The fabrication and magnetic properties of nanowire-like iron oxide

Nanowire-like iron oxides (alpha-Fe2O3, Fe3O4 and gamma-Fe2O3) of diameter about 200 nm and length up to 8 mum were assembled into anodic aluminium oxide templates through electrodeposition followed by a heat-treating process. These wires have polycrystalline structures and consist of fine particles whose magnetic moments have preferred orientations in the templates. Some unique magnetic properties, such as perpendicular magnetic anisotropy in Fe3O4 wires, reduced transition temperature in alpha-Fe2O3 and Fe3O4 wires, and superparamagnetism in gamma-Fe2O3 wires, were observed. The properties can be understood by their unique structures induced by reduced dimension and the competition of the shape and crystalline anisotropy.