MAGNETIC CORRELATIONS AND SPIN DYNAMICS IN THE T-T'-J MODEL

Using a generalized RPA expression for the spin susceptibility, we inv estigate the spin dynamical properties in the normal state of the meta llic cuprates on the basis of a spin-rotation-invariant slave boson re presentation of the t-t'-J model, where the second-neighbour hopping t ' incorporates important correlation and band structure effects near h alf-filling. We attribute the contrasting q dependence of the magnetic structure factor S(q, omega) seen in neutron scattering experiments f or LSCO- and YBCO-type systems to differences in their Fermiology. Ass uming that the antiferromagnetic correlations are spatially filtered b y the hyperfine form factors, we calculate the temperature dependences of spin-lattice and spin-spin relaxation rates for planar copper and oxygen sites: the results agree qualitatively well with various experi ments on YBa2Cu3O6+x.