Magneto-transport in Fe$_{3}$O$_{4}$/Nb:SrTiO$_{3}$ schottky junction diode

Among the half metallic ferromagnets, Fe$_{3}$O$_{4}$ is of particular interest because of its half metallicity, high curie temperature and a charge ordering transition at 120K (popularly known as Verwey transition (T$_{V}))$. These materials are also expected to show 100{\%} spin polarization. In view of these fascinating properties, we studied temperature dependent transport, magnetic, structural and interface characteristics of epitaxial schottky junctions between Fe$_{3}$O$_{4}$ and Nb:SrTiO$_{3}$ (with different Nb concentrations). Epitaxial thin films of Fe$_{3}$O$_{4}$ were grown on Nb:SrTiO$_{3}$ substrates by PLD technique. The films show epitaxial growth along (100)-axis direction. We also performed HR-TEM and EELS study to ensure a better quality interface. In the temperature range above T$_{V}$, 300K-130K, the I-V characteristic shifts towards higher forward bias voltage upon lowering temperature. On further decreasing temperature (below T$_{V})$, the trend is reversed. Junction parameters such as the Schottky barrier height (\textit{$\phi $}$_{B})$ and ideality factor (\textit{$\eta $}) are extracted using thermionic emission theory at all temperatures. These parameters show interesting and systematic trends above and below T$_{V}$. From the magnetic field dependence of non linear I-V characteristics data, a spin polarization of $\sim $80{\%} is estimated for the magnetite electrode at T$_{V}$.