Transport and magnetic properties of epitaxial and polycrystalline magnetite thin films

The transport and magnetic properties of magnetite $({\mathrm{Fe}}_{\mathrm{3}}{\mathrm{O}}_{\mathrm{4}})$ thin films grown epitaxially on single crystal MgO(100) and ${\mathrm{SrTiO}}_{\mathrm{3}}\text{(100)}$ substrates, and with multiple grain orientations on polycrystalline ${\mathrm{SrTiO}}_{\mathrm{3}}$ substrates, have been investigated. The films are grown using pulsed laser deposition and their epitaxial quality determined using ion channeling measurements. Transport and magnetic studies of ${\mathrm{Fe}}_{\mathrm{3}}{\mathrm{O}}_{\mathrm{4}}$ films as a function of thickness and morphology suggest that epitaxial strain and growth defects affect the width and temperature of the Verwey transition. In addition, these factors also significantly influence the magnetic coercivity of the films. The low-field magnetoresistance (MR) behaviors of epitaxial and polycrystalline films as a function of temperature have been compared and they were found to be quite similar, suggesting very small contribution to the MR from grain boundaries.