Magnetic-flux distribution and the magnetic penetration depth in superconducting polycrystalline Bi2Sr2Ca1−xYxCu2O8+δ and Bi2−xPbxSr2CaCu2O8+δ

Abstract

Results on the systematics of the magnetic penetration depth λab in the high-temperature superconductors Bi2Sr2Ca1−zYzCu2O8+δ (z=0,0.1,0.2,0.3,0.4,0.45) and Bi2−xPbxSr2CaCu2O8+δ (x=0.15,0.30,0.70) are reported from muon-spin-rotation measurements on polycrystalline samples with known oxygen excess δ. In determining λab 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 λab in the Y-doped compounds correlates in the expected manner with the nominal hole-carrier concentration p (λab−2∝p) while the Pb-doped compounds λab 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 λab−2 and Tc in the manner seen in the 1:2:3 family is found in the present case.

Source-reported materials — not catalogue approval

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