The University of Tokyo, RIKEN, Tohoku University

University of Tokyo, RIKEN, Tohoku University, University of Toyama, Osaka University, Institute of Engineering Innovation

Japan Atomic Energy Agency J-PARC Japan Science and Technology Agency (JST)

Summary of Presentations

A research group led by Hiroki Takagi, Graduate Student (at the time of the research), Rina Takagi, Assistant Professor (at the time of the research), and Shinichiro Seki, Associate Professor at the Graduate School of Engineering, The University of Tokyo, in collaboration with Taro Nakajima, Associate Professor at the Institute for Solid State Physics, and Ryotaro Arita, Professor at the Research Center for Advanced Science and Technology, has discovered that the direction of electron motion is bent due to the three-dimensional arrangement of spin. The topological Hall effect, a phenomenon in which the direction of electrons is bent due to the three-dimensional arrangement of spins, has been successfully demonstrated in an antiferromagnetic material without magnetization. The Hall effect is widely used in detecting the geomagnetic field and reading out magnetic information in ferromagnetic materials, and is usually known to occur in proportion to the magnetic field and magnetization. On the other hand, in the antiferromagnetic body focused on in this research, it has been clarified that the electrons moving in a tetrahedral spin arrangement feel a virtual magnetic field originating from the "curved space," resulting in a huge Hall effect comparable to that in ferromagnetic bodies (Figure). The above phenomenon is expected to be used as a new principle for reading out magnetic information in antiferromagnetic materials without magnetization, and is expected to lead to the development of new high-speed, high-density magnetic information devices based on antiferromagnetic materials.

The research results were published in the online edition of the British scientific journal Nature Physics on April 20, 2023 (UK summer time).

Figure: The normal Hall effect in a ferromagnet with magnetization and the topological Hall effect in an antiferromagnet without magnetization. The magnetization in the former and the virtual magnetic field induced by the three-dimensional spin arrangement in the latter cause the electron (gray circle) to bend its direction of motion, respectively. The red arrows indicate the direction of spin.

This research result was achieved with the participation of Dr. Masashi Miha, Project Assistant Professor in the Department of Physics (at the time of the research, current affiliation: Assistant Professor in the Department of Mechanical Engineering, Graduate School of Engineering, Kyoto University).

For more information, please visit the website of the Graduate School of Engineering, The University of Tokyo.