Soliton dynamics in a magnetic chain. I. Antiferromagnet

We study theoretically the effects of the soliton-soliton collision and the soliton-magnon collision in an antiferromagnetic chain in a magnetic field perpendicular to the chain direction. We find that the soliton-soliton collision flips the sign of the magnetization carried by solitons, which leads to the magnetization damping. In addition, the collision gives rise to soliton diffusion. The present theory accounts for the broadening of the parallel spin-correlation function of tetramethyl ammonium manganese trichloride recently observed by Boucher et al.