Computational modeling of the defect structure, hyperfine and magnetic properties of the Mn²⁺-doped magnetite of the composition Mn_xFe_3-yO₄ (y = ⅔ x)

The defect structure, hyperfine and magnetic properties of Mn²⁺-doped Fe₃O₄ of the composition Mn_xFe_3-yO₄(y=⅔x) are modeled using atomistic and DFT calculations. The atomistic simulations show the substitution of the Mn²⁺ ions for Fe³⁺ ones at the tetrahedral sites to be energetically favorable than their substitution at the octahedral sites. These Mn²⁺ impurities are charge-balanced by the occupation of either Mn²⁺ or Fe ³⁺ ions of interstitial tetrahedral sites. The method of GGA with on-site Coulomb interaction approximation for the exchange-correlation potential is used to calculate the electronic structure, hyperfine and magnetic moments of the structurally most preferred models. The results obtained show the model in which all the Mn²⁺ ions substitute for tetrahedral Fe ³⁺ ions with Fe³⁺ ions expelled to interstitial tetrahedral sites to be consistent with the observed experimental trends of the hyperfine and magnetic properties.