HALL-ARRAY MEASUREMENTS OF FLUX-CREEP PARAMETERS IN Y-BA-CU-O CRYSTALS

We describe the details of a new method for studying thermally activat ed flux creep in superconductors. This method employs an array of micr oscopic Hall sensors to probe the time evolution of the field profile in the sample. We analyze these data on the basis of a continuity equa tion which takes into account contributions to the relaxation process from both the in-plane and out-of-plane components of the induction fi eld. This analysis enables direct determination of flux creep paramete rs such as the flux-line current density, flux-line velocity and the a ctivation energy for flux creep. We demonstrate this method by present ing experimental data far YBa2Cu3O7-x crystals in the remanent state a nd in the presence of a field.