Thermal enhancement of the antiferromagnetic exchange coupling between Fe epilayers separated by a crystalline ZnSe spacer

TL;DR

This study demonstrates room-temperature antiferromagnetic coupling between Fe epilayers separated by thin ZnSe spacers, with the coupling strength increasing linearly with temperature, likely mediated by spin-dependent tunneling through defect states.

Contribution

It provides experimental evidence of thermally enhanced antiferromagnetic exchange coupling mediated by defect states in ZnSe spacers, a novel mechanism in magnetic semiconductor heterostructures.

Findings

Antiferromagnetic coupling observed below 4 nm ZnSe spacer thickness.

Coupling constant increases linearly with temperature (~5.5x10^-9 J/m2K).

Spin-dependent tunneling via defect states likely mediates the coupling.

Abstract

We have put into evidence the existence of an antiferromagnetic coupling between iron epilayers separated by a ZnSe crystalline semiconductor. The effect has been observed for ZnSe spacers thinner than 4 nm at room-temperature. The coupling constant increases linearly with temperature with a constant slope of ~5.5x 10-9 J/m2K. The mechanisms that may explain such exchange interaction are discussed in the manuscript. It results that thermally-induced effective exchange coupling mediated by spin-dependent on and off resonant tunnelling of electrons via localized mid-gap defect states in the ZnSe spacer layer appears to be the most plausible mechanism to induce the antiferromagnetic coupling.