FIELD-INDUCED BROADENING OF THE RESISTIVE TRANSITION AND 2-DIMENSIONAL NATURE OF FLUX PINNING IN Y2BA4CU8O16 FILMS

We report a unique dual nature of the magnetic-field-dependent resistive losses in epitaxial films of superconducting Y2Ba4Cu8O16. For excitation currents coplanar with the magnetic field, the losses are identical in the Ohmic regime for both longitudinal and transverse field orientations. In the nonlinear current-voltage regime, the transverse field results in the Lorentz-force-induced instability in the fluxline lattice and a higher dissipation. Comparison of the flux-pinning potential in Y2Ba4Cu8O16 deduced from the thermally activated nonlinear voltage with data on YBa2Cu3O7 suggests an important role of the increased separation between Cu-O superconducting planes in Y2Ba4Cu8O16 in flux pinning. © 1990 The American Physical Society.