All-Optical Vector Measurement of Spin-Orbit-Induced Torques Using Both Polar and Quadratic Magneto-Optic Kerr Effects

TL;DR

This paper introduces an all-optical method using magneto-optic Kerr effects to quantitatively measure both components of spin-orbit-induced torques in heavy-metal/ferromagnet bilayers, providing a non-invasive alternative to existing techniques.

Contribution

The study demonstrates a novel optical approach to separately quantify antidamping and effective-field spin-orbit torques using polar and quadratic Kerr effects.

Findings

Accurate measurement of spin-orbit torques in Pt/Permalloy bilayers.

Agreement of optical measurements with spin-torque ferromagnetic resonance results.

Distinct identification of torque components through polarization control.

Abstract

We demonstrate that the magneto-optic-Kerr effect with normal light incidence can be used to obtain quantitative optical measurements of both components of spin-orbit-induced torque (both the antidamping and effective-field components) in heavy-metal/ferromagnet bilayers. This is achieved by analyzing the quadratic Kerr effect as well as the polar Kerr effect. The two effects can be distinguished by properly selecting the polarization of the incident light. We use this all-optical technique to determine the spin-orbit torques generated by a series of Pt/Permalloy samples, finding values in excellent agreement with spin-torque ferromagnetic resonance measurements.