Enhanced tunneling magnetoresistance in Fe$\mid$ZnSe double junctions

TL;DR

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

Contribution

The paper introduces a detailed theoretical analysis of TMR in Fe/ZnSe double junctions, demonstrating how TMR can be tuned and enhanced through the in-between Fe layer's thickness.

Findings

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

Conductance can be enhanced compared to simple junctions.

Energy spectrum explains conductance enhancement.

Abstract

We calculate the tunneling magnetoresistance (TMR) of Fe$\mid$ZnSe$\mid$Fe$\mid$ZnSe$\mid$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$\mid$ZnSe$\mid$Fe simple junctions. The electronic band structures are modeled by a parametrized tight-binding Hamiltonian fitted to {\it 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.