Flux Creep and Temperature Dependence of the Transport Critical Current Density in High-Tc Superconductors

Abstract

We report measurements of the transport critical current density Jc of thin films and bulk ceramic specimens of high-Tc superconductors as a function of temperature in the range 4.2 K to Tc under self-field conditions. Theoretical models for thermally activated flux creep in homogeneous superconductors, and for current transport across Josephson weak links (S-I-S and S-N-S junctions) are used to analyze the temperature dependence of Jc. We find that flux creep determines the temperature dependence of the critical current density Jc(T) of specimens, and that Jc(T) increases approximately linearly with decreasing temperature for t ≤ 0.7 (where t = T/Tc). Fits to the data are obtained using a barrier potential U(0) = 10kTc = 65–90 meV.