On the pressure dependence of Tc of the Y1-xPrxBa2Cu3O7-δ system

It is shown that the crossover which occurs with increasing x near x≅0.2 in the pressure dependence of the superconducting critical temperature Tc from positive to large negative values for the Y1-xPrxBa2Cu3O7-δ (δ≅0.05) system can be accounted for using a simple phenomenological model, generalized to include pressure. The model was developed to describe the dependence of Tc on the concentrations of Pr (x) and Ca (y) in the Y1-x-yPrxCayBa2Cu3O7-δ system and incorporates (1) the counteracting effects of the generation and annihilation of holes in the conducting CuO2 planes by Ca2+ and Prn+ ions (where +n is the Pr valence), respectively, and (2) the depairing of superconducting electrons via exchange scattering of the mobile holes in the CuO2 planes by the Pr magnetic moments. New measurements of Tc(P) on higher quality Y1-xPrxBa2Cu3O7-δ specimens are presented and analyzed in terms of the phenomenological model. The increase in the magnitude of the normal state electrical resistivity with pressure observed in an Y0.5Pr0.5Ba2Cu3O7-δ specimen is consistent with the decrease in the mobile hole concentration with pressure inferred from the model. (orig.)