Calculating the Curie Temperature reliably in diluted III-V ferromagnetic semiconductors

TL;DR

This paper introduces a semi-analytic method to accurately calculate the Curie temperature in diluted magnetic semiconductors, incorporating disorder and spin fluctuations, and validates it against experimental data.

Contribution

The authors develop a semi-analytic theory that precisely accounts for disorder and spin fluctuations in calculating Curie temperatures, using ab initio exchange couplings.

Findings

Good agreement with experimental data for Mn_xGa_{1-x}As

Predicted lower Curie temperatures for Mn_xGa_{1-x}N compared to GaAs

Dependence of Curie temperature on hole concentration

Abstract

We present a semi-analytic theory for the Curie temperature in diluted magnetic semi-conductors that treats disorder effects exactly in the effective Heisenberg Hamiltonian, and spin fluctuations within a local RPA. The exchange couplings are taken from concentration dependent {\it ab initio} estimates. The theory gives very good agreement with published data for well-annealed samples of Mn$_x$Ga$_{1-x}$As. We predict the critical temperatures for Mn$_x$Ga$_{1-x}$N lower than in doped GaAs, despite the stronger nearest-neighbour ferromagnetic coupling. We also predict the dependence on the hole concentration.