Tunnel magnetoresistance and interfacial electronic state

TL;DR

This study investigates how magnetic impurities at ferromagnetic tunnel junction interfaces affect tunnel magnetoresistance (TMR), revealing that impurity $d$-levels significantly reduce TMR by altering spin-dependent electron tunneling.

Contribution

It introduces a theoretical analysis linking interfacial electronic states modified by impurities to TMR reduction, supported by comparison with experimental and multilayer results.

Findings

TMR ratio decreases with impurity $d$-level position.

Spin-dependent $s$-electron tunneling is suppressed by impurities.

Results align with experimental data on Cr-dusted junctions.

Abstract

We study the relation between tunnel magnetoresistance (TMR) and interfacial electronic states modified by magnetic impurities introduced at the interface of the ferromagnetic tunnel junctions, by making use of the periodic Anderson model and the linear response theory. It is indicated that the TMR ratio is strongly reduced depending on the position of the $d$-levels of impurities, based on reduction in the spin-dependent $s$-electron tunneling in the majority spin state. The results are compared with experimental results for Cr-dusted ferromagnetic tunnel junctions, and also with results for metallic multilayers for which similar reduction in giant magnetoresistance has been reported.