Single-band tight-binding parameters for Fe-MgO-Fe magnetic heterostructures

TL;DR

This paper introduces a computationally efficient single-band tight-binding model for spin-polarized transport in Fe-MgO-Fe heterostructures, accurately capturing band structure effects and matching ab initio results.

Contribution

It develops a transferable single-band tight-binding model with a novel parameter extraction method based on energy-resolved transmission for magnetic heterostructures.

Findings

Successfully reproduces I-V characteristics and TMR trends.

Captures voltage and barrier width dependencies accurately.

Matches results obtained from ab initio calculations.

Abstract

We present a computationally efficient transferable single-band tight-binding model (SBTB) for spin polarized transport in heterostructures with an effort to capture the band structure effects. As an example, we apply it to study transport through Fe-MgO-Fe(100) magnetic tunnel junction devices. We propose a novel approach to extract suitable tight-binding parameters for a material by using the energy resolved transmission as the benchmark, which inherently has the bandstructure effects over the two dimensional transverse Brillouin zone. The SBTB parameters for each of the four symmetry bands for bcc Fe(100) are first proposed which are complemented with the transferable tight-binding parameters for the MgO tunnel barrier for the Delta_1 and Delta_5 bands. The non-equilibrium Green's function formalism is then used to calculate the transport. Features like I-V characteristics, voltage dependence and the barrier width dependence of the tunnel magnetoresistance ratio are captured quantitatively and the trends match well with the ones observed by ab initio methods.