First-Principle Study on Half-Metallic Ferromagnetism and Structural Stability of C-Doped Alkaline-Earth Chalcogenides under Pressure

Abstract

Three half-metallic ferromagnets with NaCl structure, X4CS3(X = Mg, Ca and Sr) are investigated by the first principle calculations based on the density functional theory in thegeneralized gradient approximation. Non-spin and spin polarized calculations are done to obtain the lattice constants, the equilibrium cell volumes, the stable energies and the magnetic moments of X4CS3, and band structure and density of states for X4CS3at high pressure are calculated. From the calculations it has been found that X4CS3is stable in the FM state. The corresponding lattice constants and the equilibrium cell volumes in FM are greater than that in NM. The magnetic moment of X4CS3decrease as pressure increases, and a second order magnetic phase transition of Sr4CS3from FM to NM state at pressure of 140GPa, but a second order magnetic phase transitions of Mg4CS3and Ca4CS3have not been found. According to the band and the density of states, as the pressure increases the half-metallic nature of X4CS3destroyed.