Synthesis, M ssbauer Spectra and Magnetic Properties of Quasi-One-Dimensional Fe3O4Nanowires

Quasi-one-dimensional Fe 3 O 4 nanowires in diameter of about 200 nm were assembled into anodic aluminium oxide templates via electrodepositing and heat-treating processes. The nanowires have a polycrystalline spinel structure with a = 8.317 Å, and each nanowire is composed of fine Fe 3 O 4 crystallites with size of about 30 nm. The magnetic moments of Fe 3 O 4 crystallites in nanowires have a preferred orientation leaning to the wire axis but not parallel to the wire axis. Mössbauer spectra (MS) were used to verify the presence of Fe 3 O 4 further and the existence of superparamagnetic particles in nanowires. A perpendicular magnetic anisotropy was observed obviously. Temperature dependence of the magnetic moments ( M – T ) shows that the Verwey transition for the Fe 3 O 4 nanowires occurs at 50 K, and the behaviour of the M – T curve is different from that of other magnetite materials. These characteristic magnetic properties of Fe 3 O 4 nanowires are mainly due to the reduced dimension and the configuration of preferred orientation in the nanowires caused by the shape anisotropy.