Solitons in one-dimensional magnets (invited)

Abstract

We review recent theoretical results on nonlinear excitations in one‐dimensional magnets. We deal with classical magnetic chains in a continuum description and discuss solutions to the full nonlinear equations of motion for ferromagnetic as well as antiferromagnetic exchange and additional single ion anisotropies and external magnetic fields. Easy‐plane ferro‐ and antiferromagnetic chains in an external field breaking the easy‐plane symmetry can be mapped approximately to the Sine‐Gordon chain. We introduce this mapping and discuss the approximation involved. The kink modes of the Sine‐Gordon chain are topologically stable excitations in these magnetic chains whereas in 1d magnets with different symmetries also pulse modes with continuously varying amplitudes are found to exist. We investigate the influence of nonlinear excitations on dynamic correlation functions in Sine‐Gordon‐like magnetic chains at finite temperatures. Kinks lead to a characteristic broadening of Bragg peaks in antiferromagnets and to a central peak in the dynamic response function of the xy ferromagnet. The latter is shown to be modified considerably by the lowest order corrections to the noninteracting kink/magnon approach.