Influence of Cr on structural, spectroscopic and magnetic properties of CoFe2O4 grown by the wet chemical method

Abstract

The Cr doped CoFe2O4 nano crystalline ceramics are synthesized using wet chemical method. The structural, morphological, functional, spectroscopic and magnetic properties of pure CoFe2O4 and Cr doped CoFe2O4 are characterized by XRD, FESEM, FTIR, Raman, Mössbauer spectroscopy and M-H hysteresis loop. The X-ray diffraction (XRD) patterns of undoped (x = 0) and doped (x≠ 0) samples reveal the formation of single phase cubic spinel structure. The lattice parameters and cation distribution between tetrahedral (A) and octahedral (B) sites of the samples (AB2O4) were obtained by Rietveld refinement of XRD patterns. The FESEM micrographs exhibit dense micro structure with small voids. The energy dispersive x-ray studies confirm the presence of Cr in CoFe2O4. The FTIR spectrum confirms that the peaks corresponding to the metal-oxygen bonds have shiftedtowards higher wavelength region. Raman spectrum exhibits broad peaks which confirm the existence of local disorder due to the inter-site cation migration between tetrahedral and octahedral sites. The Mössbauer spectroscopy reveals that the magnitude of magnetic hyperfine field of tetrahedral site (HA) and octahedral site (HB) decreases with increase in Cr doping in CoFe2O4 and that the decrease is more rapid in tetrahedral site (HA) compared to that in octahedral site (HB). And also confirm that the magnetic hyperfine fields (Bhf) are smaller relative to pure cobalt ferrite representing that super exchange interaction which is decreases as the Cr concentration increases. The magnetization studies reveal a decrease in the saturation magnetization (Ms) of CoFe2O4with increase in Cr substitution. A similar and non-monotonic variation of coercivity (Hc) and magneto crystalline anisotropy (K) suggests that Hc is mainly determined by K.