Half-Metallic Property Induced by Double Exchange Interaction in the Double Perovskite BiO ( = Transitional Metal) via First-Principles Calculations.

In this paper, we identify three possible candidate series of half-metals (HM) from Bi-based double perovskites Bi'O (' = transition metal ions) through calculations utilizing the density functional theory (DFT) and full-structural optimization, in which the generalized gradient approximation (GGA) and the strong correlation effect (GGA + ) are considered. After observing the candidate materials under four types of magnetic states, i.e., ferromagnetic (FM), ferrimagnetic (FiM), antiferromagnetic (AF), and nonmagnetic (NM), we found eight promising candidates for half-metallic materials. Under the GGA scheme, there are three ferromagnetic-half-metal (FM-HM) materials, BiCrCoO, BiCrNiO and BiFeNiO, and three FiM-HM materials, BiFeZnO, BiCrZnO and BiCoZnO. With implementation of the Coulomb interaction correction (GGA + ), we find two stable half-metallic materials: BiCrNiO and BiCrZnO. We determine that the stability of some of these materials are tied to the double exchange interaction, an indirect interaction within the higher powers of localized spin interaction among transition metals via oxygen ions. Found in half-metallic materials, and especially those in the ferromagnetic (FM) state, the double exchange interaction is recognized in the FM-HM materials BiCrCoO and BiFeNiO.