Theory of the soliton-induced phase transition in quasi-one-dimensional magnets.

Abstract

It is shown that the phase transition occurring in quasi-one-dimensional systems of weakly coupled magnetic chains with solitons in the form of \ensuremath{\pi} kinks is closely related to the properties of these solitons. The critical behavior of the systems considered corresponds to the critical behavior of the Ising model with the same dimension. The model describing the behavior of solitons below and above the critical temperature is presented. This model explains the experimental field dependence of the magnetization direction in the spin-flopping configuration for antiferromagnetic ${\mathrm{K}}_{2}$${\mathrm{FeF}}_{5}$. Application of the theory proposed here to the antiferromagnetic tetramethylammonium manganese trichloride (TMMC) allows one to explain the experimental field dependence of the N\'eel temperature.