The static and dynamic states of Néel skyrmions in ultrathin ferromagnetic films with interfacial Dzyaloshinskii-Moriya interaction (DMI) have been micromagnetically simulated as functions of the interfacial DMI strength and applied static magnetic field. Findings reveal that while the breathing, counterclockwise (CCW) and clockwise (CW) rotational eigenmodes exist in the skyrmion lattice (SkL) phase, only the first two modes are present in the isolated skyrmion (ISk) phase. Additionally, the eigenfrequency of the CCW mode is insensitive to the magnetic-field driven SkLISk phase transition, and the inter-skyrmion interaction is largely responsible for exciting the CW mode in the SkL phase. The findings provide physical insight into the dynamics of the phase transition and would be of use to potential skyrmionbased microwave applications.
Brillouin measurements of the dispersion relations of surface acoustic-and optical-like waves along CM and C-X symmetry directions in a two-dimensional bicomponent nanostructured crystal are reported. The sample, in the form of a periodic chessboard array of alternating Permalloy and cobalt square dots on a SiO 2 /Si substrate, was fabricated using high-resolution electron-beam lithographic, sputtering, etching, and lift-off techniques. The measured phononic band structures exhibit diverse features, such as a partial hybridization bandgap and unusual surface optical-like phonon branches, where there are out-of-phase vibrational characteristics between nearest-neighbor dots. Numerical simulations, based on the finite element analysis, reproduced the experimental dispersion relations.
The band structures of surface acoustic waves in nanostructured phononic crystals with defects have been studied by Brillouin light scattering and finite-element simulations. The crystals are one-dimensional periodic arrays of alternating gold stripes and air gaps on SiO2/Si substrates, where the periodic defects are gold stripes with non-regular widths. The general features of the band structures are similar to those of the perfect crystal, with the main difference being the appearance of nearly dispersionless defect branches within the bandgap. The defect modes exhibit localization features and are frequency-tunable by varying the defect stripe size.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.