Improved J/sub c/ of bilayer YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film structures

Critical-current (J/sub c/) measurements for YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO), Gd/sub 0.6/Ca/sub 0.4/Ba/sub 1.6/La/sub 0.4/Cu/sub 3/O/sub 7-/spl delta// (TX-GBCO) and TX-GBCO/YBCO bilayers were performed with transport measurements at different applied magnetic fields. The film samples were prepared by pulsed laser deposition and patterned as microbridges. The highest J/sub c/ (1.5/spl times/10/sup 6/ A/cm/sup 2/) at 75 K in 5 Tesla (Hllab) was observed for TX-GBCO/YBCO bilayers, which showed a 40% increase in J/sub c/ over YBCO under the same conditions. The bilayer samples possess a T/sub c/ at 90 K and display superconducting properties similar to YBCO. A possible mechanisms for the high J/sub c/ of bilayer YBCO films is discussed. Development of these bilayer and multilayer structures represents a promising new direction to improve the superconducting properties of YBCO since the TX-GBCO layer provide both protection against corrosion and a significant improvement in J/sub c/.