Rietveld refinement, morphology and superparamagnetism of nanocrystalline Ni0.70-xCuxZn0.30Fe2O4 spinel ferrite

The crystallographic phase and particle size of Cu2+ substituted Ni-Zn spinel ferrite prepared by nitrate-citrate route was evaluated using XRD and TEM techniques respectively. Rietveld refined XRD patterns revealed the cubic spinel phase with Fd-3m space group. The average particle size estimated from TEM image revealed the nanocrystalline nature which matches well with the crystallite size determined by XRD data. High resolution TEM exhibited the lattice fringe patterns which correspond to cubic spinel structure. The samples were characterized by M-H plots and Mossbauer spectra at room temperature. Magnetization curves exhibited typical superparamagnetic nature of samples which is in good agreement with that of Mossbauer measurements. The obtained coercive field is low which may make these materials suitable for soft magnetic device applications.