Structural characterization and enhanced magnetic and dielectric properties of Ce3+ substituted Co–Cr–Fe–O nano-ferrites synthesized using sol–gel method

Unique and novel size dependent structural and physical properties with wide applications attracts the interest of scientific community to study of rare earth doped spinel ferrites. In the present investigation, sol–gel auto-ignition process was employed to synthesize the compositions CoCr0.2CexFe1.8−xO4 (x = 0.0, 0.025, 0.050, 0.075, 0.1) sintered at significant temperature of 800 °C for 6 h. The structure and phase purity of the samples was analysed by using X-ray diffraction (XRD) technique. Increasing cerium concentration enhances the lattice lengths of cubic spinels from 8.3839 to 8.3965 Å. The cation distribution suggests that the Co2+ ions occupy octahedral–B site and larger Ce3+ ions replace smaller Fe3+ ions at octahedral-B sites. Fourier transform infrared spectra (FTIR) confirmed the metal–oxygen (M–O) stretching bonds at tetrahedral–A and octahedral–B sites confirming the spinel structure of the samples. Elastic parameters were determined from FTIR data and have been studied in the light of Ce3+ substitution. Surface morphology of the samples have been studied by using scanning electron microscopy and transmission electron microscopy which reveals the narrow size distribution with nanoparticles of size nearly 50 nm. Vibrating sample magnetometry (VSM) technique was employed to understand the magnetic behaviour of the samples, where the room temperature saturation magnetization was decreased from 72.07 to 65.86 emu/g and coercivity increased from 277 to 918 Oe with Ce3+ substitution. Frequency dependent dielectric parameters like Dielectric constant, dielectric loss and dielectric loss tangent shows decreasing trend with the increase of frequency. Substituting Fe3+ with Ce3+ reduced saturation magnetization and raised coercive field, suggesting suitability for permanent magnets.