Synthesis of Fe1-xCoxFe2O4 (x=0.0, 0.1) based ferrofluids and their structural, optical and magnetic investigations

Ferrofluids of magnetite nanoparticles having the formula Fe1-xCoxFe2O4 (x = 0.0, 0.1) have been prepared using chemical co-precipitation method. Oleic acid has been incorporated during the synthesis process and the nanoparticles are dispersed in kerosene using ultrasonicator to yield the desired ferrofluids. XRD measurements on the dried nanopowder confirm the spinel structure of the synthesized samples. The crystallite size of the samples is calculated from the most intense (311) peak of the diffraction pattern using Scherrer formula. The variation of 4sin theta vs beta cos theta from the Williamson Hall relation has been plotted in order to take into account the effect of lattice strain. The FTIR spectra of the pure and substituted Fe3O4 nanoparticles confirm the formation and successful surface functionalization of the Fe1-xCoxFe2O4 based ferrofluids. The microstructural studies have been carried out using FESEM and the particle size are found to be in the range 16 nm. The optical energy band gap of the samples is obtained from UV-Vis spectroscopy using the Tauc plot. The magnetic properties are investigated using vibrating sample magnetometer (VSM) and confirm the superparamagnetic nature of the prepared ferrofluids.