Ab initio study on the role of the crystalline symmetry in the stabilization of the magnetic order in Al-doped SnS

Abstract We use first principles calculations to study the electronic and magnetic properties of undoped and Al-doped SnS and their dependence with space-group symmetry. The formation of a magnetic moment due to an impurity element was analyzed by substitutional doping in Pnma(62)-SnS and C2mb(39)-SnS symmetries. The holes introduced by cation Al-doping leads to the formation of a magnetic moment of 1.0 μ B /impurity, and a half-metallic behavior. Orbital configurations with local magnetic moments are established due to strong hybridization between { s ; p } -Al orbitals and { s ; p } -S orbitals. The collective magnetic order was analyzed by the effective exchange-coupling parameters between Al atoms at different atomic cationic sites, and different hole concentrations. These results indicate that the stabilization of the magnetic order presents a strong dependence with the spatial arrangement and the exchange pathways. For nearby dopants, and at the same holes concentration, both the Pnma and the C2mb symmetries present an AFM behavior. This collective magnetic order changes to a ferromagnetic coupling for the case in which the dopants are further away or when there is a higher holes concentration. The origin of such magnetic ordering can be understood based on the competition between hole-mediated superexchange and double exchange mechanisms. Our predictive results offer the possibility to distinguish between holes doping effect and the role of symmetry in the coordination of the dopant, of great importance to the understanding of the origin of defect-induced magnetism.