Theory of impurity-induced NMR line broadening in underdoped cuprates

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, which in the case of Ni partially screen the inherent impu rity spin, resulting in an effective S = 1/2 moment. We investigate the imp urity-induced polarizability, taking into account the presence of short-ran ge AF correlations, and calculate the O-17 NMR line broadening induced by i mpurity doping. (C) 1999 Elsevier Science B.V. All rights reserved.