Statistical mechanics of a classical one-dimensional canted antiferromagnet. II. Solitons

Abstract

In this paper we continue the study, initiated in the preceding paper, of a classical, one-dimensional, Heisenberg antiferromagnet with a single-ion anisotropy and a Dzyaloshinski-Moriya term. We show that in certain ranges of coupling constants domain walls in such antiferromagnets can be approximated by sine-Gordon or double-sine-Gordon solitons. These solitons can be used to explain certain qualitative features in the low-temperature susceptibility, specific heat, and some correlation functions in such antiferromagnets. However, a simple sine-Gordon or double-sine-Gordon theory cannot reproduce, in any quantitative fashion, the thermodynamic functions obtained in the preceding paper even at low temperatures. We end with some remarks on the feasibility of finding simple, sine-Gordon-type solitons in real, quasi-one-dimensional magnets.