SPIN WAVE MODES AND MAGNON SCATTERING AT SURFACE NANOSTRUCTURE ON 2D HEISENBERG FERROMAGNETS

Abstract

We investigate the spin fluctuation dynamics and the scattering phenomena at adsorbed magnetic nanostructure on the surface of two-dimensional Heisenberg ferromagnets. The surface is considered as an infinite slab of two coupled atomic layers, and the nanostructure as an isolated monatomic chain on the surface of a cubic lattice. No electronic effects are considered but local changes in exchange fields between the localized spins of the nanostructure and the magnetically ordered substrate are assumed to be dominant. The mathematical framework of the matching method is used to analyze both the localization and the scattering phenomena at the nanostructure boundaries. The energy of spin wave localized modes arising from the absence of magnetic translation symmetry is determined. The transmission and reflection probabilities as well as the spin wave average transmittance across the nanostructure are calculated and numerical results are presented in a large range of scattering energies. It is shown that there are several localized spin wave modes associated with the nanostructure which may be either optical or acoustical modes (depending on the system parameters), and the coherent coupling between these localized spin modes and the propagating spin modes of the system leads to Fano resonances in the scattering spectra.