Magnetic vortex dynamics in interacting micromagnets

Abstract

We have studied magnetic vortex oscillations in circular LSMO (lanthanum strontium manganite) disks by micromagnetic simulations. The simulations were performed using the MuMax3 software developed at the DyNaMat group (Dynamics of Functional Nano Materials) at Ghent University.

A magnetic vortex confined in a magnetically soft ferromagnet with micron-sized lateral dimensions possesses a characteristic dynamic excitation known as the translational mode. Initial simulations focused on investigating this rotation of a vortex core around its equilibrium position. Calculations of the eigenfrequencies, extracted through a Fourier transform of the temporal oscillations of the average magnetization distribution, proved to be in agreement with analytical predictions.

Further simulations focused on investigating vortex-vortex interactions, in order to verify the analogy with electrostatics predicted by condensed matter theory. This was done by mapping the respective trajectories of two vortices confined in two overlapping micron-sized disks. A rudimentary method for quantifying this interaction was introduces, based on aspect ratio of the horizontal and vertical diameters of a given trajectory.

Comparing the trajectories for vortices with different rotational modes, as well as for different center-to-center distances between the ferromagnetic disks, a repulsive interaction was verified.