# Fluctuations and Noise Signatures of Driven Magnetic Skyrmions

## TL;DR

This paper investigates how driven magnetic skyrmions exhibit velocity fluctuations and noise signatures due to disorder and the Magnus force, revealing a transition to a moving crystal state at high drives.

## Contribution

It introduces a particle-based simulation model that captures the effects of Magnus force and disorder on skyrmion dynamics, highlighting the formation of a moving crystal phase.

## Key findings

- Velocity fluctuations are isotropic at high drives.
- Spectral analysis reveals dynamical phase transitions.
- Velocity noise correlates with skyrmion Hall angle and lattice structure.

## Abstract

Magnetic skyrmions are particle-like objects with topologically-protected stability which can be set into motion with an applied current. Using a particle-based model we simulate current-driven magnetic skyrmions interacting with random quenched disorder and examine the skyrmion velocity fluctuations parallel and perpendicular to the direction of motion as a function of increasing drive. We show that the Magnus force contribution to skyrmion dynamics combined with the random pinning produces an isotropic effective shaking temperature. As a result, the skyrmions form a moving crystal at large drives instead of the moving smectic state observed in systems with a negligible Magnus force where the effective shaking temperature is anisotropic. We demonstrate that spectral analysis of the velocity noise fluctuations can be used to identify dynamical phase transitions and to extract information about the different dynamic phases, and show how the velocity noise fluctuations are correlated with changes in the skyrmion Hall angle, transport features, and skyrmion lattice structure.