Anisotropic magnetic penetration depth of grain-aligned HgBa2Ca2Cu3O8+ delta.

The temperature (T) dependence of the anisotropic magnetic penetration depth Λ(T) of magnetically aligned powders of crystalline HgBa2Ca2Cu3O8+δ is reported. Measurements were performed in the Meissner state using the ac-susceptibility technique. The temperature dependences of the in-plane, Λab(T), and out-of-plane, Λc(T), penetration depths are markedly different. This is believed to arise from the large anisotropy ratio γ=[Λc(0)/Λab(0)]≃30. The behavior of Λab(T) is indicative of d-wave superconductivity while Λc(T) is similar to the behavior expected for a superconductor with intrinsic Josephson coupling between the CuO2 planes. Similar measurements were performed on Ba0.6K0.4BiO3 powders for comparison