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/${\mathit{T}}_1$T 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.