Superconductivity suppression of R(Ba1-zRz)(2)Cu3O7+delta (R = Nd, Pr) probed by soft-x-ray absorption spectroscopy

O K-edge x-ray-absorption near-edge-structure (XANES) spectra of (Nd1 - xPr x) 1.05Ba1.95Cu3O7 for x = 0 - 0.5 and Nd-1.05(Ba1 - zPrz) 1.95Cu3O7 + delt a for z = 0 - 0.25 were performed to search for microstructural features an d hole distribution related to the superconducting properties, Near the O 1 s edge, prepeaks at similar to 527.6 and similar to 528.3 eV are assigned t o transitions into O 2p holes located in the CuO3 ribbons and CuO2 planes, respectively. As deduced from O 1s absorption spectra of (Nd1 - xPrx) 1.05B a1.95Cu3O7 for x = 0 - 0.5, the hole concentrations in the CuO2 plants and CuO3 ribbons decrease monotonically with increasing Pr doping. The present XANES results clearly reveal that the suppression of superconductivity with Pr doping in (Nd1 - xPrx) 1.05Ba1.95Cu3O7 results predominantly from the h ole depletion effect. The effect of Pr on the Ba site in Nd-1.05(Ba1 - zPrz ) 1.95Cu3O7 + delta is to reduce the hole concentration in the CuO2 planes and to create localized fivefold Cu chain sites. T-c of Nd-1.05(Ba1 - zPrz) 1.95Cu3O7 + delta 1s depressed upon Pr doping, primarily due to hole filli ng and hole localization. Compared to (Nd1 - xPrx) 1.05Ba1.95Cu3O7, the enh anced suppression of T-c in Nd-1.05(Ba1 - zPrz) (1.95)Ci(3)O(7 + delta) is primarily due to the hole localization. [S0163-1829(99)03505-1].