Dependence of critical current of spin transfer torque-driven magnetization dynamics on free layer thickness

TL;DR

This paper investigates how the critical current for spin transfer torque-driven magnetization switching depends on the free layer thickness, considering spin current penetration and spin pumping effects, revealing finite critical currents even at zero thickness.

Contribution

It introduces a model accounting for finite spin current penetration depth and spin pumping, showing finite critical currents at zero free layer thickness for both magnetic alignments.

Findings

Critical current remains finite as free layer thickness approaches zero.

Critical current for parallel to anti-parallel switching is larger than for reverse.

Finite spin current penetration and spin pumping influence critical current behavior.

Abstract

The dependence of the critical current of spin transfer torque-driven magnetization dynamics on the free-layer thickness was studied by taking into account both the finite penetration depth of the transverse spin current and spin pumping. We showed that the critical current remains finite in the zero-thickness limit of the free layer for both parallel and anti-parallel alignments. We also showed that the remaining value of the critical current of parallel to anti-parallel switching is larger than that of anti-parallel to parallel switching.