How hole defects modify vortex dynamics in ferromagnetic nanodisks

TL;DR

This paper investigates how small cylindrical holes in ferromagnetic nanodisks influence vortex magnetization dynamics, revealing significant shifts in oscillation frequencies and core behavior due to defect interactions.

Contribution

It provides analytical insights into the effects of cavities on vortex oscillations and core dynamics, a novel exploration of defect-induced modifications in nanomagnetism.

Findings

Vortex gyrotropic frequencies decrease when nucleated from the hole.

Core capture by the hole significantly alters vortex dynamics.

The gyrovector can be suppressed, increasing oscillation frequencies.

Abstract

Defects introduced in ferromagnetic nanodisks may deeply affect the structure and dynamics of stable vortex-like magnetization. Here, analytical techniques are used for studying, among other dynamical aspects, how a small cylindrical cavity modify the oscillatory modes of the vortex. For instance, we have realized that if the vortex is nucleated out from the hole its gyrotropic frequencies are shifted below. Modifications become even more pronounced when the vortex core is partially or completely captured by the hole. In these cases, the gyrovector can be partially or completely suppressed, so that the associated frequencies increase considerably, say, from some times to several powers. Possible relevance of our results for understanding other aspects of vortex dynamics in the presence of cavities and/or structural defects are also discussed.