Spinless Impurities in High- $T_c$ Cuprates: Kondo-Like Behavior

We compare the effects of in-plane nonmagnetic ${\mathrm{Li}}^{+}$ and ${\mathrm{Zn}}^{2+}$ impurities on the normal state of high- $T_c$ cuprates. ${}^{89}\mathrm{Y}$ NMR shows that the extra hole introduced by Li is not localized in its vicinity. The $T_c$ depression and induced moments on near neighbor Cu sites of Zn or Li are found to be identical. These effects of spinless impurities establish the major influence of the spin perturbation with respect to the charge defect. The susceptibility of the induced moment measured by ${}^7\mathrm{Li}$ NMR displays a $1/(T+\Theta )$ behavior. $\Theta$ increases with doping up to about 200 K in the overdoped regime. We attribute this to a “Kondo-like” effect.