Epitaxial growth of high quality SrFeO₃ films on (001) oriented (LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7

The growth of strontium ferrite SrFeO₃ films with a stoichiometry of (1:1:3) is challenging as the unstable Fe⁴⁺ oxidation state favors the formation of O vacancies. Here, we report the layer by layer growth of SrFeO₃ on (001) oriented (LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7 using ozone assisted molecular beam epitaxy. Upon cooling from room temperature, the film's resistivity decreased from 750 μΩ cm to 150 μΩ cm, as low as the best single crystals, with two identifiable transition points near 110 K and 60 K in resistivity measurements, being hysteretic between cooling and warming through the 60 K transition. During various annealing steps, the low temperature resistivity changes by orders of magnitude, accompanied by an increase in the c-axis lattice parameter. The hysteresis near 60 K persists for a wide range of annealing conditions. We have identified conditions under which changes due to annealing can be reversed. We attribute changes in resistivity and the out of plane lattice parameter to the reversible movement of oxygen ions in the lattice. SrFeO₃ may be a promising material for resistive memory applications based upon the control of oxygen vacancies.