Calculating the Curie temperature reliably in diluted III-V ferromagnetic semiconductors

We present a semi-analytic theory for the Curie temperature in diluted magnetic semiconductors that treats disorder effects exactly in the effective Heisenberg Hamiltonian, and spin fluctuations within a local RPA. The exchange couplings are taken from concentration-dependent ab initio estimates. The theory gives very good agreement with published data for well-annealed samples of MnxGa1-xAs. We predict that critical temperatures for strongly p-type MnxGa1-xN would be lower than in doped GaAs, despite the stronger nearest-neighbour ferromagnetic coupling. We also predict the dependence on the hole concentration.