A Comparative Study on Spin-Orbit Torque Efficiencies from W/ferromagnetic and W/ferrimagnetic Heterostructures

TL;DR

This study compares spin-orbit torque efficiencies in W/ferromagnetic and W/ferrimagnetic heterostructures, revealing microstructure-dependent variations and highlighting the potential of resistive W phases for magnetic control.

Contribution

It provides a systematic analysis of how W layer microstructure influences spin-orbit torque efficiency in different magnetic heterostructures, demonstrating the role of resistive phases.

Findings

Maximum DL-SOT efficiencies of ~0.144 and ~0.116 achieved with partially amorphous W layers.

Spin Hall effect from resistive W phases can effectively control magnetic layers.

Microstructure of W buffer layer significantly impacts spin transport properties.

Abstract

It has been shown that W in its resistive form possesses the largest spin-Hall ratio among all heavy transition metals, which makes it a good candidate for generating efficient dampinglike spin-orbit torque (DL-SOT) acting upon adjacent ferromagnetic or ferrimagnetic (FM) layer. Here we provide a systematic study on the spin transport properties of W/FM magnetic heterostructures with the FM layer being ferromagnetic Co$_{20}$Fe$_{60}$B$_{20}$ or ferrimagnetic Co$_{63}$Tb$_{37}$ with perpendicular magnetic anisotropy. The DL-SOT efficiency $|\xi_{DL}|$, which is characterized by a current-induced hysteresis loop shift method, is found to be correlated to the microstructure of W buffer layer in both W/Co$_{20}$Fe$_{60}$B$_{20}$ and W/Co$_{63}$Tb$_{37}$ systems. Maximum values of $|\xi_{DL}|\approx 0.144$ and $|\xi_{DL}|\approx 0.116$ are achieved when the W layer is partially amorphous in the W/Co$_{20}$Fe$_{60}$B$_{20}$ and W/Co$_{63}$Tb$_{37}$ heterostructures, respectively. Our results suggest that the spin Hall effect from resistive phase of W can be utilized to effectively control both ferromagnetic and ferrimagnetic layers through a DL-SOT mechanism.