Effects of disorder on the exchange coupling in (Ga,Mn)As diluted magnetic semiconductors

AUTOR(ES)

Silva, Antônio J. R. da, Fazzio, A., Santos, Raimundo R. dos, Oliveira, Luiz E.

FONTE

Brazilian Journal of Physics

DATA DE PUBLICAÇÃO

2006-09

RESUMO

A theoretical study of the effects of disorder on the Mn-Mn exchange interactions for Ga1-xMn xAs diluted magnetic semiconductors is presented. The disorder is intrinsically considered in the calculations, which are performed using an ab initio total energy density-functional approach, for a 128 atoms supercell, and by considering a variety of configurations with 2, 3 and 4 Mn atoms. Results are obtained for the effective J$^{Mn-Mn}_n$, from first (n = 1) all the way up to sixth (n = 6) neighbors via a Heisenberg Hamiltonian used to map the magnetic excitations from ab initio total energy calculations. One then obtains a clear dependence in the magnitudes of the J$^{Mn-Mn}_n$ with the Mn concentration x. Moreover, we show that, in the case of fixed Mn concentration, configurational disorder and/or clustering effects lead to large dispersions in the Mn-Mn exchange interactions. Also, calculations for the ground-state total energies for several configurations suggest that a proper consideration of disorder is needed when one is interested in treating temperature and annealing effects.

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