Structure and magnetic properties of ZnO coated MnZn ferrite nanoparticles

A comparative study of structural and magnetic properties of MnZn spinel ferrite (SF) and ZnO coated MnZn ferrite (ZF) nanoparticles (NPs) has been carried out. The as-prepared NPs show a single phase cubic spinel structure, with lattice parameter similar to 8.432 angstrom. However, alpha-Fe2O3 impurity phase emerge from SF particles when subjected to annealing at 600 degrees C in air. The weight fraction of alpha-Fe2O3 phase increases with increasing Mn concentration (9% for x=0.2 and 53% for x=0.6). On the other hand in ZF (x=0.2 and 0.4) NPs no trace of impurity phase is observed when annealed at 600 degrees C. The magnetic measurements as a function of field and temperature revealed superparamagnetic like behavior with cluster moment similar to 10(4) mu(B) in as-prepared particles. The cluster size obtained from the magnetic data corroborates well with that estimated from structural analysis. Present results on ZnO coated MnZn ferrite particles suggest that an interfacial (ZnO@SF) reaction takes place during annealing, which results in formation of Zn-rich ferrite phase in the interface region. This leads to deterioration of magnetic properties even in the absence of alpha-Fe2O3 impurity phase. (C) 2016 Elsevier B.V. All rights reserved.