Impact of Rare Earth Ions (Ce and Gd) on Structural and Magnetic Properties of Nanostructured Ni–Zn Ferrites

Present work focuses to investigate the impact of rare earth ions (Ce and Gd) on the structural and magnetic properties of nanocrystalline nickel-zinc ferrite. The nanoparticles of NiZnFeO, NiZnCeFeO, and NiZnGdFeO were synthesized by citric acid–assisted sol–gel method. The formation of cubic spinel structure without additional impurity peaks was confirmed by X-ray diffraction (XRD) pattern. The crystallite size of NiZnFeO (R = 0) and NiZnRFeO (R = Ce and Gd) nanoparticles was observed less than ~ 35 nm at sintering temperatures of ~ 300 to ~ 500 ℃. From magnetic measurements, the value of room temperature saturation magnetization of superparamagnetic NiZnFeO (R = 0) was found to be reduced with the doping of Ce and Gd ions from 44.19 ± 0.02 to 39.33 ± 0.03 emu/g and 35.18 ± 0.02 emu/g, respectively, at 300 ℃ and from 60.69 ± 0.04 to 54.11 ± 0.03 emu/g and 55.72 ± 0.04 emu/g, respectively, at 500 ℃. The detailed study of superparamagnetic relaxation in pure and rare earth-doped samples was performed by the thermal magnetization measurements under zero field cool (ZFC) and field cool (FC) processes. Mossbauer spectra revealed the absence of the quadrupole splitting for NiZnCeFeO at tetrahedral (A-site) and octahedral (B-site) sites which indicated cubic symmetry in the crystal structure. Although, the presence of negative asymmetry was observed in NiZnGdFeO-doped ferrite sample. Magnetic materials with superparamagnetic properties are desirable in various biomedical applications.