Magnetic skyrmions-bubble hybrids in nanolayers of metallic ferromagnets: interplay of the magnetodipolar and Dzyaloshinskii-Moriya interactions

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Axisymmetric solitons stabilized by intrinsic and/or induced Dzyaloshinskii-Moriya (DM) interactions (chiral skyrmions) and common cylindrical magnetic domains (bubbles) stabilized by surface demagnetization effects are two fundamentally different types of topologically non-trivial magnetic structures observed in recently synthesized nanolayers and multilayer stacks of magnetic compounds. They contain areas of reversed magnetization localized in spots of the nano- to microscale size and thus are considered as promising objects for novel types of magnetic data storage and other applications in emerging spin electronics. Recently, a different kind of localized magnetic patterns – formed under the combined influence of chiral DM and magnetodipolar interactions – has been observed in many types of nanolayers. These specific localized states represent intermediate objects between "pure" chiral skyrmions found in nanolayers of non-centrosymmetric ferromagnets and classical bubble domains arising in ferromagnetic films with strong perpendicular anisotropy. These structures can be considered as "skyrmion-bubble hybrids" exhibiting properties attributed both to chiral skyrmions and magnetic domains. Within this project we shall develop a theory of corresponding localized and modulated states arising in recently synthesized nanomagnetic systems with moderate or weak perpendicular anisotropy and intrinsic and/or induced chiral modulations due to the DM interaction. Analytical theoretical research will be combined with domain observation using high-resolution magneto-optical Kerr microscopy and full-scale advanced micromagnetic simulations. Based on our theoretical and experimental findings we intend to create a comprehensive physical description of the bubble-skyrmion states arising in modern nanomagnetic materials with intrinsic and induced chiral interactions.