Structural and Magnetic Studies of Rare-Earth Substituted Nickel Ferrites

Polycrystalline ferrites NiFe2O4 and NiFe1.99R0.01O4 (R=Sm, Gd, Eu, and La) samples were prepared by usual ceramic method. The structural and the magnetic properties of the samples were characterized by X-ray powder diffraction (XRD), Mossbauer Effect (ME) spectroscopy, and vibrating sample magnetometer (VSM). Indexed XRD patterns confirm the formation of pure cubic spinel phase. The lattice parameters (a) of the rare earth (R) doped samples were smaller than that of the pure Ni-ferrite. Mossbauer effect spectroscopy was used to study the distribution of cations in tetrahedral (A) and octahedral [B] sites of the spinel. The hysteresis loops indicated that the saturation magnetization and coercivity increased with R-substitution and appeared to be greatly affected by the nature of R ions. The obtained results are interpreted based on the rearrangement of cations between the A-site and B-site.