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

Abstract Nano crystalline NiFe_2-xGd_xO₄ (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 (M_s), first deceases then increases with Gd doping content. At room temperature M_s decreases with increasing Gd substitution.