Ab initio electronic structure calculations of half-metallic ferromagnetism in calcium chalcogenides doped with B, C and N

摘要

Self-consistent ab initio calculations were carried out to study the structural, electronic and magnetic properties of nine ternary compounds Ca _4XA_3 (X=B, C and N; A=S, Se and Te). The calculations were performed by using tight-binding linear muffin tin orbital (TB-LMTO) method within the local density approximation (LDA). The calculations reveal that half-metallic ferromagnetism can be obtained for C- and N-doping with the integer magnetic moment of 2.00 _(μB) and 1.00 _(μB) per cell. However, B substitution does not induce magnetism in CaS and CaSe systems, but it produces ferromagnetism in CaTe system with magnetic moment of 2.67 _(μB) per cell. Moreover C- and N-doping enhance the stable ferromagnetic state in calcium chalcogenide systems. Spin-dependent electronic band structure, total and partial densities of state calculations demonstrate that localized magnetic moments substantially come from impurity atoms. Half-metallic ferromagnetism predominately originates from spin-polarization of electrons in 2p orbital states of C and N atoms. In addition, equilibrium lattice constant, bulk modulus, atomic local magnetic moments, half-metallic gap and robustness of half-metallicity have been calculated.