  A strong nonmagnetic impurity can induce a resonance state in the d-wave
superconducting state. As far as magnetic properties are concerned, this
resonance state behaves effectively like a free moment. It leads to a
Curie-Weiss-like magnetic susceptibility in an intermediate temperature regime
below $T_{c}$. From the impurity susceptibility, the effective moment of the
resonance state is deduced and compared with experiments. The contribution of
the resonance to the magnetic susceptibility can account for the main feature
of the NMR spectra in overdoped high-$T_c$ materials. In the underdoped regime,
the contribution from the resonance to the magnetic susceptibility is also
substantial, but the effective moment of the resonance is smaller than the
total moment induced by a nonmagnetic impurity.
