Spin Hall effect in AuCu alloys

Spin Hall effect is a phenomenon of spin current generation from an applied charge current, arising from the two distinct regimes: intrinsic and extrinsic mechanism. The intrinsic contribution derives from the Berry curvature associated with band structure of the material while extrinsic one originates from spin dependent scattering on structural defects or impurities. In previous reports, SHE has been tuned by alloying, changing the combination of the host and impurity metals or changing the concentration of the impurities in many alloy systems. Nevertheless, the mechanism of SHE is governed by either effect, the crossover between extrinsic and intrinsic regime induced by alloying has remain elusive.
In this study, we focus on AuCu as a material for observation of extrinsic-intrinsic crossover of the SHE. We demonstrate spin Hall angle (SHA) of Au_100−x Cu_x alloys by changing Cu concentration x. The SHA changes the sign only in a limited range of the Cu concentration due to the extrinsic skew scattering, while the intrinsic contribution becomes dominant with increasing the Cu concentration. These results provide an evidence of crossover from extrinsic regime to intrinsic regime in the metallic alloy system.