Quasiclassical approximation for the models of spin-spin interaction on the one-dimensional lattice

The one-dimensional anisotropic Heisenberg model in the exterior field is considered. For the corresponding energy operator with parameter $h$ the quasiclassical ($h\to0$) spectral expansion is constructed. In the integrable case (in the absence of the exteriour field) the results obtained coincide with the exact ones.