Anisotropy of superconducting Pb2Sr2(Y0.7Ca0.3)Cu3O8+δ and Pb2Sr2Y1-yCu3O8+δ

The London-penetration-depth anisotropy ratio γ of Pb2Sr2(Y0.7Ca0.3)Cu3O8+δ and Ca-free Pb2Sr2Y1-yCu3O8+δ (y≊0.1) single crystals has been measured by the equilibrium torque magnetometry method. γ values are found to be in the range of 10 to 11 and are comparable to that of YBa2Cu3O7-δ rather than Bi2+xSr2Ca1-xCu2O8+δ although Pb2Sr2(Y0.7Ca0.3)Cu3O8+δ is structurally similar to both, with its c-axis lattice constant 30% larger than that of YBa2Cu3O7-δ. The γ of a Pb2Sr2(Sm0.5Eu0.5)Cu3O8+δ crystal was measured to be 13±3.