According to first-principles density functional calculations, the magnetic properties of Mn-doped GaN with defects, Ga1−x−yVGxMny N1−z−tVNzOt with Mn substituted at Ga sites, nitrogen vacancies VN, gallium vacancies VG and oxygen substituted at nitrogen sites were investigated. The magnetic interaction in Mn-doped GaN favoured the ferromagnetic coupling via the double exchange mechanism. The ground state was found to be well described by a model based upon a Mn3+−d5 in a high spin state coupled via a double exchange to a partially  delocalized hole accommodated in the 2p states of neighbouring nitrogen ions. The effect of defects on ferromagnetic coupling was investigated. It was found that in the presence of donor defects, such as oxygen substituted at nitrogen sites, nitrogen vacancy antiferromagnetic interactions appear, while in the case of Ga vacancies, the interactions remained ferromagnetic; in the case of acceptor defects like Mg and Zn co-doping, ferromagnetism was stabilized. The formation energies of these defects were computed. Furthermore, the half-metallic behaviour appeared in some studied compounds.

Magnetic Properties of Mn-Doped GaN with Defects: ab initio Calculations. E.Salmani, A.Benyoussef, H.Ez-Zahraouy, E.H.Saidi: Chinese Physics B, 2011, 20[8], 086601