Crucial role of interfacial $s$-$d$ exchange interaction in the temperature dependence of tunnel magnetoresistance

TL;DR

This paper investigates how the $s$-$d$ exchange interaction at interfaces influences the temperature-dependent decline of tunnel magnetoresistance (TMR) in spintronic devices, highlighting its critical role in TMR reduction at finite temperatures.

Contribution

It identifies the $s$-$d$ exchange interaction as a key factor in TMR temperature dependence and quantifies its impact through calculations on Fe/MgO/Fe(001).

Findings

TMR ratio decreases with increasing temperature due to $s$-$d$ exchange-induced spin-flip scattering.

The $s$-$d$ exchange interaction significantly affects TMR temperature dependence.

Material dependence of the $J_{sd}$ coupling constant is analyzed using a nonempirical method.

Abstract

The tunnel magnetoresistance (TMR) is one of the most important spintronic phenomena but its reduction at finite temperature is a severe drawback for applications. Here, we reveal a crucial determinant of the drawback, that is, the $s$-$d$ exchange interaction between conduction $s$ and localized $d$ electrons at interfacial ferromagnetic layers. By calculating the temperature dependence of the TMR ratio in Fe/MgO/Fe(001), we show that the obtained TMR ratio significantly decreases with increasing temperature owing to the spin-flip scattering in the $\Delta_1$ state induced by the $s$-$d$ exchange interaction. The material dependence of the coupling constant $J_{sd}$ is also discussed on the basis of a nonempirical method.