SUPPRESSION OF SUPERCONDUCTIVITY IN PRBA2CU3O7 - 4-F AND CONDUCTION-BAND HYBRIDIZATION EFFECT

In order to understand the suppression of superconductivity in Y1-xPrxBa2Cu3O7 (0.6x1.0) and also the electronic properties of the high-Tc superconductors RBa2Cu3O7 (R denoting the rare earths except Ce, Pr, Pm, and Tb), we have performed self-consistent, spin-polarized electronic structure and all-electron total-energy calculations for three representative materials: RBa2Cu3O7 (R=Y, Pr, and Gd). The salient results are that the band structures of the RBa2Cu3O7 compounds are nearly the same as that of YBa2Cu3O7 when R ions assume trivalency, and extra electrons donated by the hypothetical tetravalent Pr ions would mainly fill the conduction bands in a rigid-band manner, thereby substantially reducing the important hole account. However, the tetravalent Pr compound is shown to be energetically less favorable than the trivalent Pr compound; finally, large spin splittings (up to 75 meV) are found in the conduction bands around the Fermi level in PrBa2Cu3O7 when the 4f and conduction-band hybridization effects are taken into account. In contrast, such spin splittings are ten to five times smaller in GdBa2Cu3O7. This result corroborates that the magnetic pair breaking is responsible for the suppression of superconductivity in the Pr compound. © 1990 The American Physical Society.