NMR IN HIGH-TC OXIDE SUPERCONDUCTORS

Cu-63 NQR and NMR studies are extensively reported in La2-xSrxCuO4 (LSCO), heavily-doped Tl2Ba2CuO6+y (TBCO) and Zn-doped YBa2Cu3O7 (YBCO7). The nuclear spin-lattice relaxation (T1) study extracts that the antiferromagnetic (AF) spin correlation becomes less distinct with decreasing T(c) in heavily-doped TBCO over an optimum hole content. In non-superconducting TBCO, the AF spin correlation disappears, suggesting an intimate interrelation between the occurrence of the superconductivity and the presence of the AF spin correlation. In superconducting state, both the T1 and Knight shift results in undoped- and Zn-doped YBCO7 are consistently understood within a simple model combining both effects of the gap zeros of lines at the Fermi surface arising from d-wave pairing and of the small but finite residual density of states at the Fermi level induced by some impurity and some imperfection.