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

Abstract

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 °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.