To investigated the nature of the in-plane vortex dissipation of underdoped Y1-xPrxBa2Cu3O7-δ single crystals, we performed in-plane angular magnetoresistivity measurements over a wide range of temperatures and magnetic fields, below and above the zero field critical temperature, for a large range of Pr concentrations (0 ≤ x ≤ 0.53). We found that the angular dependence of in-plane magnetoresistivity shows three temperature T regimes: (a) a low T regime which extends from below to above the critical temperature Tc0 up to an x dependent temperature (e.g., up to 1.15 x Tc for x = 0.46) displaying a two dimensional 2D scaling (consistent with pancake-like excitations); (b) an intermediate T regime, corresponding to vortex line excitations, which extends up to temperature Tφ > Tc0; (c) a high T regime for T > Tφ in which the quasiparticles dominate the dissipation. The electronic phase diagram shows that Tφ(x) departs from Tc0(x) for x ≥ 0.20 and reaches a maximum at x = 0.46.
In order to investigate the origin of the large out-of-plane resistivity ρc and its temperature T, magnetic field H, and angle θ dependence in underdoped Y0.54Pr0.46Ba2Cu3O7-δ single crystals, we analyzed the out-of-plane dissipation in these materials at temperatures close to the critical temperature Tc0. For this goal, we carried out T and θ dependent ρc measurements both below and above the critical temperature. We found that the Ambegaokar-Halperin relationship for Josephson junction [V. Ambegaokar, and B. I. Halperin, Phys. Rev.Lett. 22, 1364 (1969)] depicts very well the angular magnetoresistivity in the investigated range of magnetic field and temperature. The main finding of this investigation is that the in-plane phase fluctuations decouple the layers above the critical temperature where the charge transport is governed only by the quasiparticles. We also calculated the interlayer Josephson critical current density, which was found to be much smaller than the one predicted by the theory of layered superconductors. This discrepancy could be a result of the d-wave symmetry of the order parameter and/or of the non Bardeen-Cooper-Schriffer (BCS) temperature dependence of the out-of-plane penetration length.