Enhanced tunneling magnetoresistance in Fe|ZnSe double junctions

TL;DR

This study models and analyzes the tunneling magnetoresistance in Fe|ZnSe|Fe|ZnSe|Fe double junctions, showing that TMR can be significantly enhanced by adjusting the thickness of the intermediate Fe layer, with implications for spintronics.

Contribution

It provides a theoretical analysis of TMR in double magnetic tunnel junctions, demonstrating tunability and enhancement through in-between layer thickness variations.

Findings

TMR depends strongly on the in-between Fe layer's thickness.

Conductance for each spin channel can be enhanced compared to simple junctions.

The conductance enhancement is explained by the junctions' energy spectrum.

Abstract

We calculate the tunneling magnetoresistance (TMR) of Fe|ZnSe|Fe|ZnSe|Fe (001) double magnetic tunnel junctions as a function of the in-between Fe layer's thickness, and compare these results with those of Fe|ZnSe|Fe simple junctions. The electronic band structures are modeled by a parametrized tight-binding Hamiltonian fitted to ab initio calculations, and the conductance is calculated within the Landauer formalism expressed in terms of Green's functions. We find that the conductances for each spin channel and the TMR strongly depend on the in-between Fe layer's thickness, and that in some cases they are enhanced with respect to simple junctions, in qualitative agreement with recent experimental studies performed on similar systems. By using a 2D double junction as a simplified system, we show that the conductance enhancement can be explained in terms of the junctions energy spectrum. These results are relevant for spintronics because they demonstrate that the TMR in double junctions can be tuned and enhanced by varying the in-between metallic layer's thickness.