Magnetoresistance and magnetic properties of epitaxial magnetite thin films

The magnetotransport and magnetic properties of epitaxial (Formula presented) thin films grown on (001)-oriented MgO substrates by pulsed-laser deposition have been investigated. The magnetoresistance (MR) exhibits a peak around the Verwey transition (Formula presented) as has also been reported previously for single crystals. Additionally, we have observed that the MR increases monotonically below 100 K with decreasing temperature. MR values as high as 32% have been observed for a 6600-Å-thick film at 60 K under a 4-T field. The enhanced low-temperature MR is attributed to a magnetic-field-dependent activation energy for electron hopping transport. © 1997 The American Physical Society.