Temperature Dependent Magnetic Anisotropy in (Ga,Mn)As Layers

TL;DR

This study investigates how temperature and hole concentration influence magnetic anisotropy in (Ga,Mn)As layers, confirming theoretical predictions and revealing conditions for perpendicular or in-plane magnetic easy axes.

Contribution

It provides experimental validation of the mean-field Zener model's predictions on magnetic anisotropy dependence on temperature and hole concentration in (Ga,Mn)As.

Findings

Perpendicular easy axis observed at low temperatures with low hole concentration.

In-plane easy axis occurs near Curie temperature or after annealing.

Results support the mean-field Zener model for ferromagnetic semiconductors.

Abstract

It is demonstrated by SQUID measurements that (Ga,Mn)As films can exhibit perpendicular easy axis at low temperatures, even under compressive strain, provided that the hole concentration is sufficiently low. In such films, the easy axis assumes a standard in-plane orientation when the temperature is raised towards the Curie temperature or the hole concentration is increased by low temperature annealing. These findings are shown to corroborate quantitatively the predictions of the mean-field Zener model for ferromagnetic semiconductors. The in-plane anisotropy is also examined, and possible mechanisms accounting for its character and magnitude are discussed.