Strain-enhanced tunneling magnetoresistance in MgO magnetic tunnel junctions

TL;DR

This paper demonstrates that applying controllable mechanical strain to MgO magnetic tunnel junctions can significantly enhance their tunneling magnetoresistance, offering a new method to tune quantum transport properties at the nanoscale.

Contribution

The study shows that strain can be used to enhance TMR in MgO MTJs and correlates this effect with coherent spin tunneling, supported by quantum transport calculations.

Findings

Strain increases TMR ratio by approximately twofold.

Enhanced TMR is linked to coherent spin tunneling.

Quantum transport calculations support experimental results.

Abstract

While the effects of lattice mismatch-induced strain, mechanical strain, as well as the intrinsic strain of thin films are sometimes detrimental, resulting in mechanical deformation and failure, strain can also be usefully harnessed for applications such as data storage, transistors, solar cells, and strain gauges, among other things. Here, we demonstrate that quantum transport across magnetic tunnel junctions (MTJs) can be significantly affected by the introduction of controllable mechanical strain, achieving an enhancement factor of ~2 in the experimental tunneling magnetoresistance (TMR) ratio. We further correlate this strain-enhanced TMR with coherent spin tunneling through the MgO barrier. Moreover, the strain-enhanced TMR is analyzed using non-equilibrium Green's function (NEGF) quantum transport calculations. Our results help elucidate the TMR mechanism at the atomic level and can provide a new way to enhance, as well as tune, the quantum properties in nanoscale materials and devices.