Collective dynamical skyrmion excitations in a magnonic crystal

Abstract

We investigate theoretically skyrmion magnonic crystal, i.e., the dynamics of the magnetization in a chain of the ferromagnetic nanodots being in skyrmion magnetic configuration. We show that collective excitations are possible to be observed in the structure. We present the dispersion relation of the coupled skyrmions. It exhibit a periodical property in dependence on wave vector, characteristic feature of the band structure in magnonic crystals. Spatial analysis of the magnetization amplitude associated with the magnonic bands confirms type of the excited modes, as breathing and clockwise gyrotropic dynamical skyrmions. These high and low frequency excitations, propagate with negative and positive group velocity, respectively, and can be explored for study fundamental properties and technological applications in spintronics and magnonics.

Coupled gyration modes in one-dimensional skyrmion arrays in thin-film nanostrips as new type of information carrier

“…1(a), a single skyrmion of downward core orientation in a 40 nm-wide square dot of thickness of h  = 1 nm. Sinc-function fields, denoted as H  =  H 0  sin[ ω H ( t  −  t 0 )]/[ ω H ( t  −  t 0 )] with H 0  = 10 Oe, ω H  = 2 π  × 50 GHz, and t 0  = 1 ns were applied along the y or x (in-plane25) and z (out-of-plane2325) axis during a time period of t =  100 ns. The main features obtained by applying the fields along the y and x axes are the same.…”

Spin excitation spectrum in a magnetic nanodot with continuous transitions between the vortex, Bloch-type skyrmion, and Néel-type skyrmion states

“…Non zero-frequency modes are expected for the solitons in magnetic dots because the soliton energy depends on the soliton position and soliton radius due to existence of the sample edges. Even though several papers have been already published on the skyrmion dynamical excitations in restricted geometry, [19][20][21][22][23] the consensus regarding the classification of the spin eigenmodes over skyrmion background in nanodots has not been reached so far. Also a transition between the dynamical vortex and skyrmion modes has not been explored.…”

Collective magnetic skyrmion gyrotropic modes in a dot chain

“…Simulation of the high frequency dynamics on the background of the periodic array of current induced skyrmions [30] showed drastic changes of the spin wave dispersion. The investigation of collective SW and gyration mode spectra of skyrmions in the linear chain of nanodots [31], and skyrmions periodically ordered in the linear chains in nanostrips [32] confirmed existence of the frequency band structure. The wide frequency bands of the oscillating skyrmions in a chain of touching nanodots with radii R∼15-50 nm was found in [31].…”

“…While the collective modes of the coupled magnetic vortices in the dot lattices [21][22][23][24][25], dot clusters [26,27] and nanopillars [28,29] are sufficiently well explored, the investigation of collective excitations of the coupled skyrmions in patterned nanostructures is in a beginning stage. Recent publications on this subject concern dynamic magnonic crystals [30], gyrotropic and SW modes of the skyrmion dot chains [31], and coupled gyration modes of the skyrmions periodically arranged in nanostrips [32]. Simulation of the high frequency dynamics on the background of the periodic array of current induced skyrmions [30] showed drastic changes of the spin wave dispersion.…”