Ab initio studies of the tunneling magneto-Seebeck effect: influence of magnetic material

TL;DR

This study uses ab initio calculations to show how the composition of magnetic materials and barrier thickness in MgO-based tunnel junctions critically influence the tunneling magneto-Seebeck effect, explaining variability in experimental results.

Contribution

It demonstrates the significant impact of alloy composition and barrier thickness on the temperature dependence of the tunneling magneto-Seebeck effect using first-principles calculations.

Findings

Small changes in alloy composition can reverse the effect's sign.

Barrier thickness alters the temperature dependence non-trivially.

Material parameters critically influence the tunneling magneto-Seebeck effect.

Abstract

We found a strong influence of the composition of the magnetic material on the temperature dependence of the tunneling magneto-Seebeck effect in $MgO$ based tunnel junctions. We use \textit{ab initio} alloy theory to consider different $Fe_xCo_{1-x}$ alloys for the ferromagnetic layer. Even a small change of the composition leads to strong changes in the magnitude or even in the sign of the tunneling magneto-Seebeck effect. This can explain differences between recent experimental results. In addition, changing the barrier thickness from six to ten monolayers of $MgO$ leads also to a non-trivial change of the temperature dependence. Our results emphasize that the tunneling magneto-Seebeck effect depends very crucially and is very sensitive to material parameters and show that further experimental and theoretical investigations are necessary.