On the anomalous oxygen-number dependence of the superconducting transition temperature of R1-xPrxBa2Cu3O6+y (R=Y and Sm)

Superconducting transition temperatures T-c and their pressure dependence of Y1-xPrxBa2Cu3O6+y and Sm1-xPrxBa2Cu3O6+y have been studied. Transport studies and NQR/NMR measurements on Y1-xPrxBa2Cu3O6+y have also been carried out for various values of x and y. Anomalous dip-structure has been confirmed to appear, with increasing Pr concentration x, in the T-c - y curves drawn for fixed x values in both systems. However, in the Hall coefficients and the thermoelectric powers of the Pr-doped systems, we have not found any anomalous behavior which indicates the existence of the "stripe ordered" phase even for tilt? samples located within the dip region of the T-c - y curve, exhibiting a clear contrast with the cases of La2-xBaxCuO4 and La2-x-yNdySrxCuO4. Instead, it is shown that the dip-structure can basically he explained as the result of both the reduction of the conducting holes due to the hole-trapping by the Pr4f-O2p(pi) hybridized orbits and the pair breaking by the trapped holes.