Soliton features in easy-plane ferromagnets?

Numerical transfer-integral and molecular-dynamics calculations are used to demonstrate that the mapping of an easy-plane ferromagnet in a field to the sine-Gordon system fails. The crucial implication for CsNiF3 is that the central peak observed by Kjems and Steiner at T=10 K is more likely to be due to multimagnon difference processes, or pulse-soliton features of the nearly isotropic model rather than due to kink or breather solitons. © 1980 The American Physical Society.