Ferromagnetism induced by calcium vacancies in Ca3BiP anti-perovskite: An ab-initio calculation

We study all possibilities of vacancy that can induce the magnetism in Ca3BiP anti-perovskite using a full-potential linearized-augmented plane-wave calculation within the generalized gradient approximation (PBE-GGA) and a modified version proposed by Becke and Johnson (TB-mBJ) for the exchange-correlation potential. The effects of spin-orbit coupling (SOC) are also considered in this study. We have examined the effect of all cation and/or anion vacancies on the magnetic structure in this system. For Ca3BiP bulk non-magnetic, the calculated band structures and densities of states show a semi-metallic and semi-conductor character obtained by PBE-GGA and TB-mBJ approximations respectively. Without spin-orbit interactions, we find that Ca3-xBiP and Ca3-xBiP1-x relaxed systems have magnetic moments of 2.44701 mu(B) and 3.96894 mu(B) respectively. Both approaches results show that the calcium and phosphorus vacancies are responsible for the magnetism in anti-perovskite Ca3BiP due to the spin-polarization that comes mainly from the valence states of the nearest atoms surrounding these vacancies. In the case of the other studied vacancies, the magnetism was not induced and all materials adopt a metallic character.