Temperature and magnetic field dependence of the critical current of Bi2Sr2Ca2Cu3Ox tape conductors

In order to improve the understanding of the dominant mechanisms that limit the critical current in high temperature superconductors, the dependence of the critical current on magnetic field and temperature of a Bi₂Sr₂Ca₂Cu₃O_x tape has been investigated in detail. The critical current is measured in magnetic fields up to 8 T, at temperatures ranging from 4.2 K to 70 K. The results are compared with existing models that describe the current path as two parallel systems, one depending on weak links and the other on flux pinning. The critical current at low magnetic fields is reduced drastically by the self-field of the superconductor. At intermediate magnetic fields, the field dependence of the critical current is mainly dominated by weak links, while at higher fields it is dominated by the strong-links current path, and depends on flux pinning. To clarify the models used to describe the measurements, the temperature dependence of the parameters used in the models is studied. The temperature dependence of the parameters used to describe the weak-links current path points out that the weak links are formed by remnant Bi₂Sr₂Ca₁Cu₂O_x phase at the grain boundaries