Filming the formation and fluctuation of Skyrmion domains by cryo-Lorentz Transmission Electron Microscopy

TL;DR

This study uses cryo-Lorentz Transmission Electron Microscopy to directly observe the formation, domain fluctuations, and effects of defects on skyrmion lattices in a Cu2OSeO3 crystal, revealing new insights into their stability and phase transitions.

Contribution

It provides the first real-time, direct-space imaging of skyrmion domain dynamics and phase transitions in a large crystal, highlighting the role of dislocations and defects.

Findings

Discovered a glassy skyrmion phase at the transition field.

Observed domain switching caused by dislocations.

Filmed temporal fluctuations of skyrmion domains.

Abstract

Magnetic skyrmions are promising candidates as information carriers in logic or storage devices thanks to their robustness, guaranteed by the topological protection, and their nanometric size. Currently, little is known about the influence of parameters such as disorder, defects or external stimuli, on the long-range spatial distribution and temporal evolution of the skyrmion lattice. Here, using a large (7.3x7.3{\mu}m$^{2}$) single crystal nano-slice of Cu$_{2}$OSeO$_{3}$, we image up to 70,000 skyrmions, by means of cryo-Lorentz Transmission Electron Microscopy as a function of the applied magnetic field. The emergence of the skyrmion lattice from the helimagnetic phase is monitored, revealing the existence of a glassy skyrmion phase at the phase transition field, where patches of an octagonally distorted skyrmion lattice are also discovered. In the skyrmion phase, dislocations are shown to cause the emergence and switching between domains with different lattice orientations and the temporal fluctuations of these domains is filmed. These results demonstrate the importance of direct-space and real-time imaging of skyrmion domains for addressing both their long-range topology and stability.