Formation of γ-Fe2O3 hierarchical nanostructures at 500 °C in a high magnetic field

Three-dimensional (3-D) hierarchical nanostructures of γ-Fe2O3 are prepared by a solvothermal process combined with subsequent thermal treatment in air at 500 or 350 °C with the aid of a high magnetic field. The experimental results indicate that γ-Fe2O3 instead of α-Fe2O3 forms in air at 500 °C in a 12 T field. The products are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The magnetization curves measured at room temperature exhibit superparamagnetic characteristics.