Synthesis and characterization of oleic acid coated Fe–Mn ferrite based ferrofluid

Mn substituted Fe₃O₄ ferrite based ferrofluids were synthesized successfully and their structural and magnetic characteristics investigated. The two step method of synthesis was adopted wherein as the first step Mn substituted Fe₃O₄ ferrite nanoparticles having the chemical formula Fe_1-xMn_xFe₂O₄, where x = 0.0 to 0.5 in steps of 0.1 were synthesized by chemical co-precipitation method. The ferrite nanoparticles were characterized for their structural information using X-ray diffraction (XRD) technique. XRD pattern confirmed the formation of single phase spinel structure and the nanocrystalline nature of the samples. These ferrite nanoparticles were then dispersed in kerosene using oleic acid as the surfactant. FTIR spectroscopy was used to confirm the presence of Fe–O bonds and other chemical substance adsorbed on the surface of the particles. Magnetic measurements of the synthesized hydrocarbon based ferrofluids was carried out using Vibrating Sample Magnetometer (VSM) and Electron Paramagnetic Resonance (EPR) spectroscopy at room temperature. Magnetic parameters such as saturation magnetization, coercivity and remanence were evaluated from the M-H curve and the superparamagnetic behavior characteristic of magnetic nanoparticles was confirmed, which has also been observed from the EPR spectra recorded at room temperature.