Effect of Be and Zn doping in Bi2Pb0.6Sr2Ca2Cu3Oδ superconductors using ac susceptibility measurements

Ac complex susceptibility, chi = chi' - i chi ", measurements were done on the samples doped with barium and zinc (Bi2Pb0.6Sr2Ca2 - xMxCu3Odelta, M = Ba, Zn and x = 0.02 and 0.10). The data of chi' shows that coupling of the grains in Zn-doped samples are weaker than that of Ba-doped samples and hence it could be concluded that Zn-doped samples are dominated by the S-I-S type of weak links, whereas the Ba doped samples are dominated by the S-N-S weak links. Calculated values of l(0) is three times higher in the Ba doped samples such that the values of Josephson coupling energy, E-j is four times that of Zn doped samples. Analysis based on the sensitivity of the data of d chi'(T)/dT versus temperature furnished further information on the two-step transitions related to the coupling of the grains in both systems. (C) 1999 Kluwer Academic Publishers.