High field critical current density and flux ''melting'' in C-oriented high-Tc phase BiPbCaSrCuO thin film

Current-voltage (I-V) curves were measured on a high-Tc phase BiPbCaSrCuO thin film with Tc=109.8 K. The I-V characteristics follow a power law which can be described by the flux creep model. The Jc(H) under the perpendicular field (Hparallelc-axis) decreased exponentially with the increase of magnetic field below 34.9 K, and decreased to zero at low fields due to the thermally assisted flux flow above 34.9 K. We ascribe this behaviour to the misalignment of CuO2 planes which result in defect sheets acting as superconductor/normal-material/superconductor (SNS) weak links at sufficiently large fields. The Jc(H) under the parallel field (Hperpendicular toc-axis) resembles a dissipation mechanism similar to the conventional type II superconductors and to YBa2Cu3O7 thin films. The possibility of flux melting is discussed considering the micro-structure of the sample. (orig.)