Magnetite (Fe3O4) nanoparticles were prepared by a simple precipitation method between Fe(NO3)3·9H2O and FeCl2·4H2O. The effects of surfactant, temperature, time, solvent and magnetic field on the morphology and particle size of the products were investigated. The magnetic properties of the product were investigated using an alternating gradient force magnetometer (AGFM). The Fe3O4 nanoparticles exhibit ferrimagnetism behaviour at room temperature, with a saturation magnetization of 38.7 emu/g and a coercivity of 0.78 Oe. Such a low coercivity is attributed to superparamagnetic (which is a size dependent) behaviour of Fe3O4 in nanoparticle scale.
