Effects of disorder on the Curie temperature of GaMnN, GaCrN, InCrN, and InMnN diluted magnetic semiconductors

The critical Curie temperatures of ordered and disordered diluted magnetic semiconductors based on GaN, InN, CrN, and MnN compounds are investigated using the classical Heisenberg model within the mean field approximation. The equilibrium structural lattice parameters of all the structures investigated are obtained from first principles. We show that the Curie T_c temperatures of disordered GaN and InN doped with small concentrations of Mn and Cr depends, to a great extent, on the Mn and Cr concentrations. Our calculations on these systems show that a T_c above room-temperature can be observed in these systems and it is affected greatly by the degree of disorder of Mn and Cr randomly distributed on the Ga and In sites. In addition, the ferromagnetic stability in these diluted magnetic semiconductors is studied systematically. Our results indicate that 3d Mn and Cr impurity states in GaN and InN favor the ferromagnetic state rather than the spin-glass phase.