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Journal Articles

Magnetization switching process by dual spin-orbit torque in interlayer exchange-coupled systems

Masuda, Hiroto*; Yamane, Yuta*; Seki, Takeshi*; Raab, K.*; Dohi, Takaaki*; Modak, R.*; Uchida, Kenichi*; Ieda, Junichi; Kl$"a$ui, M.*; Takanashi, Koki

Applied Physics Letters, 122(16), p.162402_1 - 162402_7, 2023/04

 Times Cited Count:0

Journal Articles

Thermal stability of non-collinear antiferromagnetic Mn$$_3$$Sn 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

 Times Cited Count:0 Percentile:0(Physics, Applied)

Journal Articles

Spin and spin current; From fundamentals to recent progress

Maekawa, Sadamichi; Kikkawa, Takashi*; Chudo, Hiroyuki; Ieda, Junichi; Saito, Eiji

Journal of Applied Physics, 133(2), p.020902_1 - 020902_24, 2023/01

 Times Cited Count:1 Percentile:0(Physics, Applied)

Journal Articles

The Damage analysis for irradiation tolerant spin-driven thermoelectric device based on single-crystalline Y$$_3$$Fe$$_5$$O$$_{12}$$/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

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

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 Y$$_3$$Fe$$_5$$O$$_{12}$$/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 $$10^{10}$$ ions/cm$$^2$$ fluence and that the SSE signal is extinguished around $$10^{12}$$ ions/cm$$^2$$, 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 Y$$_3$$Fe$$_5$$O$$_{12}$$/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 Y$$_3$$Fe$$_5$$O$$_{12}$$/Pt for developing better STE devices applicable to harsh environmental usages.

Journal Articles

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

 Times Cited Count:2 Percentile:66.83(Multidisciplinary Sciences)

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.

Journal Articles

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

 Times Cited Count:2 Percentile:44.44(Physics, Applied)

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.

Journal Articles

Observation of domain structure in non-collinear antiferromagnetic Mn$$_3$$Sn thin films by magneto-optical Kerr effect

Uchimura, Tomohiro*; Yoon, J.-Y.*; Sato, Yuma*; Takeuchi, Yutaro*; Kanai, Shun*; Takechi, Ryota*; Kishi, Keisuke*; Yamane, Yuta*; DuttaGupta, S.*; Ieda, Junichi; et al.

Applied Physics Letters, 120(17), p.172405_1 - 172405_5, 2022/04

 Times Cited Count:7 Percentile:91.96(Physics, Applied)

Journal Articles

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

 Times Cited Count:1 Percentile:52.46(Physics, Multidisciplinary)

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.

Journal Articles

Observation of topological Hall torque exerted on a domain wall in the ferromagnetic oxide SrRuO$$_3$$

Yamanouchi, Michihiko*; Araki, Yasufumi; Sakai, Takaki*; Uemura, Tetsuya*; Ota, Hiromichi*; Ieda, Junichi

Science Advances (Internet), 8(15), p.eabl6192_1 - eabl6192_6, 2022/04

 Times Cited Count:2 Percentile:72.35(Multidisciplinary Sciences)

In a ferromagnetic Weyl metal SrRuO$$_3$$, a large effective magnetic field $$H_mathrm{eff}$$ exerted on a magnetic domain wall (DW) by current has been reported. We show that the ratio of $$H_mathrm{eff}$$ to current density exhibits nonmonotonic temperature dependence and surpasses those of conventional spin-transfer torques and spin-orbit torques. This enhancement is described well by topological Hall torque (THT), which is exerted on a DW by Weyl electrons emerging around Weyl points when an electric field is applied across the DW. The ratio of the $$H_mathrm{eff}$$ arising from the THT to current density is over one order of magnitude higher than that originating from spin-transfer torques and spin-orbit torques reported in metallic systems, showing that the THT may provide a better way for energy-efficient manipulation of magnetization in spintronics devices.

Journal Articles

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

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.

Journal Articles

Intrinsic torques emerging from anomalous velocity in magnetic textures

Araki, Yasufumi; Ieda, Junichi

Physical Review Letters, 127(21), p.277205_1 - 277205_7, 2021/12

 Times Cited Count:2 Percentile:40.91(Physics, Multidisciplinary)

Momentum-space topology of electrons under strong spin-orbit coupling contributes to the electrically induced torques exerting on magnetic textures insensitively to disorder or thermal fluctuation. We present a direct connection between band topology and the torques by classifying the whole torques phenomenologically. As well as the intrinsic anomalous Hall effect, the torques also emerge intrinsically from the anomalous velocity of electrons regardless of a nonequilibrium transport current. We especially point out the intrinsic contribution arising exclusively in magnetic textures, which we call the "topological Hall torque (THT)". The THT emerges in bulk crystals without any interface or surface structures. We numerically demonstrate the enhancement of the THT in comparison with the conventional spin-transfer torque in the bulk metallic ferromagnet, which accounts for the giant current-induced torque measured in ferromagnetic $$mathrm{SrRuO_3}$$.

Journal Articles

Challenge to spintronics at MLF

Shamoto, Shinichi; Ieda, Junichi

CROSS T&T, (69), p.35 - 39, 2021/10

no abstracts in English

Journal Articles

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

 Times Cited Count:53 Percentile:98.74(Chemistry, Physical)

Journal Articles

Correlation of anomalous Hall effect with structural parameters and magnetic ordering in Mn$$_{3+x}$$Sn$$_{1-x}$$ 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

 Times Cited Count:10 Percentile:79.5(Nanoscience & Nanotechnology)

Journal Articles

Intrinsic and extrinsic tunability of Rashba spin-orbit coupled emergent inductors

Ieda, Junichi; Yamane, Yuta*

Physical Review B, 103(10), p.L100402_1 - L100402_5, 2021/03


 Times Cited Count:11 Percentile:82.07(Materials Science, Multidisciplinary)

Journal Articles

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

 Times Cited Count:9 Percentile:79.5(Chemistry, Multidisciplinary)

Journal Articles

Broken C$$_{4}$$ symmetry in the tetragonal state of uniaxial strained BaCo$$_{0.9}$$Ni$$_{0.1}$$S$$_{1.9}$$

Shamoto, Shinichi; Yamauchi, Hiroki; Ikeuchi, Kazuhiko*; Kajimoto, Ryoichi; Ieda, Junichi

Physical Review Research (Internet), 3(1), p.013169_1 - 013169_9, 2021/02

Journal Articles

The Future of energy, the challenge of "spintronics"

Ieda, Junichi

FBNews, (528), p.1 - 5, 2020/12

no abstracts in English

Journal Articles

Tolerance of spin-Seebeck thermoelectricity against irradiation by swift heavy ions

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

Journal of Applied Physics, 128(8), p.083902_1 - 083902_7, 2020/08


 Times Cited Count:2 Percentile:16.57(Physics, Applied)

Journal Articles

Ultralow-energy magnon anomaly in yttrium iron garnet

Shamoto, Shinichi; Yasui, Yukio*; Matsuura, Masato*; Akatsu, Mitsuhiro*; Kobayashi, Yoshiaki*; Nemoto, Yuichi*; Ieda, Junichi

Physical Review Research (Internet), 2(3), p.033235_1 - 033235_6, 2020/08

Ultralow energy magnon in yttrium iron garnet crystal has been studied by inelastic neutron scattering in an energy range from 10 to 45 $$mu$$eV. When a magnetic field of about 0.1 T is applied along [111], ultralow energy magnon anomaly is found at 10 K.

201 (Records 1-20 displayed on this page)