Lisa Kern
Topologically non-trivial magnetic solitons—including skyrmions and their higher-order variants —are promising building blocks for next-generation spintronic and unconventional computing technologies [1]. While unit-charge skyrmions have been demonstrated and manipulated across different material platforms, controlled formation of higher-order textures such as skyrmion bags has remained challenging due to the delicate balance of magnetic interactions required for their stabilization [2, 3]. Here, we demonstrate a generalizable pathway to generate, stabilize, and control both conventional skyrmions and higher-order skyrmion bags in ferromagnetic thin films [4]. Using focused He⁺-ion irradiation, we locally modify magnetic anisotropy to create deterministic nucleation centers, shaping the local energy landscape. These engineered regions enable controlled formation of skyrmionium, target skyrmions, and reconfigurable skyrmion bags under magnetic fields or ultrafast laser excitation [5]. High-resolution x-ray microscopy confirms robust stabilization, while micromagnetic simulations reveal the role of defect geometry and the anisotropy step to form multi-skyrmion configurations and closed-loop domains. Skyrmion bags exhibit rich internal degrees of freedom, including shape adaptability and tunable topological charge [6], which can be reconfigured via spin-orbit torques. As anisotropy engineering also locally enhances spin-orbit torque efficiency, skyrmion bags offer prospects for low-power electrical control. Our results establish a scalable, versatile scheme for on-demand creation of higher-order skyrmion textures. Beyond static stabilization, the internal dynamics, reconfigurability, and skyrmion interactions position these textures as promising elements for energy-efficient neuromorphic systems, adaptive sensing, and dynamic information processing. This approach, demonstrated in ferromagnets, can be extended to other materials where anisotropy engineering and enhanced spin-orbit torque efficiency could enable novel physics.
References
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4. L.-M. Kern, V. M. Kuchkin, V. Deinhart, et al., Adv. Mater., 2501250 (2025).
5. L.-M. Kern, B. Pfau, V. Deinhart, et al., Nano Lett., 22(10), 4028-4035 (2022).
6. V. M. Kuchkin, K. Chichay, B. Barton-Singer, et al., Phys. Rev. B, 104(16), 165116 (2021).