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]_BO₆₄ 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.