SUPERCONDUCTING YBA2CU3O7-X THIN-FILMS ON POLYCRYSTALLINE FERRITE FORMAGNETICALLY TUNABLE MICROWAVE COMPONENTS

Superconducting YBa2Cu2O7-x (YBCO) thin films with a surface resistanc e of 0.86 m Omega at 10 GHz and 76 K have been grown on polycrystallin e ferrite yttrium iron garnet (YIG) substrates. The chemical and struc tural mismatches between YBCO and YIG are solved by using a double buf fer layer of biaxially oriented yttria-stabilized zirconia (YSZ) and C eO2, when YSZ is deposited by an ion-beam-assisted-deposition techniqu e. The YBCO films are c axis oriented with an in-plane mosaic spread [ full width at half maximum of an x-ray phi-scan on (103) reflection] o f less than 8 degrees. The films have a superconductive transition tem perature above 88 K with a transition width less than 0.3 K, giving a critical current density above 10(6) A/cm(2) in self field at 75 K. At 75 K in an external magnetic field of 1 T perpendicular to the film s urface, the films maintain a critical current density over 2 X 10(5) A /cm(2). (C) 1998 American Institute of Physics. [S0003-6951(98)02314-6 ].