Ferromagnetism in Cr-doped GaN: A first-principles calculation

Electronic structure, energy bands, and magnetic properties of Cr-doped GaN have been calculated from first principles using a 32 atom supercell within the frame work of linearized muffin-tin orbital tight binding method and gradient-corrected density-functional theory. The coupling between Cr atoms is found to be ferromagnetic with a magnetic moment of 2.69mu(B) at each Cr site. The magnetic moments of Ga and N sites are rather small, namely, 0.025mu(B) and -0.025mu(B), respectively, yielding a total moment of 6mu(B) per supercell. Parallel calculations done on small clusters of Cr-doped GaN also yield similar results indicating that magnetic coupling between Cr atoms results from a local phenomenon. These results are consistent with the recent experimental discovery of ferromagnetism in Cr-doped GaN single crystals.