CU NMR AND NQR STUDIES OF IMPURITIES-DOPED YBA2(CU1-XMX)3O7 (M = ZN AND NI)

The normal and superconducting properties in impurity-doped YBa2(Cu1-x Mx)3 O7 (M=Zn and Ni) have been investigated by Cu-63 NMR and NQR tech niques. The nonmagnetic Zn-doping into the CuO2 plane in YBa2Cu3O7(YBC O7) causes a local collapse of antiferromagnetic (AF) spin correlation near Zn impurities and induces a gapless superconductivity with a fin ite density of states at the Fermi surface. On the other hand, in the case of Ni doping, there is no appreciable modification except for a s mall decrease of T(c), although the Ni spins behave actually as local moments. The gapless feature iri Zn-doped YBCO7 is shown to be consist ently interpreted within the framework of the d-wave model with gap ze ros of lines at the Fermi surface as argued in heavy fermion supercond uctors. It is pointed out that the AF spin fluctuation-induced superco nductivity is applicable to high-T(c) cuprates.