Abstract
Rare earth Sm and Ce co-substituted nano crystalline cobalt ferrite, CoFe2-x-ySmxCeyO4 (x = y = 0.00, 0.5, 0.1, 0.12 and 0.25) have been synthesized by sol-gel combustion method to study structural, morphological and magnetic properties. X-ray diffraction (XRD) revealed the spinel structure with a secondary phase of RE2O3 for higher molar concentration of rare earth ions. Williamson-Hall equation used to determine crystallite size and strain produced. An increase in specific surface area and Strain, while a decrease in the crystallite size were observed with increasing Sm and Ce concentrations. Scanning electron microscopy (SEM) micrographs showed inhomogeneous grain distributions with some agglomerates, an average grain size was found to be 0.15 μm. Energy dispersive x-ray spectroscopy (EDAX) confirmed the stoichiometry of the samples. Surface morphology studies were carried out by Transmission electron microscopy (TEM) studies which corroborates the presence of agglomerations in the sample. Fourier transform infrared spectroscopy (FTIR) spectra confirmed the spinel phase by showing two frequency bands υ1 in frequency range 580-559 cm−1 and lower frequency band υ2 at 392-372 cm-1. The force constants calculated for tetrahedral position was found to be more than that of octahedral position. Based on structural properties a cation distribution was proposed. Vibrating sample magnetometer (VSM) technique at room temperature used to study the magnetic properties, saturation magnetization (Ms), coercivity (Hc), anisotropy constant and initial permeability. Ms and Hc were found decreasing with increasing concentration of rare earth ions which has been attributed to weakening of A-B interaction, due to decrease in particle size and surface effect. Yafet-Kittle (YK) angle was found increasing with rare earth concentrations. The Ms and Hc of cobalt ferrite particles can be tailored for various applications.
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•Substitution RE (Sm and Ce) has led to micro strain in the crystal.•Cation distribution has been proposed.•Surface effect played an important role in magnetization.•YK angle increased with RE (Sm, Ce) concentration.