Y-89 NMR-STUDY OF THE EFFECTS OF IMPURITIES ON AND BETWEEN THE CUO2 PLANES IN HIGH-T-C SUPERCONDUCTING CUPRATES

We have performed Y-89 NMR, susceptibility and thermoelectric power me asurements on the Y1-xCaxBa2-xLaxCu4O8 superconductor to investigate t he effects of impurities between the superconducting CuO2 planes. The results are compared with Zn and Ni impurities in YBa2Cu4O8 that subst itute primarily for Cu within each superconducting CuO2 plane. Interpl anar impurities result in negligible pair breaking while intraplanar i mpurities lead to a rapid depression in T-c. This is consistent with t wo-dimensional superconductivity within each CuO2 plane and weak inter planar coupling. The Ca, La, Zn, and Ni impurities all lead to similar increases in the Y-89 NMR linewidth at 293 K with increasing impurity concentration indicating, contrary to previous reports, that an induc ed local moment is not responsible for the linewidth increase. [S0163- 1829(98)02417-5].