Soliton spin excitations in an anisotropic Heisenberg ferromagnet with octupole-dipole interaction

We investigate the nonlinear spin dynamics of an anisotropic Heisenberg fer romagnetic spin chain with octupole-dipole interaction in the semiclassical limit using the coherent-state method combined with the Holstein-Primakoff bosonic representation of spin operators. The dynamics is found to be gove rned by a generalized nonlinear Schrodinger equation in the continuum limit . For specific values of the exchange, octupole-dipole interactions, and al so of the anisotropy parameters, through Painleve singularity structure ana lysis, we have identified an integrable spin chain model with soliton spin excitations. We carry out a multiple scale perturbation analysis Co find th e discreteness effect on the soliton excitations in the more general nonint egrable case. [S0163-1829(99)06221-9].