Relaxation times in nickel-zinc ferrite by the Mössbauer effect

Mössbauer studies of Ni1–xZnxFe2O4 for x = 0.5 and 0.75 were carried out at various temperatures for the samples on which neutron diffraction investigations have already been reported [1]. The Mössbauer studies reveal that the reduction of nuclear hyperfine splitting with increase of temperature is much more than that predicted by corresponding decrease in sub-lattice magnetization. It is also observed that at temperatures well below the reported Néel temperatures, well resolved nuclear Zeeman splitting is not observed and the observed spectral shapes are characteristic of relaxed spectra in a large range of temperature. This is explained by the assumption of collective spin flipping due to relatively smaller spin flip barrier of these soft ferrites. The relaxation times have been computed for various temperatures and the results have been compared with those predicted by stationary Markoff spin flip process. The difference in results obtained through different techniques has been discussed. The spectral distribution is found to depend sensitively on microstructure.