Exceptionally High, Strongly Temperature Dependent, Spin Hall Conductivity of SrRuO₃.

Abstract

Spin-orbit torques (SOT) in thin film heterostructures originate from strong spin-orbit interactions (SOI) that, in the bulk, generate a spin current due either to extrinsic spin-dependent, skew, or/and side-jump scattering or to intrinsic Berry curvature in the conduction bands. While most SOT studies have focused on materials with heavy metal components, the oxide perovskite SrRuO₃ has been predicted to have a pronounced Berry curvature. Through quantification of its spin current by the SOT exerted on an adjacent Co ferromagnetic layer, we determine that SrRuO₃ has a strongly temperature ( T)-dependent spin Hall conductivity σ _SH, increasing with the electrical conductivity, consistent with expected behavior of the intrinsic effect in the "dirty metal" regime. σ _SH is very high at low T, e.g., σ _SH > (ℏ/2 e)3 × 10⁵ Ω^-1 m^-1 at 60 K, and is largely unaffected by the SrRuO₃ ferromagnetic transition at T _c ≈ 150 K, which agrees with a recent theoretical determination that the intrinsic spin Hall effect is magnetization independent. Below T _c smaller nonstandard SOT components also develop associated with the magnetism of the oxide. Our results are consistent with the degree of RuO₆ octahedral tilt being correlated with the strength of the SOI in this complex oxide, as predicted by recent theoretical work on strontium iridate. These results establish SrRuO₃ as a very promising candidate material for implementing strong spintronics functionalities in oxide electronics.