NMR and NQR study of copper in Ba sub 2 YCu sub 3 O sub (delta- 7).

Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies of copper nuclei are reported for high-quality single-phase powder samples of Ba sub 2 YCu sub 3 O sub (7- delta). The high-field sup (63) CU NMR spectrum shows well- defined axial symmetry for the chain-forming Cu1 site and evidence of appreciable disorder in the Cu2 planes. Spontaneous oxygen loss was found to degrade the sharp NMR spectrum of the Cu1 site. Spin-lattice relaxation rates reveal strikingly different electron dynamics for the two sites. For neither site do the rates exhibit conventional BCS behavior near T sub c.