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

TL;DR

This study investigates how temperature, strain, and carrier concentrations influence magnetic anisotropy in (Ga,Mn)As layers, confirming theoretical models and revealing complex anisotropic behaviors.

Contribution

It provides experimental evidence linking magnetic anisotropy in (Ga,Mn)As to strain, temperature, and carrier concentrations, supporting the mean field Zener model predictions.

Findings

Magnetic anisotropy varies with temperature, strain, and doping levels.

In-plane uniaxial anisotropy with [110] easy axis is observed.

Cubic anisotropy dominates near T_C.

Abstract

It is demonstrated by SQUID magnetization measurements that (Ga,Mn)As films can exhibit rich characteristics of magnetic anisotropy depending not only to the epitaxial strain but being strongly influenced by the hole and Mn concentration, and temperature. This behavior reflects the spin anisotropy of the valence subbands and corroborates predictions of the mean field Zener model of the carrier mediated ferromagnetism in III-V diluted magnetic semiconductors with Mn. At the same time the existence of in-plane uniaxial anisotropy with [110] the easy axis is evidenced. This is related to the top/bottom symmetry breaking, resulting in the lowering of point symmetry of (Ga,Mn)As to the C_{2v} symmetry group. The latter mechanism coexists with the hole-induced cubic anisotropy, but takes over close to T_C.