A quantitative theory was presented for ferromagnetism in dilute III-V ferromagnetic semiconductors, in the presence of the 2 types of defect commonly supposed to be responsible for compensation. Those were As antisites and Mn interstitials. In each case, the description was reduced to that of an effective random Heisenberg model, with exchange integrals between active magnetic impurities provided by ab initio calculations. The effective magnetic Hamiltonian was then solved by using a semi-analytical method (locally self-consistent random-phase approximation), in which disorder was treated exactly. The measured Curie temperatures were shown to be inconsistent with the hypothesis that As antisites provided the dominant mechanism for compensation. However, if it were assumed that Mn interstitials were the main source of compensation, very good agreement was obtained between the calculated Curie temperature and the measured values; in both as-grown and annealed samples.

Compensation, Interstitial Defects and Ferromagnetism in Diluted Ferromagnetic Semiconductors. G.Bouzerar, T.Ziman, J.Kudrnovský: Physical Review B, 2005, 72[12], 125207 (5pp)