NMR Studies of the 60K Phase of YBC sub 0

We have investigated a series of oxygen deficient samples in the superconducting range (0.5 x = 1.0) using sup 63 Cu NQR and spin-lattice relaxation measurements. Unlike the fully-oxygenated material (x = 1.0) which presents only a single, sharp NQR line for the planar Cu(2) sites, the spectrum in oxygen deficient material contains a broad complex of planar lines at discrete frequencies. These lines are likely to reflect the various possible arrangements of oxygen vacancies on the neighboring Cu(1) chain layer.