Temperature dependence of spin-orbit torques in W/CoFeB bilayers

TL;DR

This study investigates how temperature and layer thickness affect spin-orbit torques in W/CoFeB bilayers, revealing interface effects and sign changes in effective fields with temperature variations.

Contribution

It provides new insights into temperature-dependent spin-orbit torque behavior and highlights the role of interface mixing in W/CoFeB bilayers.

Findings

Transverse effective field changes sign at 250 K for 2 nm W layer.

Interface mixing between W and CoFeB influences spin-orbit torque.

Temperature and thickness significantly affect spin-orbit torque components.

Abstract

We report on the temperature and layer thickness variation of spin-orbit torques in perpendicularly magnetized W/CoFeB bilayers. Harmonic Hall voltage measurements reveal dissimilar temperature evolutions of longitudinal and transverse effective magnetic field components. The transverse effective field changes sign at 250 K for a 2 nm thick W buffer layer, indicating a much stronger contribution from interface spin-orbit interactions compared to, for example, Ta. Transmission electron microscopy measurements reveal that considerable interface mixing between W and CoFeB is primarily responsible for this effect.