Magnetoelastic soliton excitation in a quasi-one-dimensional antiferromagnet

It is shown that in a linear antiferromagnetic chain of spins that interact with lattice vibrations there is an excitation corresponding to a soliton solution of the nonlinear equation for the amplitude of the spin deviations at the sites. In contrast to a ferromagnetic chain, in which the nonlinear Schrödinger equation is obtained for the amplitude, in the antiferromagnetic case there is a nonlinear wave equation. However, the soliton solutions of the two equations are similar, though the expressions for the basic soliton parameters – width, amplitude, and precession frequency – are different, this being due to the fact that the spin wave dispersion laws in the two cases are different. Anisotropy plays an important part. A soliton solution is obtained for easyaxis anisotropy.