Imaging magnetic skyrmions with high spatial resolution reveals fine structures

Skyrmions, quasiparticles consisting of topologically stable field configurations, have been theorized to exist since the 1960s. While initially proposed in the context of particle physics, magnetic skyrmions are of interest today because of their potential technological applications in stable and energy-efficient data storage. They were first discovered experimentally in magnetic materials in 2009.

In Applied Physics Letters, an international team of physicists reports its study of magnetic skyrmions with high spatial resolution using off-axis electron holography. They measured and interpreted the local magnetization distributions of skyrmions in an FeGe thin film using a new, model-based, iterative reconstruction method. Their experimental and theoretical results illustrate the physics of magnetic skyrmions.

The group, which specializes in magnetic imaging, performed off-axis electron holography in a transmission electron microscope while a pre-calibrated, out-of-plane magnetic field was applied to the sample. The results reveal the fine structure of magnetization in hexagonal skyrmions in a close-packed honeycomb lattice. The skyrmions transform to circular shape upon magnetic saturation. The magnetization distribution between adjacent skyrmions shows an unexpected modulation of the magnetic spins.

To verify the experimental results, micromagnetic simulations were performed using a classical model for an isotropic chiral magnet. The in-plane components of magnetization found using simulations agreed well with the experimental measurements.

This study increases our understanding of skyrmions and of prospects for their application in skyrmion-based magnetic recording media. According to authors András Kovács and Nikolai Kiselev, the team will move from a static approach to dynamic experiments involving manipulating and moving skyrmions around a magnetic track in situ in the transmission electron microscope.

Source: “Mapping the magnetization fine structure of a lattice of Bloch-type skyrmions in an FeGe thin film,” by András Kovács, Jan Caron, Andrii S. Savchenko, Nikolai S. Kiselev, Kiyou Shibata, Zi-An Li, Naoya Kanazawa, Yoshinori Tokura, Stefan Blügel, and Rafal E. Dunin-Borkowski, Applied Physics Letters (2017). The article can be accessed at https://doi.org/10.1063/1.5004394 .