Spin-polarized investigation of ferromagnetism on magnetic semiconductors Mn_xCa_1−xS in the rock-salt phase

The structural, elastic, electronic and magnetic properties of the diluted magnetic semiconductors Mn_xCa_1−xS in the rock-salt phase have been investigated using first-principles calculations with both LDA and LDA + U functional. Features such as lattice constant, bulk modulus, elastic constants, spin-polarized band structure, total and local densities of states have been computed. We predict the values of the exchange constants and the band edge spin splitting of the valence and conduction bands. The hybridization between S-3p and Mn-3d produces small local magnetic moment on the nonmagnetic Ca and S sites. The ferromagnetism is induced due to the exchange splitting of S-3p and Mn-3d hybridized bands. The total magnetic moment per Mn of Mn_xCa_1−xS is 4.4μ_B and 4.5μ_B for LDA and LDA + U functional and is independent of the Mn concentration. The unfilled Mn-3d levels reduce the local magnetic moment of Mn from its free space charge value of 5μ_B–4.4μ_B and4.5μ_B for LDA and LDA + U functional due to 3p–3d hybridization. - Highlights: • Fundamental properties of magnetic semiconductors Mn_xCa_1−xS. • Rock-salt phase of Mn_xCa_1−xS. • Magnetic properties of the diluted magnetic semiconductors Mn_xCa_1−xS. • The use of LDA + U functionals