  We construct a class of topological excitations of a mean field in a
two-dimensional spin system represented by a quantum Heisenberg model with high
powers of exchange interaction. The quantum model is associated with a
classical one (the continuous classical analogue) that is based on a
Landau-Lifshitz like equation, and describes large-scale fluctuations of the
mean field. On the other hand, the classical model is a Hamiltonian system on a
coadjoint orbit of the unitary group SU($2s {+} 1$) in the case of spin $s$. We
have found a class of mean field configurations that can be interpreted as
topological excitations, because they have fixed topological charges. Such
excitations change their shapes and grow preserving an energy.
