Pinning characteristics at high fields in superconducting (Bi,Pb)-2223 single crystals

Pinning properties such as the critical current density and the irreversibility field of superconducting (Bi,Pb)-2223 single crystals with different O₂ annealing conditions were investigated before and after a heavy ion irradiation which nucleated columnar defects parallel to the c-axis. The critical current density was enhanced by a factor of 3 to 4 after the irradiation due to the strong pinning effect by the columnar defects. In addition, the irreversibility field was also improved, and the improvement becomes larger at higher temperatures. The enhancement of the pinning properties was larger in O₂ annealed specimen, suggesting an improvement of the dimensionality of the superconductivity. The experimental results were theoretically analyzed using the flux creep-flow model. It was found that the theoretical prediction can explain the experimental results of the critical current density and the irreversibility field.