Spin wave amplification using the spin Hall effect in permalloy/platinum bilayers

TL;DR

This paper demonstrates that the spin Hall effect in permalloy/platinum bilayers can effectively amplify or attenuate propagating spin waves, with a significant change in relaxation rate driven by electrical current.

Contribution

It provides experimental evidence of spin Hall effect-induced spin wave amplification in permalloy/Pt bilayers, with a high effective spin Hall angle of 0.13.

Findings

Spin-wave relaxation rate changes linearly with current density.

Up to 14% change in relaxation rate at 2.3×10^{11} A/m^2.

Spin Hall effect as an efficient method for spin wave control.

Abstract

We investigate the effect of an electrical current on the attenuation length of a 900 nm wavelength spin-wave in a permalloy/Pt bilayer using propagating spin-wave spectroscopy. The modification of the spin-wave relaxation rate is linear in current density, reaching up to 14% for a current density of 2.3$\times10^{11} $A/m$^2$ in Pt. This change is attributed to the spin transfer torque induced by the spin Hall effect and corresponds to an effective spin Hall angle of 0.13, which is among the highest values reported so far. The spin Hall effect thus appears as an efficient way of amplifying/attenuating propagating spin waves.