Enhanced tunneling magnetoresistance of Fe3O4 in a Fe3O4-hexabromobenzene (C6Br6) composite system

Magnetotransport of Fe3O4-hexabromobenzene (C6Br6) composite has been studied. Powders of C6Br6 and Fe2O3 nanoparticles were mixed together. They were annealed in hydrogen flow. There was a phase transformation from Fe2O3 to Fe3O4 after annealing. Giant negative magnetoresistance (MR) was observed at room temperature and the MR ratio is about 13.4% in an applied field of 5 T. The maximum MR ratio is 21.5% at 130 K. The temperature dependence of the resistivity exhibits characteristics of intergranular tunneling in the samples. The enhancement of the MR ratio is attributed to the fact that the C6Br6 can act as barrier material and, more importantly, can prevent the oxidation of the surface of Fe3O4, which is believed to alter the half-metallic state at the surface.