Field dependence of current profiles induced in a superconducting film under a magnetic field

Abstract

The field dependence of current profiles induced in a superconducting SmBa2Cu3O7 (SmBCO) film grown on an ion beam assisted deposition (IBAD) template in the coevaporation method was investigated. The field profiles near the surface of the film under external fields were measured using a scanning Hall probe method. The magnetic field was normal to the film surface and was increased monotonically from 0 to 1800 Oe in 90 Oe step. The corresponding current profiles in the superconducting thin film were obtained by using a numerically iterative inversion of the measured field profile data. We found that the sheet current density profile was very different from the theoretically calculated one based on the Bean model. When the applied field, H-a, was increased up to 270 Oe, the maximum values of the current profiles reached the highest value, which was similar to its critical current density at H-a = 270 Oe and which decreased for further increases of H-a. We investigated the field profiles, H-super(x), produced only by the superconducting current. The values of H-super(x) saturated under the conditions of H-a = 270 Oe. We think that these features may be due to a mixture of the shield current and the critical current induced in the granular structure of the sample. After the Meissner region disappeared at higher fields, the values of J(x) showed the field dependence feature of the critical current.