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安立 裕人; 前川 禎通
Journal of Applied Physics, 117(17), p.17C710_1 - 17C710_4, 2015/05
被引用回数：6 パーセンタイル：26.86(Physics, Applied)デーモン・エッシュバッハモードと呼ばれるスピン波の局在モードが引き起こす一方向性の熱輸送現象を検出したというごく最近の実験結果について理論的に考察する。ここではフォノンとデーモン・エッシュバッハスピン波の混合系における熱輸送の現象論を発展させ、等方的なフォノンによる単純熱拡散とデーモン・エッシュバッハスピン波による熱ドリフトとの競合から方向選択的な熱輸送現象が生じることを示す。ここで発展させられた現象論は、実験で見られた非等方的な局所温度分布をよく説明することが可能である。
Gu, B.
no journal, ,
We show that the confusing sign problem of SHA in CuBi alloys between the experiment and the established theories was due to the inconsistent definitions of SHA. Once the confusion of definitions is removed there is no contradiction to a skew scattering mechanism, and thus we restore the possibility of properly microscopic understanding of the effects. We find that the SHA can be dramatically enhanced by Bi impurities close to the Cu surface. The mechanisms are two-fold. One is that the localized impurity state on surface has a decreased hybridization and combined with Coulomb correlation effect, this leads to an enhanced SHA. The other comes from the low-dimensional state of conduction electrons on surface, which results in a further enhancement of skew scattering by impurities. Our results may explain the giant SHA experimentally observed in CuBi alloys.
Xu, Z.
no journal, ,
In the present work, we found out that the local correlation effects of the impurity 5d orbitals, which did not appear in previous theoretical treatments, can give a reason in physics to explain the positive sign of the spin Hall angle of CuIr alloys seen in experiment. We have shown this by Quantum Monte Carlo (QMC) calculations based on Anderson model. The QMC methods describe the local properties of impurities, which are not always given in the usual LDA calculations. Moreover, we have confirmed our physical picture by Hartree-Fock calculations on a simplified model. We speculate that this may open up a way to control the sign of the spin Hall angle by manipulating the occupation number of the impurities.
圓谷 志郎; 楢本 洋*; 境 誠司
no journal, ,
In the graphene spintronic devices, the controls of the spin injection and ejection processes at the interfaces between graphene and ferromagnetic metal electrodes are crucial for the device operation. It has been theoretically demonstrated that graphene/Ni(111) and graphene/Co(0001) junctions could be a perfect spin filter due to the absence of the majority spin states on the Fermi surfaces of Ni(111) and Co(0001) near the K point of graphene. Meanwhile, experimental studies have reported a small magnetoresistance (MR) effect for the vertical graphene spin valves of graphene/ferromagnetic metal junctions. In this work, magnetotransport properties of graphene spin valves were investigated for the vertical graphene/ferromagnetic metal devices with a current-perpendicular-to-plane configuration. The spin polarization at the graphene/ferromagnetic interface obtained in this study is calculated to be approximately 10%, which is rather large value than previous experimental reports.
