Interpretation of the critical current in Bi₂Sr₂Ca₂Cu₃O_x tape conductors as parallel weak-link and strong-link paths

To better understand the dominant mechanisms that limit the critical current density in high temperature superconductors, the dependence of the critical current density on magnetic field and temperature of Bi₂Sr₂Ca₂Cu₃O_x tapes is measured in magnetic fields up to 8 T and temperatures between 4.2 and 100 K. The results were modeled by describing the current in the tape as two parallel current paths. The critical current density of one path is limited by weak links and that of the other path by intragranular flux pinning. The temperature dependence of the parameters used in the model indicates that the weak link contribution vanishes at a temperature of 86 K. This is an indication that the weak link behavior is dominated by a remnant Bi₂Sr₂CaCu₂O_x phase. At higher temperatures the critical current density of the tape is limited by intragranular pinning.