IMPROVEMENT OF SUPERCONDUCTIVITIES OF THIN YBA2CU3OY FILMS BY THE BUFFER PRBA2CU3OY LAYER

Using an off-axis rf sputtering configuration, we prepared in situ hig h-T(c) bilayer YBa2Cu3O7-y/PrBa2Cu3Oy (YBCO/PBCO) films. Two stoichiom etric targets of YBCO and PBCO were mounted face to face in the sputte ring system. The sputtering gas was a mixture of Ar and 02 (3:7) and t he substrate was MgO (001). We found the buffer PBCO layer is very eff ective in improving the superconductivity of the as grown YBCO/PBCO fi lms. The resistive transition gets narrower in a magnetic field parall el to the ab plane and gets broader in a magnetic field parallel to th e crystal c axis as the thickness of the YBCO layer becomes thinner. T hese results suggest an anisotropic flux pinning in the bilayer YBCO/P BCO films.