Cu-NQR study for the disappearance of superconductivity in R1-xPrxBa2Cu3O7(R=Y and Nd)

In order to study the disappearance of superconductivity in PrBa2Cu3O7, the charged state around Cu(2) site was investigated by Cu-NQR. in the normal coxnducting and paramagnetic state in R1-xPrxBa2Cu3O7 (R=Y and Nd) over the whole range of x. The NQR. frequency of the Cu(2) site iis almost independ ent of x irrespective of R.. These results suggest that the doped holes in x=0 become localized with increasing x without substantial change of charge distribution around the Cu(2) site. The origin for the disappearance of su perconductivity in PrBa2Cu3O7 is supposed to be some mechanism without noti ceable charge transfer.