Non-collinear three-dimensional textures in magnetic multilayers: Hatching of skyrmionic cocoons

Two-dimensional magnetic textures such as skyrmions or chiral domain walls were mostly under focus for the last decade, but recently interest has surged for more complex objects which display an inhomogeneous behavior over the vertical dimension. Interesting examples include bobbers which could become remarkable assets for the development of logic devices [1] or the recently observed hopfions [2] or even different skyrmions phases[3]. In this study, we engineer and explore three-dimensional textures allowed us to observe the signature of potential new textures, which we will name skyrmionic cocoons. At low magnetic field, they resemble tubular skyrmions but upon an increase of the out-of-plane field, they shrink and disappear in the outer layers becoming elongated ellipsoids. By carefully tuning the thickness of each magnetic layer, it is possible to observe in a single sample two distinct objects, as shown by the strong difference in the Magnetic Force Microscopy (MFM) contrasts. With the support of micromagnetic simulations, we identify them as two vertically coupled cocoons (large contrast) and single cocoons only present in half of the layers (weak contrast). The existence and field-dependent behavior of such textures could represent interesting possibilities for potential applications.

[1] Zheng, Fengshan, et al. arXiv preprint arXiv:1706.04654 (2017).

[2] Kent, Noah, et al. Nat. comm. 12.1 (2021).

[3] Mandru, Andrada-Oana, et al. Nat. Comm. 11.1 (2020).