Electrical Conductivity and Hyperfine Interactions in MxFe3−xO4MxFe3−xO4, above and below TN

Abstract

For T<TNT<TN the results of the present study of the 57Fe Mössbauer spectra of Zn‐ and Ni‐substituted Fe3O4Fe3O4 are in qualitative agreement with those of recent investigations, supporting a band model for the conduction mechanism in Fe3O4Fe3O4. Asymmetric line shapes are observed, however, for the B site pattern of the substituted samples. Attempts to simulate the asymmetry using a binomial probability distribution and linear hyperfine field perturbations are only marginally successful. The effects of Cd substitution are considerably greater than those of Ni and Zn. A localized conduction mechanism appears to set in at lower x values for Cd. These results are consistent with existing ideas concerning conduction mechanisms in transition metal oxides. The band‐like character of the conduction electrons does not appear to be diminished above TN, and the isomer shifts indicate a close approach to the +3 oxidation state for all Fe ions. A quadrupole doublet and a singlet pattern with similar isomer shifts may account for the spectra above TN.