A theoretical study of half-metallic antiferromagnetic diluted magnetic semiconductors

Based on electronic structure calculations and statistical methods, we investigate a new class of materials for spintronic applications: half-metallic antiferromagnetic diluted magnetic semiconductors (HMAF-DMSs). As shown recently by Akai and Ogura, these DMS systems contain equal amounts of low-valent and high-valent transition metal impurities, such that their local moments exactly compensate each other. We present ab initio calculations using the KKR-CPA and the PAW-supercell methods, and show that quite a few half-metallic antiferromagnets should exist. Our calculations demonstrate that the exchange coupling parameters in these systems are dominated by a strong antiferromagnetic interaction between the two impurities. The Neel temperatures are calculated by Monte Carlo simulations and in mean-field approximation. It is shown that the latter method strongly overestimates the critical temperatures and that the more realistic values obtained by Monte Carlo techniques are rather low.