Synthesis, structure and magnetic properties of iron-doped tungsten oxide nanorods

Iron-doped tungsten oxide nanorods of 20–30 nm in diameter and 60–2000 nm in length have been prepared by an arc discharge route using W as cathode and a mixture of Fe and NiO as anode, in which NiO serves as oxygen source. The characteristics of the nanorods were investigated systematically by using X-ray diffraction, transmission electron microscopy, energy dispersive spectra, X-ray photoelectron spectroscopy, and superconducting quantum interference device magnetometer. The nanorods were mainly composed of tungsten, iron and their oxides. The iron-rich phase in the nanorods exhibits soft ferromagnetic behaviors with zero coercivity and zero remanence and a decreased Curie temperature of 1000 K. Heat-treatment of the sample in air induces oxidation of elemental Fe, resulting in the reduction of the magnetization.