Micromagnetic Simulations of Vortex Resonances in Coupled Nanodisks

Abstract

The high-frequency response of two magnetostatically coupled nanodisks supporting a vortex state within a stack has been investigated by means of 3-D dynamic micromagnetic simulations performed in the frequency domain. These spectra reveal one or two resonance lines according to the vortex polarizations and chiralities. These sub-gigahertz resonance modes are associated with vortex core modes. The magnetostatic coupling controlled by the interdisk distance affects both the structure of the vortex core modes and their associated resonance frequencies. In the regime of strong magnetostatic interaction, coupled vortex core modes are analyzed in terms of the relative phase relation between the vortex core motions. Lastly, the characteristics of the dynamic susceptibility spectra are also strongly dependent on the relative disk thicknesses. It results that these dynamic magnetic couplings play a major role in the high-frequency response of layered magnetic nanostructures and should be taken into account in the design of new spintronic or microwave devices based on vortex dynamics.

Giant moving vortex mass in thick magnetic nanodots

“…3 ) of the fundamental vortex mode varying the dot thickness L are in a very good agreement with the experimental data, demonstrating the similar maximum of the dependence ω 0 ( L ). From the other side, our simulations are in qualitative agreement with the simulations by Boust et al 21 22 for the dots of small radius R = 80 nm. This allows us to consider the conducted micromagnetic simulations as a reliable tool to study in details the observed vortex excitation modes in thick dots.…”

Two-body problem of core-region coupled magnetic vortex stacks

“…In agreement with Ref. [32] the case of equal circularities provokes a larger static displacement of the cores. Depending on the geometry of the disks, the displacement is expected to emerge for the case of different circularities as well.…”

“…Stacking the vortices allows for a strongly increased packing density and has thus stimulated recent studies [23][24][25][26][27][28][29][30]. While for two-dimensional arrangements the minimization of the stray fields at the side surfaces creates the vortices and mediates their interaction, we observe a second coupling mechanism for three-dimensional stacks that has been investigated theoretically [26,31,32]. Due to core coupling the collective motions in an elementary stack of two vortices become a two-body problem.…”

“…2, which can be explained by the overestimation of the rigid vortex approach [38]. Still, the observed repulsion of the vortex cores has to be taken into account [26,31,32]. Therefore, we performed calculations where the interaction of the vortex cores is modeled by an additional potential.…”