PARAMETRICALLY FORCED SINE-GORDON EQUATION AND DOMAIN-WALL DYNAMICS IN FERROMAGNETS

A parametrically forced sine-Gordon equation with a fast periodic mean -zero forcing is considered. It is shown that pi kinks represent a cla ss of solitary-wave solutions of the equation. This result is applied to quasi-one-dimensional ferromagnets with an easy-plane anisotropy, i n a rapidly oscillating magnetic field. In this case the pi-kink solut ion we have introduced corresponds to the uniform ''true'' domain-wall motion, since the magnetization directions on opposite sides of the w all are antiparallel. In contrast to previous work, no additional anis otropy is required to obtain a true domain wall. Numerical simulations showed good qualitative agreement with the theory.