Cation distribution in nanocrystalline NixZn1 − xFe2O4 spinel ferrites

We have studied the cation distribution over the tetrahedral and octahedral sites in the spinel structure of nanocrystalline Ni x Zn 1 − x Fe 2 O 4 ferrites prepared by spray pyrolysis. 57 Fe Mössbauer spectroscopy data for the ferrites demonstrate that, depending on the composition of the materials, the tetrahedral site may accommodate only Fe 3+ (inverse spinel, x ≥ 0.4) or both Fe 3+ and Zn 2+ cations (mixed spinel, x = 0 and 0.2), which accounts for the fact that the composition dependence of the unit-cell parameter for the ferrites deviates from Vegard’s law.