Magnetic-Flux Distribution And The Magnetic Penetration Depth In Superconducting Polycrystalline Bi2sr2ca1-Xyxcu2o8+Delta And Bi2-Xpbxsr2cacu2o8+Delta

Results on the systematics of the magnetic penetration depth lambda(ab) in the high-temperature superconductors Bi2Sr2Ca1-zYzCu2O8+delta (z = 0, 0.1, 0.2, 0.3, 0.4, 0.45) and Bi2-xPbxSr2CaCu2O8+delta (x = 0.15, 0.30, 0.70) are reported from muon-spin-rotation measurements on polycrystalline samples with known oxygen excess delta. In determining lambda(ab) various additional sources for inhomogeneous internal field distributions, besides the one arising from the flux-line lattice, have been critically taken into account. The most important one arises from a type of powder broadening due to the anisotropy of the field-cooled magnetization. It is found that lambda(ab) in the Y-doped compounds correlates in the expected manner with the nominal hole-carrier concentration p(lambda(ab)-2 is-proportional-to p) while the Pb-doped compounds lambda(ab) is practically independent of p. It is concluded that Pb doping (valence state is + 2) does not increase the density of free charge carriers in agreement with results from Hall-effect measurements. No correlation between lambda(ab)-2 and T(c) in the manner seen in the 1:2:3 family is found in the present case.