Upper critical field and normal-state properties of single-phase Y1-xPrxBa2Cu3O7-δ compounds

Substitution of Pr for Y in the Y1-xPrxBa2Cu3O7-δ system depresses Tc, with superconductivity disappearing for x≥0.5. The origin of this Tc depression is still controversial, as is the valence state of the Pr ion. In order to study these problems, single-phase materials were prepared with x=0.0, 0.1, 0.2, 0.3, 0.35, 0.4 0.45, 0.5, 0.6, 0.7, 0.9, and 1.0. Under certain annealing conditions, these types of samples will phase separate into YBa2Cu3O7-δ and Y1-xPrxBa2Cu3O7-δ, showing two transitions in the magnetization, but will still appear single phase from x-ray diffraction. We have overcome this problem through specific annealing conditions of time, temperature, and atmosphere. We find that the superconductivity is strongly suppressed as a function of Pr concentration, with a behavior which is consistent with the classical Abrikosov-Gor'kov pair-breaking theory. The critical fields versus T show a ''bell''-shaped behavior, which is consistent with the presence of magnetic pair-breaking interactions. The measured temperature dependence of the critical field, Hc2 near Tc, and the Pauli susceptibility, are used to estimate the physical parameters λGL, ξGL, and γ