LFMA AND IRREVERSIBILITY LINE STUDIES ON VANADIUM-DOPED BI(2223) SUPERCONDUCTING SYSTEM

Suresh Babu ct al [7] have reported the stabilization of Bi high T-c ( 105 K) phase by vanadiun oxide doped Bi(2223) superconducting system. Stabilization of Bi high T-c phase in the absence of Pb makes this sys tem interesting. In this paper we report low field microwave absorptio n (LFMA) studies of Bi2-xVx Sr-2 Ca-2 Cu-3 O-y (x=O and 0.4) supercond ucting samples. Temperature dependent LFMA signal amplitude of x=O sam ple showed definite peaks at 97 K and 70 K which may correspond to the 2223 and 2212 phases. In the case of x=0.4 sample, it showed a single peak at 90 K corresponding to 2223 phase. The thermodynamical critica l magnetic field H(c1) and average Josephson loop diameter was estima ted for these samples from the LFMA signals. In addition we have also determined the irreversibility line from ZFC and FC susceptibility mea surements. The irreversibility line followed the universal law H=H-o( 1-T/T-c)(n).n and H-o were found to be 2.8 and 4075 Oe respectively.