SOLITONS ON LOW-DIMENSIONAL ANTIFERROMAGN ETS

The structure, dynamics, and thermodynamics of magnetic solitons in lo w-dimensional antiferromagnets (AFM) are considered from the common vi ewpoint. The primary attention is given to the models for which experi mental data are available. The analysis is based on simple phenomenolo gical equations describing the dynamics of AFM in terms of the unit ve ctor of antiferromagnetism, in the simplest case the equations reducin g to the form of a Lorentz-invariant sigma-model (the chosen velocity is the phase velocity of spin waves). Lowering the symmetry of AFM, e. g., in presence of an external magnetic field or when taking into acco unt the Dzyaloshinskii interaction, violates the Lorentz-invariance. T he finite-velocity transformation of the kink structure and its influe nce on the soliton thermodynamics of one-dimensional AFM are discussed . Semiclassical quantization of soliton solutions is carried out. It i s demonstrated that the dynamics of internal kink degrees of freedom i n a one-dimensional AFM is of a quantum nature, which is important whe n considering two-parametric solitons (bions) in almost easy-axis AFM. Two-dimensional topological solitons of the type of localized and non -localized magnetic vortices and their contribution to the thermodynam ics of two-dimensional AFM are considered. The current state of the pr oblem of experimental observation of magnetic solitions in quasi-two-d imensional AFM is reported; possible directions of future research are outlined.