Amplification of magnetoresistance and Hall effect of Fe 3 O 4 – SiO 2 – Si structure

In this paper, we report the magnetoresistance and the Hall effect in the Fe3O4–SiO2–Si structure. Single phase magnetite films were deposited on n-type silicon substrates using laser molecular beam epitaxy. When the temperature is increased beyond 230 K, the resistance drops rapidly because the conduction path starts to switch from the Fe3O4 film to the inversion layer underneath the native SiO2 via thermally assisted tunneling. A large negative magnetoresistance is observed at about 230 K, and this maximum shifts to higher temperature with increasing film thickness. Hall effect data of the structure show that the carriers are holes above the channel switching temperature. Our results confirm that the large magnetoresistance at 230 K originates from the amplification of the magnetoresistance of the magnetite in the Fe3O4–SiO2–Si structure. © 2009 American Institute of Physics