  Local magnetic properties around a nonmagnetic impurity are investigated in
high-Tc cuprate superconductors. We consider a model two-dimensional d-wave
superconductor with strong antiferromagnetic (AF) spin fluctuations and
calculate the spin susceptibility around the impurity. We show that the uniform
susceptibility, which is usually suppressed in spin-singlet superconductivity,
is enhanced at low temperatures around the impurity when the impurity
scattering is in the unitarity limit. This anomalous behavior is more
remarkable when the impurity potential is extended spatially and the AF spin
fluctuations are stronger. As the origin of this phenomenon, we point out the
importance of (1) a low-energy bound state around the impurity and (2) a
mode-mode coupling effect which connects the AF spin fluctuations with the
uniform susceptibility. Our results can explain the anomalous temperature
dependence of the Knight shift on Li which was recently observed in
YBa_2(Cu_{1-x}Li_x$)_3O_{6+y}.
