Excitation Spectra of Plane Site Cu Spins of Y_0.52Pr_0.48Ba₂Cu₃O₇ (Tc≃20 K)

Neutron inelastic scattering measurements have been carried out on Y_0.52Pr_0.48Ba₂Cu₃O₇ with the superconducting transition temperature Tc≃20K. From the spectral weight function χ(q, ω) of the Cu-spin excitations in the CuO2 planes, the reduction of the hole-carrier concentration and the degree of the randomness induced by the substitution of Pr for Y are estimated. These results present evidences that the model of a hole-trapping by the hybridized states of the Pr4f and O2pπ orbitals proposed by Fehrenbacher and Rice [Phys. Rev. Lett. 70 (1993) 3471] provides an appropriate explanation of the experimental results associated with the well-known Tc suppression of R1-xPrxBa2Cu3O7 (R = Y or various lanthanide elements) by the Pr-doping.