pi-Kinks in the parametrically driven sine-Gordon equation and applications

Parametrically driven sine-Gordon equation with a mean-zero forcing is cons idered. It is shown that the system is well approximated by the double sine -Gordon equation using the normal form technique. The reduced equation poss esses pi-kink solutions, which are also observed numerically in the origina l system. This result is applied to domain walls dynamics in one-dimensiona l easy-plane ferromagnets. For such system the existence of pi-kinks implie s the "true" domain structure in the presence of high-frequency magnetic fi eld. Copyright (C) 1998 Elsevier Science B.V.