We analyze microscopically the valence and impurity band models of
ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with
conventional parameterization and the full potential LDA+U calculations give a
very similar picture of states near the Fermi energy which reside in an
exchange-split sp-d hybridized valence band with dominant orbital character of
the host semiconductor; this microscopic spectral character is consistent with
the physical premise of the k.p kinetic-exchange model. On the other hand, the
various models with a band structure comprising an impurity band detached from
the valence band assume mutually incompatible microscopic spectral character.
By adapting the tight-binding Anderson calculations individually to each of the
impurity band pictures in the single Mn impurity limit and then by exploring
the entire doping range we find that a detached impurity band does not persist
in any of these models in ferromagnetic (Ga,Mn)As.Comment: 29 pages, 25 figure
