3D quasi-skyrmions in thick cylindrical and dome-shape soft nanodots.

[EN] Magnetic skyrmions are widely attracting researchers due to fascinating physics and novel applications related to their non-trivial topology. Néel skyrmions have been extensively investigated in magnetic systems with Dzyaloshinskii–Moriya interaction (DMI) and/or perpendicular magnetic anisotropy. Here, by means of micromagnetic simulations and analytical calculations, we show that 3D quasi-skyrmions of Néel type, with topological charge close to 1, can exist as metastable states in soft magnetic nanostructures with no DMI, such as in Permalloy thick cylindrical and dome-shaped nanodots. The key factor responsible for the stabilization of DMI-free is the interplay of the exchange and magnetostatic energies in the nanodots. The range of geometrical parameters where the skyrmions are found is wider in magnetic dome-shape nanodots than in their cylindrical counterparts. Our results open the door for a new research line related to the nucleation and stabilization of magnetic skyrmions in a broad class of nanostructured soft magnetic materials.E.B. acknowledges the Alexander von Humboldt foundation for a postdoctoral fellowship. M.J. acknowledges the Universidad Autónoma de Madrid and Comunidad Autónoma de Madrid through the project SI1/PJI/2019-00055 and the program “Excelencia para el Profesorado Universitario”, as well as the María de Maeztu Programme for Units of Excellence in R&D (CEX2018-000805-M). K.G. acknowledges support by IKERBASQUE (the Basque Foundation for Science). O.C., A.A. and K.G. work was supported by the Spanish Ministry of Science and Innovation under Grants PID2019-108075RB-C31 and PID2019-108075RB-C33/AEI/https://doi.org/10.13039/501100011033. The research of K.G. was partially supported by the Norwegian Financial Mechanism 2014–2021 trough project UMO-2020/37/K/ST3/02450. Open Access funding enabled and organized by Projekt DEAL