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Magnetic skyrmions have the potential to provide solutions for low-power, high-density data storage and processing. One of the major challenges in developing skyrmion-based devices is the skyrmions' magnetic stability in confined helimagnetic nanostructures. Through a systematic study of equilibrium states, using a full three-dimensional micromagnetic model including demagnetisation effects, we demonstrate that skyrmionic textures are the lowest energy states in helimagnetic thin film nanostructures at zero external magnetic field and in absence of magnetocrystalline anisotropy. We also report the regions of metastability for non-ground state equilibrium configurations. We show that bistable skyrmionic textures undergo hysteretic behaviour between two energetically equivalent skyrmionic states with different core orientation, even in absence of both magnetocrystalline and demagnetisation-based shape anisotropies, suggesting the existence of novel Dzyaloshinskii-Moriya-based shape anisotropy. We also show that the skyrmionic texture core reversal dynamics is facilitated by the Bloch point occurrence and propagation. Finally, we report the resonance frequencies and corresponding normal modes of all identified equilibrium states as well as how the resonance frequencies change depending on both the external magnetic bias field and disk sample diameter.

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Marijan Beg, University of Southampton
Seminar room 0.03, ETP
Contact: Markus Garst