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堀内 皓斗*; 荒木 康史; 若林 勇希*; 家田 淳一; 山ノ内 路彦*; 他7名*
Advanced Materials, p.2416091_1 - 2416091_9, 2025/00
被引用回数：0Spin Berry curvature characterizes the band topology as the spin counterpart of Berry curvature and is crucial in generating novel spintronics functionalities. By breaking the crystalline inversion symmetry, the spin Berry curvature is expected to be significantly enhanced; this enhancement will increase the intrinsic spin Hall effect in ferromagnetic materials and, thus, the spin-orbit torques (SOTs). However, this intriguing approach is not applied to devices; generally, the spin Hall effect in ferromagnet/heavy-metal bilayer is used for SOT magnetization switching. Here, SOT-induced partial magnetization switching is demonstrated in a single layer of a single-crystalline Weyl oxide SrRuO
(SRO) with a small current density of 
. Detailed analysis of the crystal structure in the seemingly perfect periodic lattice of the SRO film reveals barely discernible oxygen octahedral rotations with angles of 
near the interface with a substrate. Tight-binding calculations indicate that a large spin Hall conductivity is induced around small gaps generated at band crossings by the synergy of inherent spin-orbit coupling and band inversion due to the rotations, causing magnetization reversal. The results indicate that a minute atomic displacement in single-crystal films can induce strong intrinsic SOTs that are useful for spin-orbitronics devices.
山ノ内 路彦*; 荒木 康史; 酒井 貴樹*; 植村 哲也*; 太田 裕道*; 家田 淳一
Science Advances (Internet), 8(15), p.eabl6192_1 - eabl6192_6, 2022/04
被引用回数：9 パーセンタイル：68.16(Multidisciplinary Sciences)強磁性ワイル金属SrRuOにおける、電流によって磁壁に作用する大きな有効磁場
を報告する。電流密度に対するの比率は、非単調な温度依存性を示し、従来のスピン移行トルクおよびスピン軌道トルクの比率を上回っていることが示される。この増強効果は、磁壁に電場が印加されたときに、ワイル点の周りに出現するワイル電子によって磁壁に作用するトポロジカルホールトルク(THT)によってよく説明される。電流密度に対するTHTから生じるの比率は、金属系で報告されているスピン移行トルクおよびスピン軌道トルクから生じるものよりも1桁以上高く、THTが スピントロニクスデバイスにおける磁化の操作においてエネルギー効率の良い方法を提供する可能性があることを示している。
山ノ内 道彦*; 小山田 達郎*; 佐藤 晃一*; 太田 裕道*; 家田 淳一
IEEE Transactions on Magnetics, 55(7), p.1400604_1 - 1400604_4, 2019/07
被引用回数：4 パーセンタイル：23.18(Engineering, Electrical & Electronic)We investigated the coercive field 
for Domain Wall (DW) motion as a function of the current 
in the ferromagnetic oxide SrRuO, a model system with narrow DWs for fabricating high-density spintronics devices. The DW is moved by in the direction of the current, and is modulated linearly in . This linear relationship is consistent with an effective magnetic field 
driving the DW. The direction of DW motion and the magnitude of are well described by a model based on the field-like torque arising from the spin relaxation of conduction electrons in the DW.
Kim, J.*; Sinha, J.*; 三谷 誠司*; 林 将光*; 高橋 三郎*; 前川 禎通; 山ノ内 路彦*; 大野 英男*
Physical Review B, 89(17), p.174424_1 - 174424_8, 2014/05
被引用回数：95 パーセンタイル：93.63(Materials Science, Multidisciplinary)磁気トンネル接合素子に用いられるCoFeB/Mgoヘテロ構造膜の下地に用いられるTa膜の影響を調べた。Ta下地膜は電流による磁化反転に大きな効果を持っていることがわかった。この結果はスピン拡散モデルで解析された。
single layer with a spontaneous oxygen atomic displacement堀内 皓斗*; 若林 勇希*; 荒木 康史; 家田 淳一; 山ノ内 路彦*; 他6名*
no journal, ,
Perovskite oxide SrRuO (SRO), which is also known as a ferromagnetic Weyl semimetal, is promising for realizing efficient spin-orbitronics devices. Here, we demonstrated an SOT-induced magnetization switching in a single-phased ferromagnetic SRO single layer. An important finding is that 7.5 
10% of the magnetization in the 26 nm-thick SRO film was stably switched by the in-plane-current application. To clarify the reason for the obtained SOT in our SRO single layer, where spatial inversion symmetry seemingly is maintained, we closely analyzed the crystal structure using annular bright-field scanning transmission electron microscopy (ABF-STEM). We found that oxygen octahedral rotation (5 degrees) occurs especially near the interface between SRO and STO. By comparing the results with our theoretical calculation based on the tight-binding model, the observed partial single-layer magnetization switching can be attributed to the octahedral rotation and the associated large intrinsic spin Hall effect near the interface. We obtained a small switching current density of 3.1 5.3 MA cm
, one order of magnitude smaller than conventional SOT systems consisting of a ferromagnet/heavy metal bilayer. This result implies that only a tiny spontaneous displacement of atoms in perovskite oxides plays a pivotal role in spin-orbitronics device applications.
酒井 貴樹*; 山ノ内 路彦*; 荒木 康史; 植村 哲也*; 太田 裕道*; 家田 淳一
no journal, ,
Current-induced domain wall (DW) motion is one of schemes for electrical manipulation of magnetization direction in spintronics devices. Current density required for the DW motion in a ferromagnetic oxide SrRuO (SRO) is 1-2 orders of magnitude lower than that in ferromagnetic metals, and we have shown that the applied current acts as an effective magnetic field Heff on the DW in SRO. To elucidate the origin of the Heff, we investigated Heff in wide temperature range. The ratio of Heff acting on the DW to current increases with decreasing temperature around the ferromagnetic transition temperature, whereas it shows nonmonotonic temperature dependence at low temperatures. Since SRO has many Weyl points near Fermi level and transverse resistance shows nonmonotonic temperature dependence originating from Berry curvature arising from Weyl points, Weyl fermions can affect the DW motion.
荒木 康史; 山ノ内 路彦*; 酒井 貴樹*; 植村 哲也*; 家田 淳一
no journal, ,
We present our theoretical and experimental findings of the electric manipulation of magnetic textures enhanced by the electron topology. We first show the theory of the non-dissipative torques acting on magnetic textures, by classifying the electrically-induced spin torques phenomenologically. We propose the "topological Hall torque (THT)", which emerges from the combination of the anomalous velocity from the Berry curvature and the spin-momentum locking structure from the strong spin-orbit coupling (SOC). In contrast to the conventional spin-transfer torque (STT), which is driven by the transport current and suffers from energy dissipation by the Joule heating, the THT is capable of manipulating magnetic textures in a non-dissipative manner. The THT is present even in centrosymmetric crystals, such as the bulk WSMs. The emergence of the THT was verified experimentally, by measuring the current-induced magnetization switching in a ferromagnetic oxide SrRuO (SRO). SRO becomes ferromagnetic below the transition temperature 
147K. After preparing a domain wall (DW) in a film of SRO, we measured the effective magnetic field exerted on the DW by a current in a wide temperature range. As a result, the measured revealed a nonmonotonic temperature dependence at low temperature, and a large magnitude compared with that arising from the conventional STT and the spin-orbit torque. Those unconventional behaviors of are successfully described by the THT, in connection with the large Berry curvature of the Weyl fermions present in SRO. The idea of the THT discussed here may help design the spintronics device highly efficient, from the viewpoint of band topology.
小林 大輔*; 梯 友哉*; 廣瀬 和之*; 池田 正二*; 山ノ内 路彦*; 佐藤 英雄*; Enobio, E. C.*; 遠藤 哲郎*; 大野 英男*; 小野田 忍; et al.
no journal, ,
磁気抵抗メモリ(MRAM)の基本素子である磁気トンネル接合に重イオン放射線を照射した。試験素子は東北大学によって作製されたCoFeB/MgO/CoFeB層からなるものである。この素子は、垂直磁気異方性を持ち、スピン注入磁化反転方式によって制御される従来とは異なる特徴を有す。スピン注入磁化反転方式では、データ書き込みが素子へのパルス電流注入によって実現されるため、放射線衝突によって発生するノイズ電流による記憶データ喪失(書き換え)への懸念がある。タンデム加速器で加速した15MeV Siイオンを、中エネルギーイオン照射チェンバー、並びに、重イオンマイクロビーム形成装置と半導体デバイス微小領域照射試験装置を利用して照射したところ、用いたイオンビームにおいては記憶データの喪失が起きないことが明らかとなった。また、電圧ストレスが放射線耐性に及ぼす影響についても調査したが、実験に用いた
0.5Vの電圧ストレスの範囲では前記Siイオンビームへの耐性に変化がないことが判明した。
