Cr3+ and Al3+ co-substituted zinc ferrite: Structural analysis, magnetic and electrical properties

In this contribution we attempt to trace a correlation between structural features and physical properties of Cr–Al co-substituted zinc ferrite. Trivalent cations subtitution in the B sublattice weaken both A–B and B–B interactions simultaneously and hence the collinear ferrimagnetic structure not be so strongly affected. According to literature, the mechanism by which a third metal changes the properties of these complex systems is still a matter of controvers. Nanocrystalline powders of chromium and aluminum co-substituted zinc ferrites with general formula ZnFe2−2xCrxAlxO4 (0⩽x⩽1) have been synthesized for the first time. Using the sol-gel auto-combustion technique and the tartaric acid as combustion-complexion agent, materials with spinel mono-phase cubic spinel structure were successfully prepared. The materials were characterized by IR, XRD, SEM and 57Fe Mössbauer spectroscopy. The crystallite size estimated by Scherrer formula has been found in the range of 16–69nm. The experimental results combined with those obtained from a mathematical model suggested that all compounds have a mixed ionic distribution. Moreover, relationships between the structure features and the electric and magnetic properties have been established. The magnetic measurements showed that the hysteresis losses and the magnetization at 10 KOE linearly decreased when the Cr–Al content in Zn ferrite increased. The results obtained in dielectric study showed very low values of dielectric loss at frequencies over 1MHz.