Quantum Nano-Scale Magnetism Research Team

Principal Investigator
Outline
Members
Publications
Articles

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.

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
Kouta Kondou	Senior Research Scientist
Jorge Luis Puebla Nunez	Research Scientist
You Ba	Postdoctoral Researcher
Liyang Liao	Student Trainee
Sosuke Hori	Student Trainee
Jiacheng Liu	Student Trainee

Publications

T. Yokouchi, S. Sugimoto, B. Rana, S. Seki, N. Ogawa, Y. Shiomi, S. Kasai, and Y. Otani

Pattern recognition with neuromorphic computing using magnetic field-induced dynamics of skyrmions

Sci. Adv. 8, eabq5652 (2022)
K. Kondou, M. Shiga, S. Sakamoto, H. Inuzuka, A. Nihonyanagi, F. Araoka, M. Kobayashi, S. Miwa, D. Miyajima, and Y. Otani

Chirality-Induced Magnetoresistance Due to Thermally Driven Spin Polarization

J. Am. Chem. Soc. 144, 7302-7307 (2022)
L. Y. Liao, F. H. Xue, L. Han, J. Kim, R. Q. Zhang, L. Li, J. M. Liu, X. F. Kou, C. Song, F. Pan, and Y. Otani

Efficient orbital torque in polycrystalline ferromagnetic-metal/Ru/Al₂O₃ stacks: Theory and experiment

Phys. Rev. B 105, 104434 (2022)
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)
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)

Articles

Mar 29, 2024 “Shear sound waves” provide the magic for linking ultrasound and magnetic waves

A team led by researchers from the RIKEN Center for Emergent Matter Science in Japan has succeeded in creating a strong coupling between two forms of waves—magnons and phonons—in a thin film. Imp ....
Oct 30, 2023 Simulating spins, spirals and shrinking devices

Researchers at RIKEN are trying to reverse the traditional approach to developing quantum-scale, energy-efficient electrical and computing components.
Feb 09, 2023 Brain-inspired computing system based on skyrmions ‘reads’ handwriting

Swirling magnetic whirlpools help to process data in a pattern-recognition device that mimics networks in the brain
Apr 02, 2021 New mechanism enables the electrical control of the magnetization in magnetic nanodevices

A new way to electrically generate rotation in materials made up of light elements could open the way for magnetic nanodevices
Feb 05, 2021 Inductance based on a quantum effect has the potential to miniaturize inductors

Inductors are set to join other electronic components in being miniaturized thanks to a quantum effect
Dec 25, 2020 A one-way street for sound waves

A new way for sound waves to interact with magnetic film could lead to 80% more directional control.
Sep 04, 2020 Using two acoustic reflectors triples spin-current generation

Reflecting sound waves back toward a layered component triples the amount of spin current it produces
Jul 17, 2020 Skyrmions created in a centrosymmetric material lacking geometrical frustration

Tiny magnetic swirls can form in a broader range of materials than have been used in previous experiments
Jun 12, 2020 Sound waves create skyrmions in a magnetic film

Nanoscale magnetic whirlpools can be formed in a film by applying sound waves
Sep 02, 2019 Spin-to-electric charge conversion at an interface enables detection of spiraling light

The interface between a metal and an oxide creates the right conditions for optically controlling electrons
Jul 20, 2018 Using spin current to convert mechanical vibrations into electricity

A nanodevice that generates an electrical current from a spin current, which in turn is generated by mechanical oscillations, demonstrates the versatility of electron spin to convert between ener ....
Nov 28, 2017 Spins line up for data duty

Electric fields produced by structural mismatches between two materials could be harnessed to manage data in spintronic devices
Nov 24, 2017 New-wave spintronics comes to light

Successful injection of tiny ripples into ultrathin magnetic films holds promise for computer chips that never overheat
Dec 11, 2015 Metal−oxide interfaces create a flipping point

Coating nanowires with an oxide layer can enhance by an order of magnitude the probability of ‘spin flips’ for spintronic devices