Ab-initio calculation of electronic structure of partially inverted manganese ferrite

Electronic structure of manganese ferrite is calculated using the density functional theory. Partially inverted structure with the inversion parameter y = 0.0625 is considered, using four different supercells (Mn15Fe)(A)[Fe31Mn](B)O-64 that differ in relative position of Fe-A and Mn-B. The crystal structure was optimized by minimizing the forces acting on the atoms. The spin magnetic moments m of Mn and Fe ions depend to some extent on their position in the supercell, but we found that in all cases m(Mn-B) is considerably smaller (by approx. one Bohr magneton) than m(Mn-A). This indicates strongly that the formal valence of Mn-B is 3+. Trivalent manganese in an octahedral position is expected to exhibit a Jahn-Teller effect and corresponding analysis was performed. No pronounced localization of the extra electron in the octahedral sublattice that would represent the Fe2+ ion was found. (C) 2009 Elsevier B.V. All rights reserved.