FLUCTUATIONAL DISSIPATION IN YBA2CU3O7-DELTA IN TILTED MAGNETIC-FIELDS

We recently showed through angular measurements that in a wide range o f temperature across T-c the resistivity of twinned films of YBa2Cu3O7 -delta can be consistently described in terms of fluctuational conduct ivity. Comparison with data taken on untwinned samples reveals that th e upper part of the transition is identical for films and single cryst als, and that the same theory works well in both cases. In addition, p ure nus How may describe the data in an appreciable region of H and T in the crystal only. Wt conclude that in a wide portion of the H-T pla ne the dissipation is due solely to intrinsic properties (order-parame ter fluctuations with a possible Aux-How contribution in the crystal), while only at lower temperatures does the pinning become relevant, as supported by the breakdown of the angular scaling.