Rare-earth doped Ni–Co ferrites synthesized by Pechini method: Cation distribution and high temperature magnetic studies

Abstract The present work was focused on the effect of rare earth doping on the structural and magnetic properties of Ni–Co ferrite materials with general chemical formula Ni0.5Co0.5Fe1.98R0.02O4 (R = La, Nd, Sm, Gd, Dy). All the ferrites, synthesized by the Pechini method, possess cubic symmetry with F d 3 _ m space group. A very small change in lattice parameter has been observed with rare earth (R3+) doping. The cation distribution between the tetrahedral (A-site) and octahedral sites (B-site), as estimated by X-ray diffraction analysis (XRD) revealed that the R3+, Co2+ and Ni2+ ions have migrated to the octahedral site. Room temperature magnetization results, obtained from Vibrating Sample Magnetometer (VSM) measurements, showed that saturation magnetization of rare-earth doped ferrites is strongly dependent on magnetic moment of rare earth ion. The coercivity increases with increase in the atomic number of rare-earth ion, which could be justified on the grounds of the stability of spin-orbital coupling that controls the magnetic anisotropy in ferrites. The results further suggest that the Curie temperature is dependent on lattice parameter and hence inter-atomic distance between magnetic ions.