Pulsed laser deposition of Sr2FeMoO6 thin films grown on spark plasma sintered Sr2MgWO6 substrates

Sr2FeMoO6 (SFMO) films were deposited on polycrystalline spark plasma synthesized Sr2FeMoO6 (SMWO) substrates. Films were grown using pulsed laser deposition at temperatures (T-dep) between 720 degrees C and 820 degrees C in a vacuum environment of pressure P-dep = 10(-6) mbar (0.1 mPa); after deposition they were cooled either in a pressure P-cool = P-dep or P-cool = 10(-4) mbar (10 mPa) O-2. Despite the use of an isostructural substrate, the growth and cooling conditions play the primary role in determining details of the films' structures and properties, similarly to single-crystals. Grazing x-ray and electron back-scatter diffraction indicate that vacuum-cooled films were pure perovskite-structured SFMO exhibiting grainover-grain growth that aligned the perovskite sub-cells. SrMoO4 impurities were observed in the x-ray patterns for the oxygen-cooled films similarly to single-crystal substrates. Magnetic, electronic and magnetoresistive properties were all a function of growth and cooling environments. The Curie temperature and magnetization of the films increased with Tdep up to 800 degrees C. The vacuum-cooled films had low-resistivities with essentially metallic conductivity (small resistivity increases occurred at low-T),while the conductivity of oxygen-cooled films were consistent with variable range hopping. The oxygen-cooled films had higher low-field magnetoresistance effects at 5 K than the vacuum-cooled films, which seems consistent with SrMoO4 forming at grain boundaries. This work opens the route to tailor the electronic properties by engineering the grain boundaries in thin films.