Alternating current losses in biaxially textured YBa2Cu3O7-delta films deposited on Ni tapes

YBa2Cu3O7-delta films grown on rolling-assisted biaxially textured substrates carry critical current densities 10(5)-10(6) A/cm(2) at 77 K and low applied magnetic fields. In the low-field and low-current regime, ac transport current studies show hysteresis energy loss (per cycle and per unit length) roughly the value expected for a superconductor of elliptic cross section. The critical current I-c was deduced from observed de and dynamic current-voltage relations. The power loss rises sharply as I-0 (the maximum current in each cycle) is raised above I-c. In the present configuration, ferromagnetic hysteresis of the Ni substrate contributes little or no loss. (C) 1997 American Institute of Physics.