NON-LINEAR EXCITATIONS IN CLASSICAL FERROMAGNETIC CHAINS

General single solitary-wave excitations are determined for the classical continuum Heisenberg chain in the presence of external magnetic and anisotropy fields. These include both domain walls and pure solitons as examples. Conditions for propagation are carefully analysed. The complete integrability of the zero-anisotropy limit is suggested as a basis for (i) controlled singular perturbation theory, and (ii) formulation of classical statistical mechanics in a natural configurational (nonlinear normal mode) representation.