Hall-array measurements of flux creep parameters in Y-Ba-Cu-O crystals

We describe the details of a new method for studying thermally activated flux creep in superconductors. This method employs an array of microscopic Hall sensors to probe the time evolution of the field profile in the sample. We analyze these data on the basis of a continuity equation which takes into account contributions to the relaxation process from both the in-plane and out-of-plane components of the induction field. This analysis enables direct determination of flux creep parameters such as the flux-line current density, flux-line velocity and the activation energy for flux creep. We demonstrate this method by presenting experimental data for YBa₂Cu₃O_7-x crystals in the remanent state and in the presence of a field.