Effect of Fe2O3 on the transport and magnetic properties of half metallic Fe3O4

We present a systematic study of the transport and magnetic properties of half metallic Fe3O4 films grown on Si (100) substrates with a Fe2O3 buffer layer using electron beam deposition technique. Transmission electron microscope images show the presence of small grains that are well separated by grain boundaries in our polycrystalline films. We observed that the Verwey transition does not appear for our Fe3O4 films and tunneling of spin polarized electrons across grain boundaries dominates the transport properties of the films. Magnetic measurements show a reduced magnetization in our films which does not saturate even at high fields. Coercivity of the films increases with decreasing temperature, suggesting the existence of additional anisotropy at low temperatures. Magnetoresistance curves show linear behavior at high fields which may be attributed to second order tunneling through intermediate states in the grain boundaries. At lower fields, the magnetoresistance behavior is governed by direct tunneling. (C) 2006 American Institute of Physics.