The Spin Hall effect as a probe of nonlinear spin fluctuations

非線形スピンゆらぎのプローブとしてのスピン・ホール効果

Wei, D. H.*; 新見 康洋*; Gu, B.; Ziman, T.*; 前川 禎通; 大谷 義近*

Wei, D. H.*; Niimi, Yasuhiro*; Gu, B.; Ziman, T.*; Maekawa, Sadamichi; Otani, Yoshichika*

The spin Hall effect (SHE) and its inverse have key roles in spintronic devices as they allow conversion of charge currents to and from spin currents. The conversion efficiency strongly depends on material details, such as the electronic band structure and the nature of impurities. Here we show an anomaly in the inverse SHE in weak ferromagnetic NiPd alloys near their Curie temperatures with a shape independent of material details, such as Ni concentrations. By extending Kondo's model for the anomalous Hall effect (AHE), we explain the observed anomaly as originating from the second-order nonlinear spin fluctuation of Ni moments. This brings to light an essential symmetry difference between the SHE and the AHE, which reflects the first-order nonlinear fluctuations of local moments. Our finding opens up a new application of the SHE, by which a minuscule magnetic moment can be detected.