⁵⁷Fe,⁶¹Ni, and¹²¹Sb Mössbauer study of oxidic spinel ferrites Co_xNi_5/3−xFeSb_1/3O₄

Abstract

Antimony substituted nickel ferrites Co _x Ni_5/3−x FeSb_1/3O₄ 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 Mössbauer spectra were recorded at 4.2 K with and without an applied magnetic fieldH _long=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 Mössbauer 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 Mössbauer 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 ^Sb_STHF may be understood by combining the energy differences between the ionic configurations, connected with the electron transfer process and the related exchange integrals.