dispersion. Nat Commun 2017; 8:15859. [PMID: 28604690 PMCID: PMC5477491 DOI: 10.1038/ncomms15859] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Accepted: 05/01/2017] [Indexed: 02/03/2023] Open
Abstract
To know the properties of a particle or a wave, one should measure how its energy changes with its momentum. The relation between them is called the dispersion relation, which encodes essential information of the kinetics. In a magnet, the wave motion of atomic spins serves as an elementary excitation, called a spin wave, and behaves like a fictitious particle. Although the dispersion relation of spin waves governs many of the magnetic properties, observation of their entire dispersion is one of the challenges today. Spin waves whose dispersion is dominated by magnetostatic interaction are called pure-magnetostatic waves, which are still missing despite of their practical importance. Here, we report observation of the band dispersion relation of pure-magnetostatic waves by developing a table-top all-optical spectroscopy named spin-wave tomography. The result unmasks characteristics of pure-magnetostatic waves. We also demonstrate time-resolved measurements, which reveal coherent energy transfer between spin waves and lattice vibrations.
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Affiliation(s)
- Yusuke Hashimoto
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Shunsuke Daimon
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Ryo Iguchi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Yasuyuki Oikawa
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Ka Shen
- Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, Delft 2628 CJ, The Netherlands
| | - Koji Sato
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Davide Bossini
- Institute for Photon Science and Technology, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yutaka Tabuchi
- Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8904, Japan
| | - Takuya Satoh
- Department of Physics, Kyushu University, Fukuoka 819-0395, Japan
| | - Burkard Hillebrands
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Gerrit E W Bauer
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.,Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, Delft 2628 CJ, The Netherlands
| | - Tom H Johansen
- Department of Physics, University of Oslo, Oslo 0316, Norway.,Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522, Australia
| | - Andrei Kirilyuk
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen 6525 AJ, The Netherlands
| | - Theo Rasing
- Radboud University Nijmegen, Institute for Molecules and Materials, Nijmegen 6525 AJ, The Netherlands
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
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42
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Hou D, Qiu Z, Barker J, Sato K, Yamamoto K, Vélez S, Gomez-Perez JM, Hueso LE, Casanova F, Saitoh E. Tunable Sign Change of Spin Hall Magnetoresistance in Pt/NiO/YIG Structures. Phys Rev Lett 2017; 118:147202. [PMID: 28430518 DOI: 10.1103/physrevlett.118.147202] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Indexed: 06/07/2023]
Abstract
Spin Hall magnetoresistance (SMR) has been investigated in Pt/NiO/YIG structures in a wide range of temperature and NiO thickness. The SMR shows a negative sign below a temperature that increases with the NiO thickness. This is contrary to a conventional SMR theory picture applied to the Pt/YIG bilayer, which always predicts a positive SMR. The negative SMR is found to persist even when NiO blocks the spin transmission between Pt and YIG, indicating it is governed by the spin current response of the NiO layer. We explain the negative SMR by the NiO "spin flop" coupled with YIG, which can be overridden at higher temperature by positive SMR contribution from YIG. This highlights the role of magnetic structure in antiferromagnets for transport of pure spin current in multilayers.
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Affiliation(s)
- Dazhi Hou
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
| | - Zhiyong Qiu
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
| | - Joseph Barker
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Koji Sato
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Kei Yamamoto
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institut für Physik, Johannes Gutenberg Universität Mainz, D-55128 Mainz, Germany
- Department of Physics, Kobe University, 1-1 Rokkodai, Kobe 657-8501, Japan
| | - Saül Vélez
- CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain
| | | | - Luis E Hueso
- CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain
| | - Fèlix Casanova
- CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain
| | - Eiji Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
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43
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Tanabe S, Ii T, Koyama S, Saitoh E, Itoh N, Ohtsuka K, Katoh Y, Shimizu A, Tomita Y. Spatiotemporal treadmill gait measurements using a laser range scanner: feasibility study of the healthy young adults. Physiol Meas 2017; 38:N81-N92. [PMID: 28327472 DOI: 10.1088/1361-6579/aa63d1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE Spatio-temporal parameters are typically used for gait analysis. Although these parameters are measured by sophisticated systems such as 3D motion capture system or optoelectronic bars, these systems cannot be deployed easily because of their high costs, large space requirements and elaborate set-up. The purpose of this study is to develope a system for measuring spatiotemporal gait parameters using a laser range scanner during treadmill gait. APPROACH To calculate accurate spatiotemporal parameters, the differences between the laser range scanner measured values and the reference values obtained from a 3D motion capture system were investigated in thirty subjects. From measurements in time and position at foot contact/off, adjustments to compensate for the differences in time and position were derived. Then, to determine the validity of the proposed system, values from the proposed system and the reference system were compared in four additional subjects. MAIN RESULTS The results indicate that the data from the laser range scanner demonstrate certain differences in time and position compared with reference values. However, when compensation values were introduced, each spatiotemporal parameter correlated well with the reference values. SIGNIFICANCE This newer system is smaller, is easier to deploy and requires less training than the 3D motion capture system.
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Affiliation(s)
- S Tanabe
- Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Toyoake, Japan
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44
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Kikkawa T, Shen K, Flebus B, Duine RA, Uchida KI, Qiu Z, Bauer GEW, Saitoh E. Magnon Polarons in the Spin Seebeck Effect. Phys Rev Lett 2016; 117:207203. [PMID: 27886475 DOI: 10.1103/physrevlett.117.207203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Indexed: 06/06/2023]
Abstract
Sharp structures in the magnetic field-dependent spin Seebeck effect (SSE) voltages of Pt/Y_{3}Fe_{5}O_{12} at low temperatures are attributed to the magnon-phonon interaction. Experimental results are well reproduced by a Boltzmann theory that includes magnetoelastic coupling. The SSE anomalies coincide with magnetic fields tuned to the threshold of magnon-polaron formation. The effect gives insight into the relative quality of the lattice and magnetization dynamics.
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Affiliation(s)
- Takashi Kikkawa
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Ka Shen
- Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
| | - Benedetta Flebus
- Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands
| | - Rembert A Duine
- Institute for Theoretical Physics and Center for Extreme Matter and Emergent Phenomena, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Ken-Ichi Uchida
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Zhiyong Qiu
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
| | - Gerrit E W Bauer
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
| | - Eiji Saitoh
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
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45
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Hou D, Qiu Z, Iguchi R, Sato K, Vehstedt EK, Uchida K, Bauer GEW, Saitoh E. Observation of temperature-gradient-induced magnetization. Nat Commun 2016; 7:12265. [PMID: 27457185 PMCID: PMC4963471 DOI: 10.1038/ncomms12265] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 06/16/2016] [Indexed: 12/03/2022] Open
Abstract
Applying magnetic fields has been the method of choice to magnetize non-magnetic materials, but they are difficult to focus. The magneto-electric effect and voltage-induced magnetization generate magnetization by applied electric fields, but only in special compounds or heterostructures. Here we demonstrate that a simple metal such as gold can be magnetized by a temperature gradient or magnetic resonance when in contact with a magnetic insulator by observing an anomalous Hall-like effect, which directly proves the breakdown of time-reversal symmetry. Such Hall measurements give experimental access to the spectral spin Hall conductance of the host metal, which is closely related to other spin caloritronics phenomena such as the spin Nernst effect and serves as a reference for theoretical calculation.
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Affiliation(s)
- Dazhi Hou
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
| | - Zhiyong Qiu
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
| | - R. Iguchi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - K. Sato
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - E. K. Vehstedt
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- London Centre for Nanotechnology and Department of Electronic and Electrical Engineering, University College London, 17-19 Gordon Street, London WC1H 0AH, UK
| | - K. Uchida
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - G. E. W. Bauer
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Kavli Institute of NanoScience, Delft University of Technology, Delft 2628 CJ, The Netherlands
| | - E. Saitoh
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai 980-8577, Japan
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
- Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan
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46
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Chen YT, Takahashi S, Nakayama H, Althammer M, Goennenwein STB, Saitoh E, Bauer GEW. Theory of spin Hall magnetoresistance (SMR) and related phenomena. J Phys Condens Matter 2016; 28:103004. [PMID: 26881498 DOI: 10.1088/0953-8984/28/10/103004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We review the so-called spin Hall magnetoresistance (SMR) in bilayers of a magnetic insulator and a metal, in which spin currents are generated in the normal metal by the spin Hall effect. The associated angular momentum transfer to the ferromagnetic layer and thereby the electrical resistance is modulated by the angle between the applied current and the magnetization direction. The SMR provides a convenient tool to non-invasively measure the magnetization direction and spin-transfer torque to an insulator. We introduce the minimal theoretical instruments to calculate the SMR, i.e. spin diffusion theory and quantum mechanical boundary conditions. This leads to a small set of parameters that can be fitted to experiments. We discuss the limitations of the theory as well as alternative mechanisms such as the ferromagnetic proximity effect and Rashba spin-orbit torques, and point out new developments.
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Affiliation(s)
- Yan-Ting Chen
- RIKEN Center for Emergent Matter Science (CEMS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands
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47
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Kirihara A, Kondo K, Ishida M, Ihara K, Iwasaki Y, Someya H, Matsuba A, Uchida KI, Saitoh E, Yamamoto N, Kohmoto S, Murakami T. Flexible heat-flow sensing sheets based on the longitudinal spin Seebeck effect using one-dimensional spin-current conducting films. Sci Rep 2016; 6:23114. [PMID: 26975208 PMCID: PMC4791552 DOI: 10.1038/srep23114] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 02/29/2016] [Indexed: 11/09/2022] Open
Abstract
Heat-flow sensing is expected to be an important technological component of smart thermal management in the future. Conventionally, the thermoelectric (TE) conversion technique, which is based on the Seebeck effect, has been used to measure a heat flow by converting the flow into electric voltage. However, for ubiquitous heat-flow visualization, thin and flexible sensors with extremely low thermal resistance are highly desired. Recently, another type of TE effect, the longitudinal spin Seebeck effect (LSSE), has aroused great interest because the LSSE potentially offers favourable features for TE applications such as simple thin-film device structures. Here we demonstrate an LSSE-based flexible TE sheet that is especially suitable for a heat-flow sensing application. This TE sheet contained a Ni0.2Zn0.3Fe2.5O4 film which was formed on a flexible plastic sheet using a spray-coating method known as "ferrite plating". The experimental results suggest that the ferrite-plated film, which has a columnar crystal structure aligned perpendicular to the film plane, functions as a unique one-dimensional spin-current conductor suitable for bendable LSSE-based sensors. This newly developed thin TE sheet may be attached to differently shaped heat sources without obstructing an innate heat flux, paving the way to versatile heat-flow measurements and management.
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Affiliation(s)
- Akihiro Kirihara
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan
| | | | - Masahiko Ishida
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan
| | - Kazuki Ihara
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan
| | - Yuma Iwasaki
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Hiroko Someya
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan.,Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan
| | - Asuka Matsuba
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Ken-ichi Uchida
- Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,PRESTO, Japan Science and Technology Agency, Saitama, 332-0012, Japan
| | - Eiji Saitoh
- Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Sendai, 980-8577, Japan.,Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,WPI, Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, 319-1195, Japan
| | | | - Shigeru Kohmoto
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
| | - Tomoo Murakami
- Smart Energy Research Laboratories, NEC Corporation, Tsukuba, 305-8501, Japan
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48
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Koyama S, Tanabe S, Saitoh E, Hirano S, Shimizu Y, Katoh M, Uno A, Takemitsu T. Characterization of unexpected postural changes during robot-assisted gait training in paraplegic patients. Spinal Cord 2015; 54:120-5. [PMID: 26261073 DOI: 10.1038/sc.2015.138] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 05/03/2015] [Accepted: 06/22/2015] [Indexed: 11/09/2022]
Abstract
STUDY DESIGN This is a retrospective study. OBJECTIVES The objectives of this study were to categorize unexpected postural changes (UPCs) during gait training in paraplegic patients with wearable gait-assist robots, to reveal the incidence of the UPC and its time-dependent changes during initial gait training period and to investigate neurological level-specific differences. SETTING This study was conducted in Fujita Health University, Aichi, Japan. METHODS We investigated five patients (46.2±14.6 years; lesion level: T6:3, T12:2). All patients had previously achieved gait with wearable robot and walker at supervision level. The UPCs were counted for 2 years and classified according to their type. The time-course data were calculated from the incidence of UPCs for 10 days from initial gait training with the walker. The neurological level-specific differences were investigated between T6 and T12 injuries. RESULTS Eighty-five UPCs were observed and classified into three categories: anterior breakdown, posterior breakdown (PBD) and mal-timing. The average rate over the entire period was 0.96±0.62 (incidents/h/subject). PBD, which was defined as hyperflexion of both hip joints, occurred with the highest frequency (0.64±0.64 incidents/h/subject). During initial gait training, there was a gradual decrease in the occurrence of UPC. For neurological level-specific differences, UPCs were observed more frequently in T6 injuries (1.36±0.35 incidents/h/subject) compared with T12 injuries (0.36±0.31 incidents/h/subject). CONCLUSION PBDs might be the result of near collisions between the trunk of the user and the walker, which make it difficult for the users to move their trunk over an anterior stance limb. Training that is focused upon well-timed forward movements of the walker might be required to avoid the occurrence of this common UPC.
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Affiliation(s)
- S Koyama
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan.,Department of Rehabilitation, Kawamura Hospital, Gifu, Japan
| | - S Tanabe
- Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Toyoake, Japan
| | - E Saitoh
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - S Hirano
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - Y Shimizu
- Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Japan
| | - M Katoh
- Department of Rehabilitation, Fujita Health University Hospital, Toyoake, Japan
| | - A Uno
- Tomei Brace Company, Seto, Japan
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49
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Inamoto Y, Saitoh E, Okada S, Kagaya H, Shibata S, Baba M, Onogi K, Hashimoto S, Katada K, Wattanapan P, Palmer JB. Anatomy of the larynx and pharynx: effects of age, gender and height revealed by multidetector computed tomography. J Oral Rehabil 2015; 42:670-7. [DOI: 10.1111/joor.12298] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2015] [Indexed: 11/30/2022]
Affiliation(s)
- Y. Inamoto
- Department of Rehabilitation Medicine; School of Medicine; Fujita Health University; Aichi Japan
- Faculty of Rehabilitation; School of Health Sciences; Fujita Health University; Aichi Japan
| | - E. Saitoh
- Department of Rehabilitation Medicine; School of Medicine; Fujita Health University; Aichi Japan
| | - S. Okada
- Faculty of Rehabilitation; School of Health Sciences; Fujita Health University; Aichi Japan
| | - H. Kagaya
- Department of Rehabilitation Medicine; School of Medicine; Fujita Health University; Aichi Japan
| | - S. Shibata
- Department of Rehabilitation Medicine; School of Medicine; Fujita Health University; Aichi Japan
| | - M. Baba
- Japanese Red Cross Ashikaga Hospital; Tochigi Japan
| | - K. Onogi
- Department of Rehabilitation Medicine; School of Medicine; Fujita Health University; Aichi Japan
| | - S. Hashimoto
- Department of Hygiene; Fujita Health University; Aichi Japan
| | - K. Katada
- Department of Radiology; Fujita Health University; Aichi Japan
| | - P. Wattanapan
- Institute of Medicine; Suranaree University of Technology; Muang Nakornratchasima, Thailand
| | - J. B. Palmer
- Department of Physical Medicine and Rehabilitation; Department of Otolaryngology-Head and Neck Surgery; and Center for Functional Anatomy and Evolution; Johns Hopkins University; Baltimore Maryland USA
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50
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Uchida K, Adachi H, Kikuchi D, Ito S, Qiu Z, Maekawa S, Saitoh E. Generation of spin currents by surface plasmon resonance. Nat Commun 2015; 6:5910. [PMID: 25569821 PMCID: PMC4354158 DOI: 10.1038/ncomms6910] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 11/20/2014] [Indexed: 11/17/2022] Open
Abstract
Surface plasmons, free-electron collective oscillations in metallic nanostructures, provide abundant routes to manipulate light–electron interactions that can localize light energy and alter electromagnetic field distributions at subwavelength scales. The research field of plasmonics thus integrates nano-photonics with electronics. In contrast, electronics is also entering a new era of spintronics, where spin currents play a central role in driving devices. However, plasmonics and spin-current physics have so far been developed independently. Here we report the generation of spin currents by surface plasmon resonance. Using Au nanoparticles embedded in Pt/BiY2Fe5O12 bilayer films, we show that, when the Au nanoparticles fulfill the surface-plasmon-resonance conditions, spin currents are generated across the Pt/BiY2Fe5O12 interface. This spin-current generation cannot be explained by conventional heating effects, requiring us to introduce nonequilibrium magnons excited by surface-plasmon-induced evanescent electromagnetic fields in BiY2Fe5O12. This plasmonic spin pumping integrates surface plasmons with spin-current physics, opening the door to plasmonic spintronics. Optical methods allow for the excitation of diverse magnetic phenomena in nanostructured materials. Here, Uchida et al. demonstrate how pure spin current may be generated across a Pt/BiY2Fe5O12 thin film interface by optically exciting surface plasmon resonance in embedded gold nanoparticles.
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Affiliation(s)
- K Uchida
- 1] Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan [2] PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan
| | - H Adachi
- 1] Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan [2] CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan
| | - D Kikuchi
- 1] Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan [2] WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Ito
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Z Qiu
- WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - S Maekawa
- 1] Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan [2] CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan
| | - E Saitoh
- 1] Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan [2] Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan [3] CREST, Japan Science and Technology Agency, Tokyo 102-0075, Japan [4] WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
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