Spin torque from tunneling through impurities in a magnetic tunnel junction

TL;DR

This paper calculates how impurities in a magnetic tunnel junction influence spin transfer torque, revealing dependence on contact polarization and magnetization angles, with implications for spintronic device control.

Contribution

It introduces a model for spin torque from impurity-assisted tunneling, highlighting the effects of contact polarization and magnetization angle dependence.

Findings

Torque is in the plane of magnetizations and proportional to sin(θ) for weak polarization.

Higher polarization introduces a significant out-of-plane torque component.

The torque's dependence on θ varies with polarization strength.

Abstract

We calculate the contribution to the spin transfer torque from sequential tunneling through impurities in a magnetic tunnel junction. For a junction with weakly polarized ferromagnetic contacts, the torque is found to be in the plane spanned by the magnetizations of the ferromagnetic contacts and proportional to $\sin \theta$, where $\theta$ is the angle between the magnetic moments. If the polarization is larger, the torque acquires a significant out-of-plane component and a different dependence on $\theta$.