Spin fluctuations in Co_0.5Zn_0.5Fe₂O₄ using the Mossbauer effect

Abstract

Mossbauer measurements in Co_0.5Zn_0.5Fe₂O₄ with 14.4 keV γ-rays from Fe⁵⁷ are reported. The spectra, in the temperature range from 90 to 455 °K, show features characteristic of relaxation effects. The shape of the spectra is related to the dynamical properties of the spins using a stochastic model for spin fluctuations. The overall agreement of the experimental data with computed shapes is satisfactory. There is no significant change in the value of relaxation time in the temperature range between 90 and 387 °K, and the change in the shape of the spectrum is mainly due to an increase in the value of s (the spin population parameter), and a decrease in the value of δ. A significant difference in the transition temperatures, as determined by neutron diffraction and the Mossbauer effect, can be explained to be due to the effect of relaxation on the shape of the Mossbauer spectrum. The presence of the relaxation effect is attributed to the influence of Zn²⁺ ions.