# Few-nm tracking of magnetic vortex orbits and their decay with ultrafast Lorentz microscopy

## TL;DR

This paper demonstrates ultrafast Lorentz microscopy to track magnetic vortex orbits at nanometer precision, revealing decay dynamics and frequency changes after current-induced gyration in nanoscale magnetic structures.

## Contribution

It introduces a time-resolved Lorentz imaging method combined with RF excitation for nanoscale magnetic dynamics analysis with nanometer precision.

## Key findings

- Achieved ±2nm localization of vortex core trajectories.
- Observed frequency hardening and increased decay rates after current switch-off.
- Provided insights into vortex behavior influenced by local disorder.

## Abstract

Transmission electron microscopy is one of the most powerful techniques to characterize nanoscale magnetic structures. In light of the importance of fast control schemes of magnetic states, time-resolved microscopy techniques are highly sought after in fundamental and applied research. Here, we implement time-resolved Lorentz imaging in combination with synchronous radio-frequency excitation using an ultrafast transmission electron microscope. As a model system, we examine the current-driven gyration of a vortex core in a 2 $\mathrm{\mu}$m-sized magnetic nanoisland. We record the trajectory of the vortex core for continuous-wave excitation, achieving a localization precision of $\pm$2nm with few-minute integration times. Furthermore, by tracking the core position after rapidly switching off the current, we find a temporal hardening of the free oscillation frequency and an increasing orbital decay rate attributed to local disorder in the vortex potential.