Knight shifts and nuclear-spin-relaxation rates for two-dimensional models ofCuO2

Using spin-wave and random-phase-approximation expressions for the dynamic spin susceptibility of a two-dimensional ${\mathrm{CuO}}_2$ lattice, we have calculated the NMR Knight shifts K and spin-relaxation rates $T_1^{\mathrm{-}1}$ at various nuclear sites for the insulating and metallic phases. Our results suggest that the observed differences in the NMR data taken on different sites are qualitatively consistent with a model that has strongly hybridized Cu(3d)-O(2pσ) orbitals. Within this picture, local antiferromagnetic correlations produced by on-site Coulomb interactions enhance the large-momentum part of the spin susceptibility. These correlations are then spatially filtered by the hyperfine form factors leading to different local-site behavior.