Mössbauer Study of Cobalt-Zinc Ferrites

TLDR

Samples of the cobalt‑zinc ferrite series Co₁₋ₓZnₓFe₂O₄ were examined by Mössbauer spectroscopy at 4 K in magnetic fields up to 80 kOe, with hyperfine fields analyzed via supertransferred contributions and their temperature dependence. Cation distributions and hyperfine fields at Fe sites vary with Zn content, revealing canted spin structures in all samples and localized canting at high Zn, while Néel temperatures for x = 0.4 and 0.6 are 513 ± 5 K and 322 ± 5 K.

Abstract

Samples of the cobalt-zinc ferrite series ${\mathrm{Co}}_{1\ensuremath{-}x}{\mathrm{Zn}}_{x}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ have been studied by the M\"ossbauer-effect technique at 4 \ifmmode^\circ\else\textdegree\fi{}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 \ifmmode^\circ\else\textdegree\fi{}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 $x=0.4$ and $x=0.6$, the N\'eel temperatures are found to be (513 \ifmmode\pm\else\textpm\fi{} 5) and (322 \ifmmode\pm\else\textpm\fi{} 5) \ifmmode^\circ\else\textdegree\fi{}K, respectively.