Nonlinear collective excitations in helical magnetic structures

Based on the sine-Gordon model for a quasi-one-dimensional ferromagnet without an inversion center, it is shown that the total set of nonlinear modes of a helical structure contains particle-like solitons and dispersing spin waves. New types of solitons in the helical structure are described. It is found that collisions of solitons with each other are accompanied by variations in the coordinates of their centers and in their phases, as well as shifts of the structure. The possibilities of the diagnostics of solitons in the presence of external magnetic field perpendicular to the axis of the magnetic helix are established. The theoretical description of the nonlinear dynamics of spin waves is reduced to the solution of linear integral equations.