Structural and magnetic properties of MnN and ScN binaries and their ScN:Mn diluted magnetic semiconductors and Mn_xSc_1-xN alloys

Direct supercell approach calculations of the magnetic exchange interactions in Mn-doped ScN were carried out in the local spin density approximation by using the muffin-tin-orbital Green's function method. We employed the full-potential linearized-augmented plane-wave (FP-LAPW) method as used in the Wien2k code and WIEN97 package applied to a two-atoms unit cell. We found that magnetic interactions are long range interactions, affected by the randomness, band gap corrections, and carrier concentrations. In addition, we carried out calculations on the structural and magnetic properties of Mn-doped ScN diluted magnetic semiconductors and Mn_xGa_1-xN and Mn_xSc_1-xN alloys. Using total energy minimization approach we found that the global energy minimum of MnN is obtained for zinc-blende structure. If the compound is compressed by 6% the energy minimum corresponds to the rock-salt structure in disagreement with the experimentally observed slightly tetragonal distorted rock-salt structure, known as θ phase. An isostructural phase transition for Mn_xSc_1-xN alloys from zinc-blende phase to hexagonal phase was observed to occur for Mn concentration x=0.1 at a hydrostatic pressure of 18 GPa. Our results on the magnetization of GaN:Mn DMS calculated at a magnetic field B=1.5 T are also presented.