Enhanced spin Hall effect by resonant skew scattering in the orbital-dependent Kondo effect.

The enhanced spin Hall effect in Au metal due to the resonant skew scattering is studied with first-principles band structure calculations. Especially the gigantic spin Hall angle gammaS congruent with 0.1 observed recently [T. Seki, Nature Mater. 7, 125 (2008)] is attributed to the orbital-dependent Kondo effect of Fe in the Au host metal, where the t2g orbitals are in the mixed-valence region while eg orbitals are in the Kondo limit. The enhanced spin-orbit interaction by the electron correlation in the t2g orbitals leads to the gigantic spin Hall effect. Impurities with 5d orbitals are also discussed.