Tailoring the switching efficiency of magnetic tunnel junctions by the fieldlike spin-orbit torque

TL;DR

This study investigates how the fieldlike spin-orbit torque influences magnetic tunnel junction switching, demonstrating that non-collinear field and current alignment can enhance efficiency and proposing device designs to leverage this effect.

Contribution

It reveals the role of fieldlike torque in magnetic switching, showing how non-collinear alignment improves efficiency and reliability, validated by experiments and simulations.

Findings

Fieldlike torque can assist or hinder switching depending on alignment.

Non-collinear field and current alignment increases switching efficiency.

Real-time probing shows combined effects accelerate or decelerate reversal.

Abstract

Current-induced spin-orbit torques provide a versatile tool for switching magnetic devices. In perpendicular magnets, the dampinglike component of the torque is the main driver of magnetization reversal. The degree to which the fieldlike torque assists the switching is a matter of debate. Here we study the switching of magnetic tunnel junctions with a CoFeB free layer and either W or Ta underlayers, which have a ratio of fieldlike to dampinglike torque of 0.3 and 1, respectively. We show that the fieldlike torque can either assist or hinder the switching of CoFeB when the static in-plane magnetic field required to define the polarity of spin-orbit torque switching has a component transverse to the current. In particular, the non-collinear alignment of the field and current can be exploited to increase the switching efficiency and reliability compared to the standard collinear alignment. By probing individual switching events in real-time, we also show that the combination of transverse magnetic field and fieldlike torque can accelerate or decelerate the reversal onset. We validate our observations using micromagnetic simulations and extrapolate the results to materials with different torque ratios. Finally, we propose device geometries that leverage the fieldlike torque for density increase in memory applications and synaptic weight generation.