Structural and Magnetic Studies of Nano-crystalline Ferrites MFe2O4 (M = Zn, Ni, Cu, and Co) Synthesized Via Citrate Gel Autocombustion Method

Nano-crystalline ferrites with the chemical formula MFe2O4 (M = Zn, Ni, Cu, and Co) were synthesized via autocombustion route with citric acid as fuel. The ratio of citric acid to metal nitrate was taken as 1:1. The synthesized samples were characterized by powder X-ray diffraction and far-IR spectroscopy. The measured lattice constants and observed characteristic IR absorption bands of all samples were in good agreement with the reported values and showed the formation of a cubic spinel structure. The crystallite sizes of all samples were determined using high-intensity peaks and a W-H plot. The crystallite sizes of all samples were observed to be in the range of 16-26 nm with the least crystallite size of 16.8 nm for copper ferrite. All structural parameters were calculated using an experimental lattice constant and an oxygen positional parameter and correlated with far-IR results. Zinc and copper owing to their large cation radii showed the expansion of the lattice in view of the oxygen positional parameter. Magnetic measurements were carried out using a vibrating sample magnetometer at room temperature, and parameters such as saturation magnetization, coercivity, remanence, squareness ratio, and Bohr magnetons were calculated. Among all synthesized nano-ferrites, cobalt nano-ferrite showed the highest saturation magnetization of 41 emu/g, whereas zinc ferrite displayed a low saturation magnetization value of 12.87 emu/g.