Ordering effects in diluted magnetic semiconductors

TL;DR

This paper reviews a two-step approach combining first-principles calculations and statistical physics to analyze the electronic and magnetic properties of diluted magnetic semiconductors, with a focus on Ga_{1-x}Mn_{x}As.

Contribution

It introduces a comprehensive method for modeling diluted magnetic semiconductors, integrating electronic structure calculations with statistical physics analysis, and applies it to Ga_{1-x}Mn_{x}As.

Findings

Identification of clustering tendencies in Ga_{1-x}Mn_{x}As

Estimation of formation energies for compensating defects

Demonstration of the strong dependence of Curie temperature on sample preparation

Abstract

We review recently developed two-step approach for description of electronic and magnetic properties of a new class of materials, the diluted magnetic semiconductors. In the first step we construct, on the basis of the state-of-the-art first-principles electronic structure calculations, the effective Ising and Heisenberg Hamiltonians which describe, respectively, the alloy phase stability and the magnetic excitations in the system. In the second step, we analyze properties of these effective Hamiltonians by various methods of statistical physics. As a case study, the prototypical diluted magnetic semiconductor Ga_{1-x}Mn_{x}As is studied in detail. We determine, among others, a possibility for clustering in this system, formation energies of various compensating defects, and estimate short-range order parameters describing ordering tendencies in a system. On the other hand, by using recently developed local random-phase approximation approach, we evaluate the system Curie temperature and demonstrate its strong dependence on the sample preparation. We also emphasize the relevance of proper inclusion of the randomness in positions of magnetic impurities for a reliable estimate of the system critical temperature. Finally, we compare calculated Curie temperatures with available experimental data and briefly mention relation to other theoretical approaches.