Influence of the Flux Creep on the Critical Current Density in Bi₂Sr₂Ca₂Cu₃O_x and Y(Ho)Ba₂Cu₃O_y Superconductors

Abstract

Intragrain J c values of the textured Bi- and Y-based oxides were obtained at 4.2 K–77 K by the D.C. magnetization measurements with various sweep rates of the magnetic field. The J c 's at 4.2 K were comparable for both oxides. However, with increasing temperature, the J c of the Bi-based oxide became much more sensitive to the electric field criterion E c related to the sweep rate of the magnetic field than that of the Y-based oxide. As a result, J c at 77 K of the Bi-based oxide was significantly decreased in magnetic fields for small E c . The dependence of J c on E c for both oxides can be well understood using the flux creep model.