Spin torque, tunnel-current spin polarization and magnetoresistance in MgO magnetic tunnel junctions

TL;DR

This paper investigates the relationship between spin-transfer torque and tunnel magnetoresistance in MgO magnetic tunnel junctions, revealing that spin torque remains relatively stable despite significant TMR reduction under bias.

Contribution

It provides experimental evidence showing the weak dependence of spin torque on bias voltage, supporting models with magnetic-state-dependent tunnel decay lengths.

Findings

Spin torque decreases less than 10% over bias range with 40% TMR decrease

Results support magnetic-state-dependent tunnel decay length models

Implications for spintronic device stability under bias

Abstract

We examine the spin torque (ST) response of magnetic tunnel junctions (MTJs) with ultra-thin MgO tunnel barrier layers to investigate the relationship between the spin-transfer torque and the tunnel magnetoresistance (TMR) under finite bias. We find that the spin torque per unit current exerted on the free layer decreases by less than 10% over a bias range where the TMR decreases by over 40%. We examine the implications of this result for various spin-polarized tunneling models and find that it is consistent with magnetic-state-dependent effective tunnel decay lengths.