Effect of substrate-twin-induced microstructure on transport properties of epitaxial Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub x/ films in a magnetic field

The role of substrate-induced microstructure on transport properties in c-axis-oriented epitaxial Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub x/ films grown on LaAlO/sub 3/ and SrTiO/sub 3/ has been studied. For a magnetic field parallel to the Cu-O planes, resistivity and the critical current density, J/sub c/, have been measured as a function of angle theta between the applied field and the direction of transport current. Resistivity dips and enhancement of J/sub c/ were observed for magnetic fields applied parallel to the substrate twins in LaAlO/sub 3/ in high fields (>or=2 T). For films on SrTiO/sub 3/, resistivity and J/sub c/ were Lorentz-force independent.<
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