Quantum Nano-Scale Magnetism Research Team

Principal Investigator

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

Outline

In Quantum Nano-Scale Magnetism Team, we fabricate nano-scale magnetic tunnel junctions and ferromagnetic/nonmagnetic hybrid nano-structures consisting of metals, semiconductors, and insulators to study quantum behaviors in domain wall displacement and magnetization dynamics mediated by spin current, i.e. a flow of spin angular momentum. In particular, we focus our investigation on the fundamental process of spin angular momentum conversion between quasi-particles such as electron spin, magnon and phonon to improve the efficiency to generate the spin current. We also aim at developing a new technique to control the spin conversion by using underlying exchange and spin-orbit interactions, and develop a new class of low power spintronic devices for innovative energy harvesting.

Research Fields

Physics, Engineering, Materials Sciences

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, has been investigated to gain a deeper understanding of spin dynamics and to enrich the functionalities of electronic devices. It describes various intriguing spin-mediated interconversion phenomena taking place on the nanoscale between electricity, light, sound, vibration, heat etc. However, among the above, the interaction between spin and mechanical oscillation remains largely unexplored. Since the discovery of Barnett effect, there is a continuous interest on research towards revealing the spin transfer phenomenon between mechanical angular momentum and spin. The reciprocal effect of Barnett effect was later established by Einstein and de Haas, well known as Einstein’s only experiment. In magnetic materials, mechanical oscillation can induce spin dynamics via magnon-phonon coupling. Our group has demonstrated the feasibility of spin mediated conversion of mechanical oscillation to electrical charge current in a novel hybrid device. By passing surface acoustic waves (SAWs) across ferromagnetic layers, periodic elastic deformation induced by SAWs excites precessional magnetization dynamics such as ferromagnetic resonance (FMR), generating spin current flow into adjacent nonmagnetic layers (see attached schematics). After exciting spin current through magnon-phonon coupling, with the presence of spin orbit coupling (SOC), spin current is translated into electric charge current. The success of this project advances the understanding of spin conversion phenomena and gives new insight towards future electronic devices.

Schematic illustration of surface acoustic wave induced spin current generation. The surface acoustic waves are generated by applying rf voltage on interdigital transducers, and spin current is caused by ferromagnetic resonance due to the lattice vibration. The generated spin current (js) converts to charge current (jc) via Inverse Edelstein effect at Cu/Bi2O3 interface.

Members

Yoshichika Otani

Team Leader yotani[at]riken.jp R

Kouta Kondou

Research Scientist

Bivas Rana

Research Scientist

Junyeon Kim

Postdoctoral Researcher

Jorge Luis Puebla Nunez

Postdoctoral Researcher

Tomoyuki Yokouchi

Special Postdoctoral Researcher

Florent Auvray

Student Trainee

Hanshen Tsai

Student Trainee

Mingran Xu

International Program Associate

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

Links