Spin transfer torque devices utilizing the giant spin Hall effect of tungsten

TL;DR

This paper demonstrates a giant spin Hall effect in beta-tungsten thin films, enabling efficient spin transfer torque devices with potential applications in magnetic memory and logic technologies.

Contribution

The study provides the first quantitative measurement of a large spin Hall angle in beta-tungsten, showing its effectiveness for spin torque switching in nanoscale magnetic devices.

Findings

Spin Hall angle in beta-W is approximately 0.30 to 0.33.

Efficient current-induced magnetization switching achieved.

Spin Hall effect varies with tungsten phase composition.

Abstract

We report a giant spin Hall effect (SHE) in {\beta}-W thin films. Using spin torque induced ferromagnetic resonance with a {\beta}-W/CoFeB bilayer microstrip we determine the spin Hall angle to be |\theta|=0.30\pm0.02, large enough for an in-plane current to efficiently reverse the orientation of an in-plane magnetized CoFeB free layer of a nanoscale magnetic tunnel junction adjacent to a thin {\beta}-W layer. From switching data obtained with such 3-terminal devices we independently determine |\theta|=0.33\pm0.06. We also report variation of the spin Hall switching efficiency with W layers of different resistivities and hence of variable ({\alpha} and {\beta}) phase composition.