Autocombustion High-Temperature Synthesis, Structural, and Magnetic Properties of CoCrxFe2-xO4 (0 ≤ x ≤ 1.0)

CoCrxFe2-xO4 (0 <= x <= 1.0) was synthesized by sol-gel auto combustion method using nitrates of respective elements and by keeping 1:3 ratio of metal nitrate to citrate. Representative sample was investigated by thermogravimeter/differential thermal analyzer (TG/DTA); then, all samples were annealed at 500 degrees C for 4 h. The broad peaks in the X-ray diffraction patters (XRD) and evaluation of transmission electron microscopy (TEM) indicate a fine particle nature of the particles. Scanning electron microscopy (SEM) analysis and EDAX indicated that the samples were homogeneous and had the expected Fe-Co-Cr ratios. The lattice parameter, bulk density, and particle size are decreased, whereas the X-ray density, specific surface area, and porosity tend to increase with increasing Cr3+ substitution. Cation distribution was estimated using XRD and by employing Bertaut method. Fourier transform infrared spectroscopy (FT-IR) is employed to determine the local symmetry in crystalline solids and to shed light on the ordering phenomenon. Saturation magnetization determined from vibrating sample magnetometer (VSM) decreases linearly with Cr3+ concentration, suggesting that the superexchange interaction Fe(A)-O-Fe(B) link is stronger than that for the Fe(A)-O-Cr(B) link. Coercivity in the Cr-doped cobalt ferrites was larger than that in pure CoFe2O4 compositions.