Quantum Nano-Scale Magnetism Research Team

Principal Investigator

PI Name Yoshichika Otani
Degree D.Sci.
Title Team Leader
Brief Resume
1989 D.Sci.,Department of Physics, Keio University
1989 Research Fellow, Trinity College University of Dublin, Ireland
1991 Postdoctoral Researcher, Laboratoire Louis Néel, CNRS, France
1992 Research Instructor, Keio University
1995 Associate Professor, Tohoku University
2001 Team Leader, Quantum Nano-Scale Magnetics Team, RIKEN
2004 Professor,  ISSP University of Tokyo (-present)
2013 Team Leader, Quantum Nano-Scale Magnetism Research Team, Quantum Information Electronics Division, RIKEN Center for Emergent Matter Science (-present)

Outline

The Quantum Nano-Scale Magnetism Team fabricates ferromagnetic/nonmagnetic hybrid nanostructures from metals, semiconductors, insulators, and molecules to study quantum behaviors in domain wall displacement and magnetization dynamics mediated by spin current, a flow of spin angular momentum, and orbital current, a flow of orbital angular momentum. We focus our research on the fundamental process of interconversion and coupling between quasi-particles such as electron spin, magnon, phonon, and photon. In addition, we hope to develop a new technique for controlling spin conversion based on underlying exchange and spin-orbit interactions and a new class of low-power spintronic devices for novel energy harvesting.

Research Fields

Physics, Engineering, Materials Science

Keywords

Nanomagnetism
Spintronics
Spin current
Spin Hall effect
Edelstein effect
Magnon-phonon coupling

Results

Towards the new vision of Spintronics Devices:
Spin to charge conversion induced by mechanical oscillation

Spin conversion, the key concept of Spintronics, describes various intriguing spin-mediated interconversion phenomena at the nanoscale between electricity, light, sound, vibration, and heat. The interaction between spin and mechanical oscillation prevails not well explored among the above. Our group has demonstrated the feasibility of a novel hybrid device’s spin-mediated conversion of mechanical oscillation to electrical charge current. Surface acoustic waves (SAWs) across ferromagnetic layers induce periodic elastic deformation that drives precession magnetization dynamics such as ferromagnetic resonance (FMR), generating spin current flow into adjacent nonmagnetic layers. Interestingly, the coupling of SAWs with magnetic layers has more to offer. Our group has also demonstrated the nonreciprocal attenuation of SAWs via magneto-rotation coupling, a mechanism in which the magnetization couples to the rotational lattice motion (see figure). The achieved nonreciprocity values up to 100% opens up the route to application developments such as magneto-acoustic rectifiers. Beyond nonreciprocity, we are also exploring the enhancements of magnon-phonon coupling towards the strong coupling regime by using carefully designed acoustic cavities.  

Figure

Schematics of the magneto-rotation coupling. Depending on the propagation direction, SAWs rotate the lattice in opposite directions (as indicted by the blue and red oriented cycles in the figure). This rotational lattice motion couples with the magnetization via magnetic anisotropies, giving rise to a circularly polarized effective field, which suppresses or enhances the magnetization precession (purple cone). In this way, it induces a nonreciprocal attenuation on the SAWs.

Members

Yoshichika Otani

Team Leader yotani[at]riken.jp R

Kouta Kondou

Senior Research Scientist

Junyeon Kim

Research Scientist

Jorge Luis Puebla Nunez

Research Scientist

Thomas Patrick Lyons

Visiting Researcher

Mingxing Wu

Student Trainee

Yunyoung Hwang

Junior Research Associate

Handa Wang

Student Trainee

Liyang Liao

Student Trainee

Anjan Barman

Visiting Scientist

Tomoyuki Yokouchi

Visiting Scientist

Yasuhiro Fukuma

Visiting Scientist

Publications

  1. K. Kondou, H. Chen, T. Tomita, M. Ikhlas, T. Higo, A. H. MacDonald, S. Nakatsuji, and Y. Otani

    Giant field-like torque by the out-of-plane magnetic spin Hall effect in a topological antiferromagnet

    Nat. Commun. 12, 6491 (2021)
  2. J. Kim, D Go, H. Tsai, D. Jo, K. Kondou, H-W Lee, and Y. Otani

    Nontrivial torque generation by orbital angular momentum injection in ferromagnetic-metal/Cu/Al2O3 trilayers

    Phys. Rev. B 103, L020407 (2021)
  3. M. Xu, K. Yamamoto, J. Puebla, K. Baumgaertl, B. Rana, K. Miura, H. Takahashi, D. Grundler, S. Maekawa, and Y. Otani

    Nonreciprocal surface acoustic wave propagation via magneto-rotation coupling

    Sci. Adv. 6, eabb1724 (2020)
  4. Y. Hwang, J. Puebla, M. Xu, A. Lagarrigue, K. Kondou, and Y. Otani

    Enhancement of acoustic spin pumping by acoustic distributed Bragg reflector cavity

    Appl. Phys. Lett. 116, 252404 (2020)
  5. M. Xu, J. Puebla, F. Auvray, B. Rana, K. Kondou, and Y. Otani

    Inverse Edelstein effect induced by magnon-phonon coupling

    Phys. Rev. B 97, 180301 (2018)

Articles

お問い合わせ

#317 Main Research Building
2-1 Hirosawa, Wako, Saitama 351-0198 Japan

E-mail:
yotani[at]riken.jp

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