Dynamics of Pinned Magnetic Vortices

TL;DR

This study investigates the behavior of a magnetic vortex interacting with randomly distributed pinning sites, revealing a sharp transition from localized to magnetostatic-determined dynamics due to depinning.

Contribution

It provides the first detailed observation of vortex depinning transition and maps pinning site distribution via frequency fluctuation analysis.

Findings

Vortex gyration frequency depends on pinning at low amplitudes.

A sharp depinning transition occurs at a critical excitation amplitude.

Pinning site distribution can be mapped through frequency fluctuation analysis.

Abstract

We observe the dynamics of a single magnetic vortex in the presence of a random array of pinning sites. At low excitation amplitudes, the vortex core gyrates about its equilibrium position with a frequency that is characteristic of a single pinning site. At high amplitudes, the frequency of gyration is determined by the magnetostatic energy of the entire vortex, which is confined in a micron-scale disk. We observe a sharp transition between these two amplitude regimes that is due to depinning of the vortex core from a local defect. The distribution of pinning sites is determined by mapping fluctuations in the frequency as the vortex core is displaced by a static in-plane magnetic field.