Complex Susceptibilities of Pr-doped Y₂Ba₄Cu₇O_15-d Synthesized by the Polymerized Complex Method

We studied the magnetic response of Pr-doped Y₂Ba₄Cu₇O_15-d oxide superconductors, Y_2-xPr_xBa₄Cu₇O_15-d (x=0.0-1.2) in terms of complex susceptibility x=x′-ix″. The samples were synthesized by the polymerized complex method. For all the samples, the superconducting transition was observed. As expected, the onset temperature decreased with increasing x. By means of X-ray analysis, we determined the lattice constants, of which the Prcontent dependence showed a slight increase with increasing x. However, the variation is much smaller than those for the case of the 123 and 124 phase, suggesting that the charge state of Pr in the 247 phase can take either +3 or +4 state.