2016 Fiscal Year Annual Research Report
| Project/Area Number |
25247056
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| Research Institution | Tohoku University |
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Principal Investigator |
Bauer Gerrit 東北大学, 金属材料研究所, 教授 (10620213)
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| Co-Investigator(Kenkyū-buntansha) |
野村 健太郎 東北大学, 金属材料研究所, 准教授 (00455776)
高橋 三郎 東北大学, 金属材料研究所, 准教授 (60171485)
Tretiakov Oleg 東北大学, 金属材料研究所, 助教 (50643425)
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| Project Period (FY) |
2013-04-01 – 2018-03-31
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| Keywords | spintronics / spin caloritronics / nanomechanics / nanomagnetism / spin mechanics |
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| Outline of Annual Research Achievements |
In the fourth year of the project, we continued working on the topics started in the first three years.
Previously, we formulated the fs laser excited spatiotemporal pump and probe spectroscopy that allowed direct observation of the magnon-polaron, the new quasi-particle formed by strongly coupled magnon and phonon excitations. The highlight of the past year was the extension of the study of spin transport in magnetic insulators from the ballistic regime to the diffuse regime. A Boltzmann theory of coupled magnon-phonon transport was successful to quantitatively describe the magnetic field dependence of the spin Seebeck effect as measured by T. Kikkawa in the Saitoh Group. Specifically we could associate sharp peak anomalies in the spin Seebeck voltage to magnon polaron formation that is maximized when the phonon dispersion becomes tangent to the magnon dispersion, i.e. when sound velocity and magnon group velocity agree. These experiments can gauge the acoustic relative to the magnetic quality of materials.
Other activities addressed the atomistic spin simulations of magnetic insulators, dynamics of antiferromagnets, and magnetoresistance of bilayers with topological insulators.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The field of spin mechanics is still going very strong. The discovery and explanation of the magnon polaron anomalies by our independently developed theory has attracted much attention. Spin mechanics has attracted the attention of the quantum information community.
The conference series on “Spin Mechanics” started was continued with "Spin Mechanics 4" in Canada this year. "Spin Mechanics 5" will be held in France next year and "Spin Mechanics 6" is likely to return to Japan.
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| Strategy for Future Research Activity |
The coupling of spin and mechanical angular momentum are addressed by the Landau-Lifshitz-Gilbert (LLG) equation coupled to continuum. We will continue running studies and address new topics raised by our previous results. Examples are the following:
(i)the dynamics of magnetic nanoparticles and experimental signatures of the lattice-magnetization coupling
(ii)Boltzmann-level transport equations for heat and spin currents beyond the simplest relaxation time approximation in order to better understand spin caloritronic phenomena such as the spin Seebeck effect,
(iii)Photon-magnon and phonon-magnon strong coupling phenomena
(iv)Spin-orbit interaction in rare earth substituted iron garnets.
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[Journal Article] Skyrmion Hall Effect Revealed by Direct Time-Resolved X-Ray Microscopy2017
Author(s)
K. Litzius, I. Lemesh, B. Kruger, P. Bassirian, L. Caretta, K. Richter, F. Buttner, K. Sato, Oleg A. Tretiakov, J. Forster, R. M. Reeve, M. Weigand, I. Bykova, H. Stoll, G. Schutz, G. S. D. Beach, and Mathias Klaui I. A. Ado, Oleg A. Tretiakov, and M. Titov
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Journal Title
Nature Physics
Volume: 13
Pages: 170-175
DOI
Peer Reviewed / Open Access / Int'l Joint Research / Acknowledgement Compliant
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[Journal Article] Magnon Polarons in the Spin Seebeck Effect2016
Author(s)
Takashi Kikkawa, Ka Shen, Benedetta Flebus, Rembert A. Duine, Ken-ichi Uchida, Zhiyong Qiu, Gerrit E.W. Bauer, and Eiji Saitoh
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Journal Title
Physical Review Letters
Volume: 117
Pages: 207203-1-6
DOI
Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
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[Presentation] Antiferromagnetic Skyrmions2016
Author(s)
Oleg A. Tretiakov
Organizer
KINKEN-KIST joint seminar Future electronic materials and devices beyond Si"
Place of Presentation
Tohoku University, Sendai, Japan
Year and Date
2016-10-24 – 2016-10-25
Int'l Joint Research / Invited
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[Presentation] Weyl Semimetals for Spintronics2016
Author(s)
K. Nomura
Organizer
KINKEN-KIST joint seminar, Future electronic materials and devices beyond Si
Place of Presentation
IMR, Tohoku University
Year and Date
2016-10-24
Int'l Joint Research / Invited
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[Presentation] Antiferromagnetic Skyrmions2016
Author(s)
Oleg A. Tretiakov
Organizer
International Workshop on Antiferromagnetic Spintronics
Place of Presentation
Johannes Gutenberg-Universitat, Mainz, Germany
Year and Date
2016-09-26 – 2016-09-30
Int'l Joint Research / Invited
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