Attestation in self-propagating combustion approach of spinel AFe ₂ O ₄ (A = Co, Mg and Mn) complexes bearing mixed oxidation states: Magnetostructural properties

Spinel type nano-sized ferrite compounds AFe ₂ O ₄ (A = Co, Mg and Mn) have been successfully prepared by self-propagating combustion method using glycine as fuel at 400 °C under air atmosphere for 4 h. The crystal structure, chemical composition, morphology and magnetic properties of the synthesized samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Energy dispersive X-ray, Scanning and Transmission electron microscopy and vibrating sample magnetometer. The chemical reaction and role of fuel on the nanoparticles formation were discussed. The XRD pattern of the synthesized samples shows the formation of pure phase with average crystallite size of 97, 57 and 98 nm from Scherrer formula and 86, 54 and 87 nm from Williamson and Hall (W-H) formula respectively. FTIR absorption spectra revealed that the presence of strong absorption peaks near 400-600 cm ^-1 corresponds to tetrahedral and octahedral complex of spinel ferrites. The relative concentrations of electronic states of elements such as cobalt (Co ²⁺ and Co ³⁺ ), iron (Fe ²⁺ and Fe ³⁺ ) and manganese (Mn ²⁺ and Mn ³⁺ ) oxidation states were studied from XPS and it is found that 55% of Fe ions are in Fe ²⁺ state and the remaining is in Fe ³⁺ state and thus the cationic distribution of Fe ions occurred in both tetrahedral and octahedral sites. SEM analysis indicates the presence of pore like morphology which is nearly homogenous because of combustion process. EDS analysis confirms the presence of elements in the ferrite samples. By replacing the active 'A' site cations in AFe ₂ O ₄ (A = Co, Mg and Mn) samples show the different magnetic properties. The parameters like saturation magnetization, coercivity and remnant magnetization obtained from M-H loops are studied in room temperature.