The soliton response occurring at elevated temperatures in the one-dimensional Ising-type antiferromagnet CsCo${\mathrm{Br}}_3$ has been studied by neutron scattering. An inelastic peak is observed and identified as the Villain mode arising from the propagation of domain walls. Calculations have been made of the response from domain-wall-pair states and an extension of the first-order perturbation theory derived by Ishimura and Shiba. A reasonable account is obtained of the observed polarization and intensity of the scattering. The effect of collisions is seen to be increasingly important as the temperature is raised. The response near the zone center has been compared with the ideal-soliton-gas theory of Maki. The theoretical prediction, which has the form of a Lorentzian raised to the power $\frac{3}{2}$, gives a good qualitative description of the temperature dependence of the intensity and width of the scattering.

• Received 17 January 1983

DOI:https://doi.org/10.1103/PhysRevB.28.3873