It was recalled that recent Rutherford back-scattering and particle-induced X-ray emission experiments had revealed that, in low-temperature molecular-beam epitaxially grown Ga1–xMnxAs, a significant fraction of the incorporated Mn atoms occupied tetrahedral interstitial sites in the lattice. A study was made here of the magnetic properties of these interstitial (MnI) ions. It was shown that they did not participate in hole-induced ferromagnetism. Moreover, MnI double donors could form pairs with the nearest substitutional (MnGa) acceptors. The present calculations showed that the spins in such pairs were antiferromagnetically coupled by the super-exchange. It was also shown that, for the Mn ion in another hexagonal interstitial position (which seemed to be the case in Ga1–x–yMnxBeyAs samples), the p-d interactions with holes, responsible for the ferromagnetism, were highly suppressed.

Spin Interactions of Interstitial Mn Ions in Ferromagnetic GaMnAs. J.Blinowski, P.Kacman: Physical Review B, 2003, 67[12], 121204 (4pp)