  We report a systematic study of Zn-substitution effect on Cu NQR spectrum for
high $T_c$ superconductors La$_{2-x}$Sr$_x$Cu$_{1-y}$Zn$_y$O$_4$ from
carrier-underdoped to -overdoped regimes (polycrystalline samples, $x$ =0.10,
0.15, and 0.20). We observed no appreciable wipeout effect for the overdoped
samples, a gradual and partial wipeout effect below about 80 K for the
optimally doped ones, and very abrupt and full wipeout effect below about 40 K
for the underdoped ones. The wipeout effect indicates a highly enhanced
spectral weight of Cu spin fluctuations at a low frequency. We associate the
wipeout effect with a Zn-induced local magnetism far above 40 K and with a
localization effect below 40 K.

Superconductivity;Strongly Correlated Electrons