Mössbauer Study of Cobalt-Zinc Ferrites

Abstract

Samples of the cobalt-zinc ferrite series ${\mathrm{Co}}_{1-x}{\mathrm{Zn}}_x{\mathrm{Fe}}_2{\mathrm{O}}_4$ have been studied by the Mössbauer-effect technique at 4 °K, in magnetic fields from 0 to 80 kOe, covering the full range of zinc content. The cation distributions and the hyperfine fields at ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ nuclei in $A$ and $B$ sites have been determined as a function of Zn concentration. Canted spin structures associated with ${\mathrm{Fe}}^{3+}$ ions are observed for all samples at 4 °K. At large values of $x$ the resolved spectral features provide distinct evidence of localized spin canting with a distribution of canting angles determined by the statistical distribution of nonmagnetic (${\mathrm{Zn}}^{2+}$) neighboring ions. For low concentrations of nonmagnetic ions, the distribution of hyperfine fields is, to a good approximation, independent of the distribution of canting angles, and these spectra are analyzed in terms of supertransferred hyperfine fields from neighboring ions. The temperature dependence of the hyperfine magnetic field has been determined for several samples. For samples with $x=0.4\mathrm{}$ and $x=0.6\mathrm{}$, the Néel temperatures are found to be (513 ± 5) and (322 ± 5) °K, respectively.