Electrical coherent driving of chiral antiferromagnet

Takeuchi, Yutaro*; Sato, Yuma*; Yamane, Yuta*; Yoon, J.-Y.*; Kanno, Yukinori*; Uchimura, Tomohiro*; De Zoysa, K. V.*; Han, J.*; Kanai, Shun*; Ieda, Junichi; et al.

Science, 389(6762), p.830 - 834, 2025/08

https://doi.org/10.1126/science.ado1611

Room-temperature flexible manipulation of the quantum-metric structure in a topological chiral antiferromagnet

Han, J.*; Uchimura, Tomohiro*; Araki, Yasufumi; Yoon, J.-Y.*; Takeuchi, Yutaro*; Yamane, Yuta*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*

Nature Physics, 20(7), p.1110 - 1117, 2024/07

https://doi.org/10.1038/s41567-024-02476-2

Quantum metric and Berry curvature are two fundamental and distinct factors to describe the geometry of quantum eigenstates. While Berry curvature is known for playing crucial roles in several condensed-matter states, quantum metric, which was predicted to induce new classes of topological phenomena, has rarely been touched, particularly in an ambient circumstance. Using a topological chiral antiferromagnet MnSn adjacent to Pt, at room temperature, we successfully manipulate the quantum-metric structure of electronic states through its interplay with the nanoscale spin texture at the MnSn/Pt interface. This is manifested by a time-reversal-odd second-order Hall effect that is robust against extrinsic electron scattering, in contrast to any transport effects from the Berry curvature. We also verify the flexibility of controlling the quantum-metric structure, as the interacting spin texture can be tuned by moderate magnetic fields or by interface engineering via spin-orbit interactions. Our work paves a way for harnessing the quantum-metric structure to unveil emerging topological physics in practical environments and to build applicable nonlinear devices.

Local bifurcation with spin-transfer torque in superparamagnetic tunnel junctions

Funatsu, Takuya*; Kanai, Shun*; Ieda, Junichi; Fukami, Shunsuke*; Ohno, Hideo*

Nature Communications (Internet), 13, p.4079_1 - 4079_8, 2022/07

AA2021-0782.pdf:1.86MB

https://doi.org/10.1038/s41467-022-31788-1

Modulation of the energy landscape by external perturbations governs various thermally-activated phenomena, described by the Arrhenius law. Thermal fluctuation of nanoscale magnetic tunnel junctions with spin-transfer torque (STT) shows promise for unconventional computing, whereas its rigorous representation, based on the Neel-Arrhenius law, has been controversial. In particular, the exponents for thermally-activated switching rate therein, have been inaccessible with conventional thermally-stable nanomagnets with decade-long retention time. Here we approach the Neel-Arrhenius law with STT utilising superparamagnetic tunnel junctions that have high sensitivity to external perturbations and determine the exponents through several independent measurements including homodyne-detected ferromagnetic resonance, nanosecond STT switching, and random telegraph noise. Furthermore, we show that the results are comprehensively described by a concept of local bifurcation observed in various physical systems. The findings demonstrate the capability of superparamagnetic tunnel junction as a useful tester for statistical physics as well as sophisticated engineering of probabilistic computing hardware with a rigorous mathematical foundation.

Chiral-spin rotation of non-collinear antiferromagnet by spin-orbit torque

Takeuchi, Yutaro*; Yamane, Yuta*; Yoon, J.-Y.*; Ito, Ryuichi*; Jinnai, Butsurin*; Kanai, Shun*; Ieda, Junichi; Fukami, Shunsuke*; Ohno, Hideo*

Nature Materials, 20(10), p.1364 - 1370, 2021/10

https://doi.org/10.1038/s41563-021-01005-3

Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy

Okada, Atsushi*; He, S.*; Gu, B.; Kanai, Shun*; Soumyanarayanan, A.*; Lim, S. T.*; Tran, M.*; Mori, Michiyasu; Maekawa, Sadamichi; Matsukura, Fumihiro*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 144(15), p.3815 - 3820, 2017/04

http://doi.org/10.1073/pnas.1613864114

Electron spectrra from singlet and triplet states of Ne produced by low energy Ne+He, Ne and Ar collisions

Kitazawa, Shinichi; Ida, H.*; Matsui, Y.*; Takayanagi, Toshinobu*; Wakiya, K.*; Iemura, K.*; Otani, Shunsuke*; Suzuki, H.*; Kanai, Yasuyuki*; Safronova, U. I.*

Journal of Physics B; Atomic, Molecular and Optical Physics, 34(16), p.3205 - 3220, 2001/08

https://doi.org/10.1088/0953-4075/34/16/301

no abstracts in English

L X-ray spectra of Fe and Cu by 0.75 MeV/u H, He, Si and Ar ion impacts

Kageyama, H.*; Kawatsura, Kiyoshi*; Takahashi, R.*; Arai, Shigeyoshi*; Kambara, Tadashi*; Oura, Masaki*; Papp, T.*; Kanai, Yasuyuki*; Awaya, Yoko*; Takeshita, Hidefumi; et al.

Nuclear Instruments and Methods in Physics Research B, 107(1-4), p.47 - 50, 1996/00

https://doi.org/10.1016/0168-583X(95)00838-1

no abstracts in English

Assessment of dust dispersion data for future safety analysis of Fukushima Daiichi fuel debris retrieval, 24; Small-scale fabrication and characterization of as-melted fuel debris pieces containing uranium

Takano, Masahide; Sudo, Ayako; Nakamura, Kinya*; Koyama, Tadafumi*; Uozumi, Koichi*; Kanai, Taizo*; Kanagawa, Shun*; Iwata, Yuichi*; Totsuka, Fumio*; Mogi, Kazutaka*; et al.

no journal, , 

Simulated fuel debris in RPV and CV containing uranium were fabricated by light-concentrating heating technique, respectively, to provide them for cutting tests with disc cutter. Characteristic data such as bulk density, microstructure, formed phases and micro-hardness on cross-section were obtained.