Role of phonon skew scattering in the spin Hall effect of platinum

TL;DR

This study investigates how phonon skew scattering influences the spin Hall effect in platinum by measuring the effective spin Hall angle across temperatures, revealing non-monotonic behavior consistent with theoretical models including impurity and phonon effects.

Contribution

It provides experimental evidence for the role of phonon skew scattering in the temperature dependence of the spin Hall effect in platinum.

Findings

Non-monotonic temperature dependence of spin Hall torque observed.

Effective spin Hall angle extracted from angular measurements.

Results align with theories including impurity and phonon contributions.

Abstract

We measure and analyze the effective spin Hall angle of platinum in the low residual resistivity regime by second harmonic measurements of the spin-orbit torques for a multilayer of Pt/Co/AlO$_x$. An angular dependent study of the torques allows us to extract the effective spin Hall angle responsible for the damping-like torque in the system. We observe a strikingly non-monotonic and reproducible temperature dependence of the torques. This behavior is compatible with recent theoretical predictions which include both intrinsic and extrinsic (impurities and phonons) contributions to the spin Hall effect at finite temperature.