Structural and magnetic study of Sm doped NiFe₂O₄ nanoparticles

NiFe_2−xSm_xO₄ (x = 0.0, 0.01, 0.025, 0.05, 0.075, 0.1) nanoferrites samples were prepared by sol–gel method. The structural properties of the samples were studied by X-ray powder diffraction, where the formation of a cubic spinel phase was confirmed. The lattice parameter and the particle size were determined by applying Rietveld refinement. A slight change in the lattice parameter was observed for Sm doped nanosamples. Whereas, the particle sizes were found to decrease with increasing Sm concentration (x) and have the highest value (42 nm) for pure NiFe₂O₄ nanoparticles. The magnetic properties were characterized using Mössbauer effect (ME) spectroscopy and vibrating sample magnetometer (VSM). ME spectroscopy was used to study the distribution of cations in tetrahedral (A) and octahedral [B] sites of the nanoparticles and the degrees of inversion values were obtained. The saturation magnetization, coercivity and remanent magnetization were determined using VSM measurements. These magnetic parameters vary with Sm substitution and found to be mainly affected by the change in the cations distribution and particle sizes.