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

由本征和/或诱导的Dzyaloshinskii-Moriya(DM)相互作用稳定的轴对称孤子(手性Skyrmions)和由表面退磁效应稳定的普通圆柱形磁畴(气泡)是在最近合成的磁性化合物纳米层和多层堆栈中观察到的两种根本不同类型的拓扑非平凡磁性结构。它们包含位于纳米到微米尺度的斑点中的反磁化区，因此被认为是新型磁数据存储和新兴自旋电子中的其他应用的有前途的对象。最近，在许多类型的纳米层中观察到了一种不同类型的局域磁图案--在手性DM和磁偶极相互作用的共同影响下形成的。这些特殊的局域态代表了在非中心对称铁磁体的纳米层中发现的“纯”手性Skyrmions和在具有强垂直各向异性的铁磁薄膜中出现的经典泡状区之间的中间物体。这些结构可以被认为是具有手性天离子和磁区性质的“天离子-气泡杂化材料”。在这个项目中，我们将发展一种理论，在最近合成的具有中等或微弱垂直各向异性的纳米磁系统中出现相应的局域态和调制态，以及由于DM相互作用而产生的本征和/或诱导手性调制。分析理论研究将与使用高分辨率磁光克尔显微镜和全尺寸先进微磁模拟的磁区观察相结合。基于我们的理论和实验结果，我们打算对现代纳米磁性材料中的气泡-Skyrmion态进行全面的物理描述，这些材料具有本征和诱导手性相互作用。

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.