Spinless impurities in high Tc cuprates: Kondo-like behavior

Abstract

We compare the effects of in-plane non magnetic Li$^{+}$ and Zn$^{2+}$ impurities on the normal state of high-T$_{c}$ cuprates. Y NMR shows that the extra hole introduced by Li is not localized in its vicinity. The Tc depression and induced moments on near neighbour Cu sites of Zn or Li are found identical. These universal 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 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.