57Fe,61Ni, and121Sb Mössbauer study of oxidic spinel ferrites CoxNi5/3−xFeSb1/3O4

Antimony substituted nickel ferrites Co x Ni5/3−xFeSb1/3O4 withx=0,1/3,1,4/3, and 5/3 were prepared by the common ceramic technique, and the single-phase structure was confirmed by x-ray powder diffraction.57Fe Mossbauer spectra were recorded at 4.2 K with and without an applied magnetic fieldHlong=60 kOe in order to determine the cation distribution and the spin structure. Utilizing the cation distributions and the Yafet-Kittel spin structures for B-site Fe3+ ions, derived from Mossbauer experiments the calculated magnetic moments are in excellent agreement with the experimental values at 4.2 K. The existence of Ni2+ ions in crystallographic A-sites was confirmed by61Ni Mossbauer spectroscopy. The magnitude of the supertransferred hyperfine field at121Sb nuclei is determined mainly by a covalent spin charge transfer from A-sites, occupied by Fe3+, Ni2+, and Co2+ ions, into the 5s orbital of Sb5+ ions. The different contributions of various magnetic A-site ions to H STHF Sb may be understood by combining the energy differences between the ionic configurations, connected with the electron transfer process and the related exchange integrals.