Spin correlations and NMR relaxation rates in strongly correlated electron systems

We consider the magnetic properties of a strongly correlated electron system within the slave-boson approach. A finite concentration of holes destroys the long-range antiferromagnetic order but leaves short-range magnetic correlations intact. These correlations renormalize the interaction vertex between nuclear spin and the spin-carrying quasiparticle; the spin response functions thereby acquire a temperature dependence which is qualitatively similar to that observed in both NMR measurements and neutron-scattering data in high-temperature superconductors. The temperature dependence of 1/T1T is very prominent on the copper site, the NMR relaxation rate on the oxygen site obeys the Korringa law, whereas the spin correlations measured by neutron scattering show little temperature dependence