Coupled Band Gap Solitons in One-Dimensional Alternating Heisenberg Ferromagnetic Chains**The project supported by the Trans-Century Training Programme Foundation for the Talents by the Education Ministry of China and National Natural Science Foundation of China under Grant No. 19975019

Abstract

The dynamics of coupled band gap solitons in one-dimensional Heisenberg ferromagnetic chains with bond alternation is considered analytically. Using the method of multiple scales the nonlinear coupled-mode equations (i.e. Manakov equations) for the upper cutoff mode of acoustic band and the lower cutoff mode of optical band are derived under the quasi-discreteness approximation. Due to the cross-phase modulation the type of soliton excitations may be changed and the vibrating frequencies of these soliton excitations may locate within or outside the gap of magnon frequency bands.