The fabrication and magnetic properties of nanowire-like iron oxide

Nanowire-like iron oxides (α-Fe 2 O 3 , Fe 3 O 4 and γ-Fe 2 O 3 ) of diameter about 200 nm and length up to 8 µm 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 Fe 3 O 4 wires, reduced transition temperature in α-Fe 2 O 3 and Fe 3 O 4 wires, and superparamagnetism in γ-Fe 2 O 3 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.