Inelastic neutron scattering study of magnon excitation by ultrasound injection in yttrium iron garnet

Shamoto, Shinichi; Akatsu, Mitsuhiro*; Chang, L.-J.*; Nemoto, Yuichi*; Ieda, Junichi

Applied Physics Letters, 124(11), p.112402_1 - 112402_5, 2024/03

https://doi.org/10.1063/5.0189768

The magnon excitation by ultrasound injection in YFeO is studied by inelastic neutron scattering. Both longitudinal and transverse ultrasound injections enhanced the inelastic neutron scattering intensity.

Emergence of inductance and capacitance from topological electromagnetism

Araki, Yasufumi; Ieda, Junichi

Journal of the Physical Society of Japan, 92(7), p.074705_1 - 074705_9, 2023/06

https://doi.org/10.7566/JPSJ.92.074705

Topological electromagnetism owing to nontrivial momentum-space topology of electrons in insulators gives rise to diverse anomalous magnetoelectric responses. While conventional inductors and capacitors are based on classical electromagnetism described by Maxwell's equations, here we show that topological electromagnetism in combination with spin dynamics in magnets also generates an inductance or a capacitance. We build a generic framework to extract the complex impedance on the basis of topological field theory, and demonstrate the emergence of an inductance or a capacitance in several heterostructure setups. In comparison with the previously-studied emergent inductances in metallic magnets, insulators highly suppress the power loss, because of the absence of Joule heating. We show that the inductance from topological electromagnetism is achieved at low current and high frequency, and is also advantageous in its power efficiency, as characterized by the high quality factor (Q-factor).

Thermal stability of non-collinear antiferromagnetic MnSn nanodot

Sato, Yuma*; Takeuchi, Yutaro*; Yamane, Yuta*; Yoon, J.-Y.*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*

Applied Physics Letters, 122(12), p.122404_1 - 122404_5, 2023/03

https://doi.org/10.1063/5.0135709

The Damage analysis for irradiation tolerant spin-driven thermoelectric device based on single-crystalline YFeO/Pt heterostructures

Ieda, Junichi; Okayasu, Satoru; Harii, Kazuya*; Kobata, Masaaki; Yoshii, Kenji; Fukuda, Tatsuo; Ishida, Masahiko*; Saito, Eiji

IEEE Transactions on Magnetics, 58(8), p.1301106_1 - 1301106_6, 2022/08

https://doi.org/10.1109/TMAG.2022.3145888

The combination of spin-driven thermoelectric (STE) devices based on spin Seebeck effect (SSE), and radioactive isotopes as heat sources, has potential as a next-generation method of power generation in applications such as power supplies for space probes. However, there has been very limited knowledge available indicating the irradiation tolerance of spin thermoelectric devices. Through analysis using a heavy ion-beam accelerator and the hard X-ray photoemission spectroscopy (HAXPES) measurements, we show that a prototypical STE device based on YFeO/Pt heterostructures has tolerance to irradiation of high-energy heavy-ion beams. We used 320 MeV gold ion beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. By varying the dose level, we confirmed that the thermoelectric and magnetic properties of the SSE elements are not affected by the ion-irradiation dose up to ions/cm fluence and that the SSE signal is extinguished around ions/cm, in which the ion tracks almost fully cover the sample surface. In addition, the HAXPES measurements were performed to understand the effects at the interface of YFeO/Pt. The HAXPES measurements suggest that the chemical reaction that diminishes the SSE signals is enhanced with the increase of the irradiation dose. We share the current understandings of the damage analysis in YFeO/Pt for developing better STE devices applicable to harsh environmental usages.

Large antisymmetric interlayer exchange coupling enabling perpendicular magnetization switching by an in-plane magnetic field

Masuda, Hiroto*; Seki, Takeshi*; Yamane, Yuta*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Lau, Y.-C.*; Fukami, Shunsuke*; Takanashi, Koki

Physical Review Applied (Internet), 17(5), p.054036_1 - 054036_9, 2022/05

https://doi.org/10.1103/PhysRevApplied.17.054036

The antisymmetric interlayer exchange coupling (AIEC) was recently discovered, playing pivotal roles in magnetization switching of a synthetic antiferromagnet (SAF) through inducing magnetization canting. Large AIEC is reported for perpendicularly magnetized Pt/Co/Ir/Co/Pt with wedge-shaped layers. The effective field of the AIEC is related with symmetric interlayer exchange coupling, providing guides to enhance the AIEC. We develop an extended Stoner-Wohlfarth model for a SAF, revealing key factors in its magnetization switching. Combining the theoretical knowledge and the experimental results, perpendicular magnetization switching is achieved solely by an in-plane magnetic field.

Theory of Emergent Inductance with Spin-Orbit Coupling Effects

Yamane, Yuta*; Fukami, Shunsuke*; Ieda, Junichi

Physical Review Letters, 128(14), p.147201_1 - 147201_6, 2022/04

https://doi.org/10.1103/PhysRevLett.128.147201

We extend the theory of emergent inductance, which has recently been discovered in spiral magnets, to arbitrary magnetic textures by taking into account spin-orbit couplings arising in the absence of spatial inversion symmetry. We propose a new concept of spin-orbit emergent inductance, which can be formulated as originating from a dynamical Aharonov-Casher phase of an electron in ferromagnets. The spin-orbit emergent inductance universally arises in the coexistence of magnetism and the spin-orbit couplings, even with spatially uniform magnetization, allowing its stable operation in wide ranges of temperature and frequency. Revisiting the widely studied systems involving ferromagnets with spatial inversion asymmetry, with the new perspective offered by our work, will lead to opening a new paradigm in the study of spin-orbit physics and the spintronics-based power management in ultrawideband frequency range.

Magnetic Bragg peak enhancement under ultrasound injection

Shamoto, Shinichi*; Akatsu, Mitsuhiro*; Matsuura, Masato*; Kawamura, Seiko; Harii, Kazuya*; Ono, Masao*; Chang, L.-J.*; Ito, Takashi; Nemoto, Yuichi*; Ieda, Junichi

Physical Review Research (Internet), 4(1), p.013245_1 - 013245_7, 2022/03

https://doi.org/10.1103/PhysRevResearch.4.013245

Ultrasound injection effect on a magnetic Bragg peak of yttrium iron garnet has been studied by quasielastic neutron scattering. The magnetic Bragg peak is vastly enhanced with decreasing temperature. The energy width increases proportionally to the square root of the sample temperature increase induced by the ultrasound injection. Because the magnetic Bragg peak is enhanced by the lattice vibration, the enhancement is expected to relate to the spin-lattice coupling closely. An observed sharp drop above 100 K in the longitudinal mode suggests the degradation of the spin-lattice coupling. It is consistent with the decline of spin Seebeck effect with increasing temperature above 100 K, proving the degradation mechanism by the spin-lattice coupling.

Challenge to spintronics at MLF

Shamoto, Shinichi; Ieda, Junichi

CROSS T&T, (69), p.35 - 39, 2021/10

no abstracts in English

Correlation of anomalous Hall effect with structural parameters and magnetic ordering in MnSn thin films

Yoon, J.-Y.*; Takeuchi, Yutaro*; DuttaGupta, S.*; Yamane, Yuta*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*

AIP Advances (Internet), 11(6), p.065318_1 - 065318_6, 2021/06

https://doi.org/10.1063/5.0043192

Spin-orbit-induced Ising ferromagnetism at a van der Waals interface

Matsuoka, Hideki*; Barnes, S. E.*; Ieda, Junichi; Maekawa, Sadamichi; Bahramy, M. S.*; Saika, B. K.*; Takeda, Yukiharu; Wadachi, Hiroki*; Wang, Y.*; Yoshida, Satoshi*; et al.

Nano Letters, 21(4), p.1807 - 1814, 2021/02

https://doi.org/10.1021/acs.nanolett.0c04851