Transport characteristics of magnetite thin films grown onto GaAs substrates

Magnetite thin films with a preferred (111) orientation have been deposited by reactive dc magnetron sputtering from a pure Fe target onto (100) GaAs substrates at 400 degreesC. The films show a clear Verwey transition in both the magnetization and sheet resistance as functions of temperature. For films deposited onto semiconducting n-type GaAs substrates, we have obtained asymmetric current-voltage (I-V) characteristics with a Schottky diodelike behavior in forward bias. Activation energy plots of the I-V data as a function of temperature indicate a barrier height of 0.3-0.4 eV. This does not take into account the contribution from tunneling across the narrow depletion layer in these junctions, so should be considered a lower bound to the actual Schottky barrier height. Our work points to the potential integration of half-metallic magnetite with GaAs-based heterostructures for spin-electronic devices. (C) 2004 American Institute of Physics.