Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers

TL;DR

This study investigates the inverse spin Hall effect induced by spin pumping in permalloy/normal metal bilayers, providing precise measurements of spin Hall angles across different metals and validating a theoretical model that accounts for magnetization dynamics.

Contribution

The paper presents a comprehensive experimental and theoretical analysis of spin pumping and inverse spin Hall effect in bilayers, with high-precision determination of spin Hall angles for multiple metals.

Findings

Good agreement between experiment and theory including AMR and ISHE contributions

Spin Hall angles measured with high precision for Pt, Pd, Au, and Mo

Analysis accounts for magnetization trajectory effects

Abstract

Spin pumping is a mechanism that generates spin currents from ferromagnetic resonance (FMR) over macroscopic interfacial areas, thereby enabling sensitive detection of the inverse spin Hall effect that transforms spin into charge currents in non-magnetic conductors. Here we study the spin-pumping-induced voltages due to the inverse spin Hall effect in permalloy/normal metal bilayers integrated into coplanar waveguides for different normal metals and as a function of angle of the applied magnetic field direction, as well as microwave frequency and power. We find good agreement between experimental data and a theoretical model that includes contributions from anisotropic magnetoresistance (AMR) and inverse spin Hall effect (ISHE). The analysis provides consistent results over a wide range of experimental conditions as long as the precise magnetization trajectory is taken into account. The spin Hall angles for Pt, Pd, Au and Mo were determined with high precision to be $0.013\pm0.002$, $0.0064\pm0.001$, $0.0035\pm0.0003$ and $-0.0005\pm0.0001$, respectively.