Magnetic characterization of γ-Fe2O3 nanoparticles fabricated by aerosol pyrolysis

The magnetic properties of γ-Fe2O3 nanoparticles prepared by spray pyrolysis of dilute solutions of Fe(III) and Fe(II) salts have been investigated using both magnetic measurements and Mössbauer spectroscopy. The most outstanding magnetic features are the strong reduction of the saturation magnetization compared with that of the bulk material, and the existence of magnetic hysteresis up to the highest field used (55 kOe) in both the M(H) loops and the zero-field cooling-field cooling M(T) curves. The magnetic particles exhibit superparamagnetic behavior at room temperature. From the evolution of the ferromagnetic ratio, MR/MS, with temperature we have determined the distribution of the blocking temperatures that can be described properly with a log–normal distribution, which allows the determination of mean blocking temperatures 〈TB〉 and mean particle volumes.