E-J characteristic and flux pinning in superconducting PbBi alloys

The characteristics of electric field E vs. current density J at various magnetic fields and temperatures in superconducting PbBi samples with different pinning strength were measured by using a usual resistive method. The obtained E-J curves show a nonlinear behavior similar to that in high T/sub c/ superconductors (HTSC). With a scaling generally used in HTSC, E-J curves collapse onto one of the two universal branches, with the exponents of /spl nu/ and z similar to those reported in HTSC. It was found that the stronger flux pinning strength leads to the higher transition points of T/sub g/ and B/sub g/ in the E-J characteristic. The nonlinear E-J curves and the enhancement of the transition points were explained and reproduced by using the flux creep and flux flow theory.