CU AND O NMR-STUDIES OF THE MAGNETIC-PROPERTIES OF YBA2CU3O6.63(TC=62K)

The microscopic magnetic properties of the CuO2 planes in YBa2Cu3O6.63 (T(c) = 62 K) have been investigated in Cu and O NMR experiments. Unlike the fully oxygenated Y-Ba-Cu-O7 (T(c) congruent-to 90 K), the various components of the Cu and O Knight-shift tensors show strong but identical temperature dependences in the normal state. This supports the picture that there is only one spin component in the CuO2 planes. The spin susceptibility deduced from Knight-shift results shows significant reduction with decreasing temperature in the normal state. The temperature dependences of the nuclear-spin-relaxation rates (1/T1) are very different for the Cu and the O sites. 1/(T1T) at the O sites is nearly proportional to the spin susceptibility. 1/(T1T) at the Cu sites shows a broad peak around 150 K. We discuss these relaxation behaviors based on a model of the dynamical spin susceptibility proposed by Millis, Monien, and Pines.