Local spin polarization in underdoped cuprates with impurities

We present a theory of magnetic (Ni) and nonmagnetic (Zn) impurities substi tuted into planar Cu sites in the normal state of underdoped cuprates exhib iting a spin gap. Both types of impurities induce magnetic moments on neigh boring Cu sites. In the case of Ni, these moments partially screen the inhe rent impurity spin, resulting in an effective S = 1/2 moment. The character istic Kondo scale is found to have a power-law dependence on the coupling c onstant. We investigate the spatial shape of the impurity-induced spin dens ity, taking into account the presence of short-ranged AF correlations, and calculate the O-17 NMR line broadening induced by impurity doping. (C) 1999 Elsevier Science B.V, All rights reserved.