Magnetism in (III, Mn)-V Diluted Magnetic Semiconductors: Effective Heisenberg Model

TL;DR

This paper investigates the magnetic properties of (Ga, Mn)As and (Ga, Mn)N diluted magnetic semiconductors using an effective Heisenberg model derived from first-principles calculations, incorporating disorder effects to predict Curie temperatures.

Contribution

It introduces a numerical method based on the Tyablikov approximation to study finite-temperature magnetic properties, accounting for positional disorder in DMS.

Findings

Curie temperatures for (Ga, Mn)As match experimental data.

Predicted low Curie temperatures for (Ga, Mn)N due to percolation effects.

Noncollinear magnetic structures influence magnetic behavior at higher Mn concentrations.

Abstract

The magnetic properties of the diluted magnetic semiconductors (DMS) (Ga, Mn)As and (Ga, Mn)N are investigated by means of an effective Heisenberg model, whose exchange parameters are obtained from first-principle calculations. The finite-temperature properties of the model are studied numerically using a method based upon the Tyablikov approximation. The method properly incorporates the effects of positional disorder present in DMS. The resulting Curie temperatures for (Ga, Mn)As are in excellent agreement with experimental data. Due to percolation effects and noncollinear magnetic structures at higher Mn concentrations, our calculations predict for (Ga, Mn)N very low Curie temperatures compared to mean-field estimates.