Amplification of magnetoresistance of magnetite in an Fe3O4-SiO2-Si structure

Film of Fe(3)O(4) was prepared with laser molecular beam epitaxy deposition on a Si substrate with a native SiO(2) layer. When the temperature is increased above 250 K, the resistance drops rapidly because the conduction path starts to switch from the Fe(3)O(4) film to the inversion layer underneath the SiO(2) via thermally assisted tunneling. A greatly magnified low field negative magnetoresistance of Fe(3)O(4) is observed at 280 K. The effect is similar to a metal-oxide-semiconductor field-effect transistor. The magnetoresistance becomes positive with further increase in the magnetic field due to the Lorentz force and other effects on the carriers in the inversion layer. (C) 2008 American Institute of Physics.