Magnetic and transport properties of nanocomposite Fe/Fe3-δO4 and Fe3-δO4 films prepared by plasma-enhanced chemical vapour deposition

Reflective, pinhole-free Fe/Fe3O4 and Fe-3-delta O-4/Fe2O3 nanocomposite films were obtained by reacting iron pentacarbonyl, Fe(CO)(5), in an inductively-coupled radio frequency glow discharge reactor. The conductivity of the Fe-x/(Fe3O4)(1-x) (x > 7%) composite films exhibits metallic characteristics and the conductivity decreases as the alpha-Fe content decreases. The metal-to-insulator transition temperature of the Fe-x/(Fe3O4)(1-x) (x similar to 0.07)) films shifts to a higher temperature as compared with Fe-3-delta O-4 due to the increased conductivity from alpha-Fe. The magnetization versus temperature (M-T) curves show the transition temperature ranging from 95 to 136 K, corresponding to the Verwey temperature, which is dependent on the film composition. The Fe3-delta O-4 film exhibits a negative magnetoresi stance of about 4% and 8% at room temperature and 80 K, respectively.