Anisotropy in the electrical resistivity and upper critical magnetic field of single-crystal Pb₂Sr₂Ho_0.5Ca_0.5Cu₃O₈

The anisotropy in the electrical resistivity ρ{variant} and the anisotropy in the upper critical magnetic field H_c2 have been investigated for Pb₂Sr₂Ho_0.5Ca_0.5Cu₃O₈ single crystals. The anisotropy in the resistivity, ρ{variant}_c ρ{variant}_ab, is 29 at 3 00K and 140 at 100K. The anisotropy in H_c2 has been determined from the angular dependence of ρ{variant} _ab(H, θ) under various constant magnetic fields. The angular dependence of H_c2 is well explained by the effective mass model. The value of γ ≡ H_c2^|/H_c2^⊥ is estimated as 12, which is larger than the 4-5 in YBa₂Cu₃O₇ and much smaller than the 19-200 in Bi₂Sr₂CaCu₂O₈. Consequently, it has been concluded that the anisotropy does not always depend on the thickness of the blocking layer but on the overlap of the electronic wave functions along the c-axis.