Crossover of the intrinsic spin Hall effect in the presence of lattice expansion
Nozomi Soya, Hiroki Hayashi, Takashi Harumoto, Tenghua Gao, Satoshi Haku, Kazuya Ando
Abstract
We report the robustness of the intrinsic spin Hall effect in Pt against a change in the lattice constant. We measure spin-torque ferromagnetic resonance for $\mathrm{Pt}/{\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$ bilayers, where the lattice constant and carrier scattering time of the Pt layer are varied by incorporating the nitrogen atoms as interstitial impurities. We find that the spin Hall angle is enhanced by a factor of 3 as the resistivity of the Pt layer is increased by the nitrogen incorporation. The variation of the spin Hall conductivity is consistent with the prediction of the crossover of the intrinsic spin Hall effect from the moderately dirty regime to the dirty-metal regime. This result demonstrates the variation of the intrinsic spin Hall conductivity in Pt is dominated by the change in the scattering time, rather than the change in the band structure, under a few percent change in the lattice constant.