Cu-63,Cu-65 NQR study of Zn and Ni doped YBa2Cu2O3O7

Cu-63,Cu-65 NQR measurements have been performed on Zn and Ni doped. YBCO ( YBa2Cu3-xMxO7, M=Zn or Ni, x=0.0 similar to 0.09). Distinctive differences due to the nonmagnetic Zn and the magnetic Ni dopants substituted for coppe r are compared microscopically based on. the plane and the chain Cu-63,Cu-6 5 NQR data. Both spin-lattice and spin-spin relaxation rates decrease for Z n doped YBCO whereas they increase for Ni doped YBCO. From the isotopic rat io of Cu-63,Cu-65 spin-lattice relaxation rate, a dominant relaxation mecha nism is determined as a function of concentration and discussed in conjunct ion with magnetic moments of the dopants.