Fascinating improvement in physical properties of Cd/Co nanoferrites using different rare earth ions

Cadmium-cobalt-rare-earth nanoferrite samples of composition Cd_0.7Co_0.3Fe₂O₄ and Cd_0.7Co_0.3R_0.05Fe_1.95O₄ (R = Ce, Sm, Gd, Er) were prepared by citrate auto combustion method. All samples were characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Micrographs (HRTEM), Energy Dispersive X ray Spectroscopy (EDAX) and Atomic Force Microscope (AFM). XRD confirmed the formation of cubic spinel structure with the appearance of small peaks designated as secondary phases. The average crystallite sizes were found to be between 40.3 and 22.1 nm for pure and Gd doped samples respectively. The magnetic properties were studied by carrying out the hysteresis of the investigated samples at room temperature and at 100 K. The magnetic parameters, such as the saturation magnetization, coercivity H_c, squareness and loop area are markedly affected by increment of rare earth ions at the expense of Fe³⁺ ions in a spinel structure. The increase in magnetization of the nano ferrite samples at 100 K, may be clarified by annihilation of a nonmagnetic layers (surface dead layers) due to the rare earth doping. Greater than nearly nine-fold increase in coercivity was observed in pure and Ce, Sm doped compared to the Gd and Er samples. The data for H_c, M_s and M_r of lanthanide doped ferrites suggest their suitability in applications like magnetic targeting and separators.