Superconducting layer thickness of relaxation properties of persistent current in high magnetic field in YBCO-coated conductor

It was previously shown that the apparent pinning potential U0∗ associated with the relaxation of superconducting current at low magnetic fields depended on the thickness of superconducting layer for IBAD/PLD-processed YBCO-coated conductors. It is necessary to clarify the thickness dependence of the relaxation property at high magnetic fields for application of YBCO-coated conductors in a persistent current mode at such magnetic fields. In this study, the thickness dependence was investigated in the field range of 1-6 T at 20 K for IBAD/PLD-processed YBCO-coated conductors with the superconducting layer thicknesses of 0.25-1.0μm. It was found that U0∗ decreases monotonically with decreasing thickness at 6 T. This seems to be attributed to the two-dimensional pinning mechanism because of the longitudinal flux bundle size limited by the film thickness.