YTTRIUM AND LEAD NUCLEAR-MAGNETIC-RESONANCE INVESTIGATION OF A 1212-SUPERCONDUCTOR, PB(1+X 2)CU(1-X/2)SR2Y1-XCAXCU2O7+DELTA/

We present NMR experiments on the normal state of the 1212 superconduc tor Pb(1+x/2)Cu(1-x/2)Sr2Y1-xCaxCu2O7+delta: the samples have x-values ranging from 0.2 to 0.5, and most samples have delta-values of zero b ut there is one sample with a delta-value of 0.1. The bulk magnetic su sceptibility for all of the samples presents a temperature variation w hich can be fitted by the sum of a Curie-Weiss and a Pauli, temperatur e-independent, term. The Y-89 shift and relaxation data are compared t o those from the thallium 1212 superconductor, and to those from YBCO, showing a correlation between the shifts and the distances between th e yttrium nuclei and the copper oxide planes. We find an unusual dimer ization of the yttrium nuclei, strongly temperature dependent, reveale d by Meiboom-Gill spin-echo measurements. The Pb-207 resonance at room temperature exhibits a significant shift as the x-value (the calcium concentration) is varied, possibly indicating a monotonic variation of the Pb valence.