Neel Skyrmionic States and Chiral Stripes in the Magnetic Bilayer with Transverse Easy Axis

Chiral spin structures, such as skyrmions, are topologically nontrivial magnetization configurations, which have potential applications in magnetic recording media. In particular, an antiferromagnetically coupled system that hosts skyrmions is of great interest because of high-speed skyrmion motion and reduced skyrmion Hall effect. Here, we consider TbCo/GdFe-based amorphous ferrimagnetic system showing chiral stripe domains and Neel-type skyrmions. It is observed that skyrmionic configurations are stabilized with the help of dipolar interactions that exist in the system. Optimized thicknesses of TbCo (30 nm) and GdFe (6 nm) show isolated skyrmions in both the layers with average skyrmion diameter of 40 +/- 5 nm. We have also investigated a phase diagram in a wide range of layer thickness, which represents the presence of the mixture of either vortex, chiral stripes, or/and Neel-type skyrmions. To understand the underlying phenomena which help chiral ferrimagnetism in this kind of amorphous system, we perform layer-resolved micromagnetic modeling. We found variety of chiral textures in a wide thickness range of ferrimagnetic bilayer systems, which may be useful for fundamental understanding of formation of skyrmion and their application in spintronic devices.