Annealing-dependence of Exchange Bias in MnO/Ga1-xMnxAs Heterostructures

TL;DR

This study investigates how annealing affects exchange bias in MnO/Ga1-xMnxAs heterostructures, revealing that annealing in air converts Mn to MnO, which is essential for exchange bias.

Contribution

It demonstrates that annealing induces Mn oxidation to MnO, enabling exchange bias in MnO/Ga1-xMnxAs heterostructures, a novel insight into interface engineering.

Findings

Exchange bias appears only after air annealing.

Mn overlayer must be converted to MnO for exchange bias.

X-ray photoelectron spectroscopy confirms MnO formation.

Abstract

We discuss the annealing-dependence of exchange bias in Ga1-xMnxAs epilayers that are overgrown with Mn. Although pure Mn is a known antiferromagnet, we find that the as-grown Mn overlayer does not produce any exchange coupling with Ga1-xMnxAs. Rather, our studies indicate that annealing in air is essential for creating the standard signatures of an exchange bias (a clear shift in the magnetization hysteresis loop and an increased coercive field). We use x-ray photoelectron spectroscopy to characterize the compositional depth profile of both as-grown and rapid thermal annealed samples. These studies demonstrate that the cleanest exchange bias arises when the Mn overlayer is completely converted into MnO.