Ab initio study of Curie temperatures of diluted III-V magnetic semiconductors

TL;DR

This study uses ab initio methods to analyze how As-antisites and magnetic disorder affect the electronic structure and Curie temperatures of (Ga,Mn)As diluted magnetic semiconductors, highlighting the significant impact of impurities.

Contribution

It provides a systematic ab initio analysis of the influence of As-antisites and magnetic disorder on Curie temperatures in (Ga,Mn)As, incorporating disorder effects with the coherent potential approximation.

Findings

As-antisites reduce the Curie temperature significantly.

Impurities influence electronic structure and magnetic properties.

Calculated Curie temperatures align with experimental trends regarding Mn-content.

Abstract

The electronic structure of diluted (Ga,Mn)As magnetic semiconductors in the presence of As-antisites and magnetic disorder is studied within the framework of the local spin density approximation. Both the chemical and magnetic disorders are treated using the coherent potential approximation. A ground state with partial disorder in the local moments and with a reduced total magnetic moment appears in the presence of As-antisites. We first estimate the Curie temperature T_c from total energy differences between the ferromagnetic and the paramagnetic state by identifying these with the corresponding energy difference in a classical Heisenberg model. A more systematic approach within the framework of the mean-field approximation to estimate T_c consists in an evaluation of the effective exchange fields acting on the magnetic moment at a given site. The presence of As-antisites strongly reduces the Curie temperature. The results indicate that the effect of impurities on the electronic structure cannot be neglected and influences the Curie temperature non-negligibly. A comparison of the calculated Curie temperatures to existing experimental data indicates an increase of the donor concentration with the increase of the Mn-content.