Estimation of spin-orbit torques in the presence of current-induced magnon creation and annihilation

TL;DR

This paper develops a method to accurately measure spin-orbit torques in bilayer systems by accounting for magnonic effects that influence resistance measurements, improving the reliability of torque estimates.

Contribution

It introduces a combined measurement approach to quantify magnonic contributions, refining the estimation of dampinglike and fieldlike torques in various bilayers.

Findings

Magnonic effects significantly affect torque measurements.

Neglecting magnonic contributions leads to overestimation of the dampinglike torque.

The proposed method reliably quantifies spin-orbit torques across different materials.

Abstract

We present a comprehensive set of harmonic resistance measurements of the dampinglike (DL) and fieldlike (FL) torques in Pt/CoFeB, Pt/Co, W/CoFeB, W/Co, and YIG/Pt bilayers complemented by measurements of the DL torque using the magneto-optical Kerr effect and calibrated by nitrogen vacancy magnetometry on the same devices. The magnon creation-annihilation magnetoresistances depend strongly on temperature and on the magnetic and transport properties of each bilayer, affecting the estimate of both the DL and FL torque. The DL torque, the most important parameter for applications, is overestimated by a factor of 2 in W/CoFeB and by one order of magnitude in YIG/Pt when not accounting for the magnonic contribution to the planar Hall resistance. We further show that the magnonic contribution can be quantified by combining measurements of the nonlinear longitudinal and transverse magnetoresistances, thus providing a reliable method to measure the spin-orbit torques in different material systems.