A facile route to synthesis Ni_xFe_1−xFe₂O₄ ferrofluids with optimal rheological and magneto-optical properties

This study presents an easy method for synthesizing ultrafine Ni_xFe_1–xFe₂O₄ nanoparticles with adjustable composition (x = 0–.8), followed by their stabilization into ferrofluids. Structural identification of the crystalline structure, lattice points, and grain boundaries from the broadened diffraction peaks reveal an average crystalline size of the nanoparticles as 10–16.5 nm. Transmission electron microscopy images reveal spherical magnetite nanoparticles with a particle size ranging from 6 to 13 nm, consistent with diffraction studies. In ferrofluids, the Ni_xFe_1–xFe₂O₄ nanoparticles are stabilized in kerosene with oleic acid, a surfactant. Absorbance data of the ferrofluids is seen in the 200–400 nm wavelength region of UV–vis spectra. The magnetic properties of the samples are probed using a Superconducting Quantum Interference Device. The synthesized samples exhibit superparamagnetic behavior at room temperature (300 K). The saturation magnetization of the samples decreases with an increase in Ni composition (x = 0–.8), ranging from 54 to 28 emu/g. This study explores the magnetic and magneto-optical properties of Ni_xFe_1–xFe₂O₄ ferrofluids. Magneto-viscosity of ferrofluids is also studied, and the final application of such ferrofluids in data storage, catalysis, and biomedical applications is discussed.