Synthesis, characterization and studies on magnetic properties of nanocrystalline CoNb_yFe_2-yO₄ spinel ferrites

We have successfully synthesized Nb substituted cobalt ferrite nanomaterials (CoNb_yFe_2-yO₄, where y = 0.0, 0.01 and 0.02) via sol gel autocombustion method. The phase pure product is confirmed by powder XRD analysis. XRD studies allowed the determination of crystallite size by using the Scherrer formula. The calculated crystallite sizes are 42 nm, 31 nm and 25 nm for CoNb_yFe_2-yO₄ materials with Nb content, y = 0.0, 0.01, 0.02; respectively. The particle sizes obtained from SEM micrographs are in accordance with XRD crystallite sizes. Saturation magnetization (M_s) values decrease from 81.75 emu/g to 71.21 emu/g for CoNb_yFe_2-yO₄ materials with Nb content, y = 0.0 and 0.02, respectively. The results have been interpreted on the basis of increased Nb contents along with size and surface effects.