The dominancy of damping like torque for the current induced magnetization switching in Pt/Co/W multilayers

TL;DR

This study investigates spin-orbit torques in Pt/Co/W multilayers, revealing that damping-like torque dominates over field-like torque, contrasting with other structures like Pt/Co/AlOx.

Contribution

It demonstrates the dominance of damping-like torque in Pt/Co/W films, providing new insights into spin-orbit torque mechanisms in multilayer structures.

Findings

Damping-like torque is dominant in Pt/Co/W films.

Both damping-like and field-like torques are strong in Pt/Co/AlOx.

The structure influences the relative strength of SOT components.

Abstract

Two classes of spin-orbit coupling (SOC) mechanisms have been considered as candidate sources for the spin orbit torque (SOT): the spin Hall Effect (SHE) in heavy metals with strong SOC and the Rashba effect arising from broken inversion symmetry at material surfaces and interfaces. In this work, we have investigated the SOT in perpendicularly magnetized Pt/Co/W films, which is compared with the results in Pt/Co/AlOx films. Theoretically, in the case of the asymmetric structure of trilayers with opposite sign of spin Hall angle, both damping like torque and field like torque due to the SHE and the Rashba effect will be enhanced. Using the harmonic measurements, we have characterized the effective fields corresponding to the damping like torque and the field like torque, but we have found the dominancy of damping like torque in the Pt/Co/W films. It is much different from the results in the Pt/Co/AlOx films, in which both the damping like torque and the field like torque are strong.