Cation distribution correlated with magnetic properties of nanocrystalline gadolinium substituted nickel ferrite

Nano crystalline NiFe2−xGdxO4 (0.0≤x≤0.4) ferrite was prepared by citrate method. The samples were characterized with X-ray diffraction, FT-IR spectroscopy, TEM and magnetic measurements. The effect of Gd3+ cations substitution on structural, microstructural and magnetic properties of prepared nanoparticles was investigated. From Rietveld analysis, the system was found to be inverse spinel structure with Gd3+ residing on octahedral B-site 16c and the grain boundary, while Ni2+ occupying the B-site at both 16c and 16d. The lattice parameter (a) changes nonmonotonically, first increases then decreases with Gd doping content. The M-H and M-T relations had demonstrated a change in the magnetic moment and a ferrimagnetic-superparamagnetic transition in the ferrite system. For low temperature measurements, an increase in gadolinium content resulted in increasing the coercive field while the saturation of magnetization (Ms), first deceases then increases with Gd doping content. At room temperature Ms decreases with increasing Gd substitution.