Using substitutions and O-17 NMR to probe the susceptibility chi '(Q) in underdoped YBa2Cu3O6+y and HgBa(2)CuO4+delta compounds

We present O-17 NMR measurements of Zn and Ni substituted bilayer YBaCuO an d Zn substituted monolayer HgBaCuO in the underdoped regime. The Zn and Ni magnetic moments induce a broadening of the CuO2 plant: O-17 NMR spectrum, which is directly linked with the intrinsic susceptibility chi'(q) of the p lanes. The temperature dependence of this broadening does not scale with th e Zn or Ni susceptibility. This deviation is similar for bilayers and monol ayers. Numerical simulations allow us to associate this deviation with the T-dependence of the amplitude of the antiferromagnetic staggering susceptib ility. Comparison with literature shows that the correlation length xi is n early T-independent. (C) 1998 Elsevier Science Ltd. All rights reserved.