  So far calculations of the spin susceptibility in the superconducting state
of cuprates have been performed in the framework of weak-coupling
approximations. However, it is known that cuprates belong to Mott-Hubbard doped
materials where electron correlations are important. In this paper an
analytical expression for the spin susceptibility in the superconducting state
of cuprates is derived within the singlet-correlated band model, which takes
into account strong correlations. The expression of the spin susceptibility is
evaluated using values for the hopping parameters adapted to measurements of
the Fermi surface of the materials YBa2Cu3O7 and Bi2Sr2CaCu2O8. We show that
the available experimental data which are directly related to the spin
susceptibility can be explained consistently within one set of model parameters
for each material. These experiments include the magnetic resonance peak
observed by inelastic neutron scattering and the temperature dependence of the
NMR spin shift, spin-spin and spin-lattice relaxation rates in the
superconducting state.
