Coherent Tunneling and Strain Sensitivity of an All Heusler Alloy Magnetic Tunneling Junction: A First-Principles Study

TL;DR

This study uses first-principles calculations to analyze a Co2MnSb/HfIrSb magnetic tunneling junction, revealing high TMR ratios and strain-sensitive spin transport properties, advancing spintronic device potential.

Contribution

It provides a detailed first-principles analysis of the stability, electron transport, and strain effects in a Co-based Heusler alloy MTJ, highlighting its high TMR and strain-tunable properties.

Findings

High TMR ratio of 500% stable under electric fields up to 0.5 V/A

Evidence of coherent tunneling in Mn-Mn/Ir interface with spacer layers

Strain significantly affects spin transmission, with a three-fold increase under tensile strain

Abstract

Half-metallic Co-based full Heusler alloys have captured considerable attention of the researchers in the realm of spintronic applications, owing to their remarkable characteristics such as exceptionally high spin polarization at Fermi level, ultra-low Gilbert damping, and high Curie temperature. In this comprehensive study, employing density functional theory, we delve into the stability and electron transport properties of a magnetic tunneling junction (MTJ) comprising a Co$_2$MnSb/HfIrSb interface. Utilizing a standard model given by Julliere, we estimate the tunnel magnetoresistance (TMR) ratio of this heterojunction under external electric field, revealing a significantly high TMR ratio (500%) that remains almost unaltered for electric field magnitudes up to 0.5 V/A. In-depth investigation of K-dependent majority spin transmissions uncovers the occurrence of coherent tunneling for the Mn-Mn/Ir interface, particularly when a spacer layer beyond a certain thickness is employed. Additionally, we explore the impact of bi-axial strain on the MTJ by varying the in-plane lattice constants between -4% and +4%. Our spin-dependent transmission calculations demonstrate that the Mn-Mn/Ir interface manifests strain-sensitive transmission properties under both compressive and tensile strain, and yields a remarkable three-fold increase in majority spin transmission under tensile strain conditions. These compelling outcomes place the Co2MnSb/HfIrSb junction among the highly promising candidates for nanoscale spintronic devices, emphasizing the potential significance of the system in the advancement of the field.