Origin of size effect on superconductivity in (R-0.8 Pr-0.2)Ba2Cu3O7 studied by soft X-ray absorption spectroscopy

O K-edge X-ray absorption near-edge structure (XANES) spectroscopy of (R-0. 8 Pr-0.2)Ba2Cu3O7 (R = Y, Tm, Dy, Gd, Eu and Sm) has been performed to inve stigate the dependence of hole distribution on ionic size of the R3+ ions. Near the O Is absorption edge, pre-peaks at similar to 527.8 and similar to 528.5 eV are assigned to transitions into O 2p hole states located in the CuO3 ribbons and CuO2 planes, respectively. As deduced from O K-edge X-ray absorption spectra, the hole concentrations in the CuO2 planes decrease mon otonically with increasing ionic size of the rare-earth elements. The prese nt XANES results clearly demonstrate that the suppression of superconductiv ity in (R1-x Pr-x)Ba2Cu3O7 With ionic radius of the R3+ ions results predom inantly from the hole-depletion effect. (C) 2001 Elsevier Science B.V. All rights reserved.