Lower critical field and reversible magnetization of (Bi, Pb) 2Sr 2Ca 2Cu 3O x superconducting whiskers

Abstract

Magnetization measurements have been carried out on Pb doped Bi 2Sr 2Ca 2Cu 3O x (Bi-2223) whiskers with the applied field parallel to the c-axis. The temperature dependence of the first flux penetration field H p can be approximated by H p( T) = H p(0)[1 − ( T/ T c) 2] in the region T > 50 K, while it increases upward with decreasing temperature especially at T < 30 K due to the surface barrier. The value H p = H c1(0) = 135 G is obtained by fitting the experimental data for T > 50 K. The penetration depth has depth also been evaluated from the reversible magnetization curves. λ ab − is a linear function of the H c(0) = 3300 G have been calculated from the H c1(0) value together with the tupper critical field and coherence lenghts. penetration depth has also been evaluated from the reversible magnetization curves. λ ab −2 is a linear function of the temperature near T c.