Measurement of the q-dependent static spin susceptibility χ’(q) in YBa2Cu3O6.9

We report the temperature dependence of the q-dependent static electron spin susceptibility χ’(q) in a high-Tc superconductor YBa2Cu3O6.9 obtained by measuring the Gaussian component of Cu63 nuclear spin-spin relaxation rate 1/T2G. We employ the low-field NMR technique, and explain why this difficult technique is necessary for obtaining reliable results. It was found that χ’(q) satisfies a Curie-Weiss law at the corner of the Brillouin zone …