Dynamics of magnetostatic wave solitons in the vicinity of frequency cut-off

Nonlinear dynamics of one-dimensional pulses of exchangeless backward volum e magnetostatic waves propagating in thin ferrite films with a thickness 2l = (3-10)mum is studied numerically. The Whitham's approach of taking into account the exact wave dispersion is utilized. It has been found that in th e case of small wave numbers (0.02 <k(0)l less than or equal to0.05), even under a validity of quasi-statio nary approximation, a commonly used polyno mial approximation for the wave dispersion gives only rough description for nonlinear pulse dynamics. The reason is a presence of cut-off at higher fr equencies. For greater wave numbers (k(0)l greater than or equal to0.1), th e nonlinear wave dynamics coincides with results obtained earlier in the pa rabolic approximation for the wave dispersion. Two-dimensional dynamics of nonlinear pulses is also investigated briefly in the full dispersion approa ch. The collapse-like phenomena have been found there when the central wave number is chosen as k(0)l greater than or equal to0.04. (C) 2001 Elsevier Science B.V. All rights reserved.