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Meer, H.*; Schreiber, F.*; Schmitt, C.*; Ramos, R.*; 齊藤 英治; Gomonay, O.*; Sinova, J.*; Baldrati, L.*; Klui, M.*
Nano Letters, 21(1), p.114 - 119, 2021/01
被引用回数:54 パーセンタイル:97.02(Chemistry, Multidisciplinary)We unravel the origin of current-induced magnetic switching of insulating antiferromagnet/heavy metal systems. We utilize concurrent transport and magneto-optical measurements to image the switching of antiferromagnetic domains in specially engineered devices of NiO/Pt bilayers. Different electrical pulsing and device geometries reveal different final states of the switching with respect to the current direction. We can explain these through simulations of the temperature-induced strain, and we identify the thermomagnetoelastic switching mechanism combined with thermal excitations as the origin, in which the final state is defined by the strain distributions and heat is required to switch the antiferromagnetic domains. We show that such a potentially very versatile noncontact mechanism can explain the previously reported contradicting observations of the switching final state, which were attributed to spin-orbit torque mechanisms.
Baldrati, L.*; Schmitt, C.*; Gomonay, O.*; Lebrun, R.*; Ramos, R.*; 齊藤 英治; Sinova, J.*; Klui, M.*
Physical Review Letters, 125(7), p.077201_1 - 077201_6, 2020/08
被引用回数:36 パーセンタイル:91.19(Physics, Multidisciplinary)We achieve current-induced switching in collinear insulating antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is measured electrically by spin Hall magnetoresistance and confirmed by the magnetic field-induced spin-flop transition of the CoO layer. By applying current pulses and magnetic fields, we quantify the efficiency of the acting current-induced torques and estimate a current-field equivalence ratio of TAm. The Nel vector final state is in line with a thermomagnetoelastic switching mechanism for a negative magnetoelastic constant of the CoO.
Baldrati, L.*; Gomonay, O.*; Ross, A.*; Filianina, M.*; Lebrun, R.*; Ramos, R.*; Leveille, C.*; Fuhrmann, F.*; Forrest, T. R.*; Maccherozzi, F.*; et al.
Physical Review Letters, 123(17), p.177201_1 - 177201_6, 2019/10
被引用回数:118 パーセンタイル:98.30(Physics, Multidisciplinary)We probe the current-induced magnetic switching of insulating antiferromagnet-heavy-metal systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe switching of more than one-third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely, the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.
Gomonay, O.*; 山本 慧; Sinova, J.*
Journal of Physics D; Applied Physics, 51(26), p.264004_1 - 264004_9, 2018/07
被引用回数:9 パーセンタイル:41.65(Physics, Applied)反強磁性体における新奇スピン熱現象開拓のため、本稿では印可されたスピン流の存在下における熱励起されたマグノンの性質を調べる。まずスピン蓄積による熱流の生成、すなわちスピンペルチエ効果が立方晶、あるいは一軸結晶の対称性を持つ反強磁性体で生じることを予言する。この効果はマグノン緩和時間がスピン流によってマグノンのスピン分極方向に対する依存性を獲得することに由来する。このペルチエ効果は反強磁性磁壁の運動を駆動し、その駆動力は物質の温度が上昇するにつれて大きくなる。またスピン流がマグノンスピンゼーベック効果を誘起することも示す。
山本 慧; Gomonay, O.*; Sinova, J.*; Schwiete, G.*
Physical Review B, 98(1), p.014406_1 - 014406_24, 2018/07
被引用回数:1 パーセンタイル:4.92(Materials Science, Multidisciplinary)We study spin-dependent electron transport through a ferromagnetic-antiferromagnetic-normal metal tunneling junction, in the absence of spin-orbit coupling. We derive microscopic formulas for various types of spin torque acting on the antiferromagnet as well as for charge and spin currents flowing through the junction. The obtained results are applicable in the limit of slow magnetization dynamics. We identify a parameter regime in which an unconventional damping-like torque can become comparable in magnitude to the conventional Slonczewski's torque familiar from ferromagnets. Moreover, we show that the antiferromagnetic sublattice structure opens up a channel of electron transport which does not have a ferromagnetic analog and that this mechanism leads to a pronounced field-like torque. Both charge conductance and spin current transmission through the junction depend on the relative orientation of the ferromagnetic and the antiferromagnetic order parameters.
Qiu, Z.*; Hou, D.*; Barker, J.*; 山本 慧; Gomonay, O.*; 齊藤 英治*
Nature Materials, 17(7), p.577 - 580, 2018/05
被引用回数:100 パーセンタイル:95.70(Chemistry, Physical)巨大磁気抵抗とは導体絶縁体相転移の近傍で磁場により電気抵抗が大幅に変化する現象を指す。これは磁気構造と電気伝導の強い相関に由来し、数十年にわたって盛んに研究されてきた。本稿では、反強磁性絶縁体であるCrOが室温においてスピン流についての明確な導体不導体を起こすことを報告する。スピン流透過率はネール温度近傍の14度の間で2桁変化する。このスピン流についての導体不導体転移は磁場によって制御可能であり、定温で最大500%透過率が変化し事実上のスピン流透過不透過切り替えのスイッチとなる。
山本 慧; Gomonay, O.*; Sinova, J.*; Schwiete, G.*
no journal, ,
本研究では、強磁性体-反強磁性体-常磁性金属からなるトンネル接合を非平衡グリーン関数の方法を用いて調べ、種々のスピントルクおよび電荷とスピンの伝導度に対する微視的な公式を導出する。異なるタイプのトルクの間の大小関係とそのトンネル確率依存性を発表する。またこれらのトルクが磁化の運動に及ぼす影響も議論する。さらに電荷とスピンの透過率が強磁性体と反強磁性体の秩序変数の間の角に依存することを示し、その応用可能性について議論する。