محسن محرابی

This work's main purpose is to investigate the effect of Gd3+ substitution on the structural, cation distribution, morphological, and magnetic characteristics of cobalt ferrite nanostructures. The nanostructures were synthesized through the sol-gel auto combustion technique. X-ray diffraction (XRD) analysis with the Rietveld refinement through the MAUD program confirmed a single-phase spinel structure for lower contents of Gd3+. However, for higher concentrations, a trace of second phase GdFeO3 was evident. The crystallite size reduction from 17 nm to 11 nm with Gd3+ doping confirmed the formation of nanocrystalline Co-Gd ferrite. Cation distribution was another parameter inferred from the experimental data of XRD analyzed by the MAUD program. FTIR spectra confirmed the formation of spinel structure through two prominent vibrational modes observed at the desired wavelength range. FESEM analysis confirmed the data obtained from the XRD about the structure and morphology of the nano samples. Saturation magnetization (MS) of the nano samples evaluated at 10 K showed a decreasing behavior from 94 emu/g to 86 emu/g by Gd3+ doping, while a fluctuating trend of MS was observed at room temperature. Coercive field (HC) evaluated at 10 K reached a maximum value of about 1145 kA/m for the sample CoFe1.96Gd0.04O4, and then it decreased. At the same time, HC experienced no considerable change at 300 K. The possible concepts attributed to such a trend of HC were also investigated. Overall, the significant impact of Gd3+ doping on the cobalt ferrite nanoparticles causes Gd-Co ferrite to have a desirable capacity of permanent magnet materials and storage of information with high density. As a result, this ferrite may be a proper candidate to be utilized, especially at lower temperatures.