Rare-Earth Doped Ni-Co Ferrites Synthesized By Pechini Method: Cation Distribution And High Temperature Magnetic Studies

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 Fd 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.