Muon spin relaxation in Re-substituted HgA₂Ca_n-1Cu_nO_2n+2+x (A=Sr,Ba; n=2,3) superconductors

The muon relaxation rate σ for the Re-substituted HgSr₂CaCu₂O_6+y and HgBa₂Ca₂Cu₃O_8+y superconductors has been measured as a function of temperature. The low-temperature values of σ fall close to the universal Uemura line T_c(σ), as observed for other layered superconductors; therefore our data show no evidence of a reduced anisotropy, i.e., interlayer metallization, induced by Re. The in-plane penetration depth values obtained for these 1212 and 1223 compounds are found to be significantly different (λ=1665 Å and λ=1310 Å, respectively). The roles of the inserted CuO₂ planes, the Ba/Sr substitution and the character of the spacing layers are considered to discuss the observed features.