ملخص: We have carried out a theoretical study of the localized spin-wave modes near the surface step of the insulating Heisenberg antiferromagnet. In this work, we study the full magnetic problem arising from the absence of translational symmetry due to the presence of a magnetic surface and step. The calculation concerns in particular the spin fluctuation dynamics and employs the matching procedure in the random-phase approximation. Only the nearest neighbours exchange interactions are considered between the spins in the model. The analytical formalism presented here determines the bulk and evanescent spin fluctuation fields in the two-dimensional plane normal to the surface and step regions. The results are used to calculate the localized modes of magnons associated with the step and surface terraces. The present model may be generalized to treat the spin fluctuations dynamics of other extended surface imperfections or nanostructures, provided they preserve the translation symmetry of the ordered spins along a direction in the surface boundary. We show the presence of acoustic and optical localized magnon modes propagating along the surface and the step as well as the interface surface-step, their fields is also described as evanescent in the plane normal to the surface step layer and depends on the nature of the bulk-surface and bulk-step coupling exchanges.

لغة: إنجليزية