Magnetic Properties of Magnetite Nanoparticles Synthesized by Oxidative Alkaline Hydrolysis of Iron Powder

Abstract

The black magnetic nanoparticles (MNPs) of magnetite (Fe₃O₄) were synthesized by oxidative alkaline hydrolysis of the atomized iron powder precursor. The synthesized particles prepared at different precipitation temperatures were characterized using X-ray powder diffraction (XRD), the Brunauer–Emmett–Teller (BET) method and transmission electron microscopy (TEM). Their magnetic properties were examined using a vibrating sample magnetometer (VSM), measurement of the initial magnetic susceptibility, acquisition of the isothermal remanent magnetization (IRM) and alternating field (AF) demagnetization of the acquired IRM. The results showed that the sizes of MNPs depended upon the precipitation temperature, which affected the magnetic susceptibility, magnetic hysteresis properties and remanent properties of the synthesized MNPs. The maximum grain size, magnetic susceptibility and magnetic hysteresis properties were obtained from the MNPs synthesized at a precipitation temperature of 70°C. The MNPs prepared by this method exhibited a cubo-octahedral structure with average particle sizes of 25-70 nm. Room temperature magnetic hysteresis properties confirmed the ferromagnetic behavior of stable single domain particles with saturation magnetization of 11.64-77.45 emu/g, remanent magnetization of 1.28-15.769 emu/g, and coercivity of 112.42-158.03 G.