O-17 NMR comparison of zinc and nickel substituted YBa2Cu3O6.6

O-17 NMR measurements of the width of the line of the CuO2 planes were performed in underdoped YBaCuO samples with Zn and Ni substitution. Contrary to the usual observation in optimally doped compounds, the impurity induced widths are found to deviate markedly from a 1/T Curie law. An interpretation is given in terms of a temperature dependence of the static susceptibility chi'(q) of the pure compound near Q(AF).