Fluctuational dissipation in YBa2Cu3O7-δ in tilted magnetic fields

We recently showed through angular measurements that in a wide range of temperature across Tc the resistivity of twinned films of YBa2Cu3O7-δ can be consistently described in terms of fluctuational conductivity. Comparison with data taken on untwinned samples reveals that the upper part of the transition is identical for films and single crystals, and that the same theory works well in both cases. In addition, pure flux flow may describe the data in an appreciable region of H and T in the crystal only. We conclude that in a wide portion of the H-T plane the dissipation is due solely to intrinsic properties (order-parameter fluctuations with a possible flux-flow contribution in the crystal), while only at lower temperatures does the pinning become relevant, as supported by the breakdown of the angular scaling. copyright 1997 The American Physical Society