Filming the formation and fluctuation of skyrmion domains by cryo-Lorentz transmission electron microscopy

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 46; pp. 14212 - 14217
• Main Authors: Rajeswari, Jayaraman, Huang, Ping, Mancini, Giulia Fulvia, Murooka, Yoshie, Latychevskaia, Tatiana, McGrouther, Damien, Cantoni, Marco, Baldini, Edoardo, White, Jonathan Stuart, Magrez, Arnaud, Giamarchi, Thierry, Rønnow, Henrik Moodysson, Carbone, Fabrizio
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 17-11-2015; National Acad Sciences
• Subjects: Magnetic fields; Physical Sciences; Single crystals; Topology; Transmission electron microscopy; Lorentz transmission electron microscopy; skyrmions; skyrmion dynamics; strongly correlated systems; magnetic materials
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1513343112

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 (7.3×7.3μm²) single-crystal nanoslice (150 nm thick) of Cu₂OSeO₃, 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 fluctuation 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.