Study On Stability Of Skyrmions In FeGe Nanotubes And Curved Surfaces

Skyrmion is a topologically stable spin structure on the nanometer scale.Due to its topological protection,it has high structural stability and can be driven by a lower current.Therefore,it can be used as an information carrier for magnetic memory devices.In the future,high-speed,high-density,low-energy,and non-mechanical information storage will be realized.In this paper,the process of generating skyrmion through the z-axis field in FeGe nanotubes and curved surfaces is studied by micromagnetic simulation.We calculated the hysteresis loop of FeGe nanotubes and curved surfaces,summarized the variation law of the topological number,and obtained the conditions of skyrmion generation and analyzed its stability.The details can be summarized as:(1)Nanotubes with an outer diameter of more than 40 nm can produce skyrmions under the action of the z-axis field.The generated skyrmion is located in the nanotube wall in the direction of the outer field and the normal line of the nanotube wall,where in the upper and lower surfaces of the nanotube will produce a completely symmetrical skyrmion.In the zero field,there are spiral domains in the nanotubes.When the external field increases,the magnetic moment on the wall of the nanotube parallel to the external field is first magnetized,which appears as the spiral fringe domain breaks there,and then two above and below the nanotube.The surface forms an independent topological structure,and as the external field continues to increase,the independent topology gradually evolves to form a stable skyrmion.(2)The size has an effect on the generation field and annihilation field of the skyrmion in the nanotube.It can be concluded that the larger the outer diameter of the nanotube,the thinner the wall thickness of the nanotube is,the easier it is to produce the skyrmion,and the range existing in the external field is also the wider the more.At the same time,the maximum number of topologies of nanotubes of different sizes in the magnetization process is different.(3)We studied the magneto-induced loops of curved surfaces with arc lengths fixed at 250 nm and different curvatures.It is found that the evolution of magnetic structures in curved surfaces varies with the radius of curvature.When the radius of curvature is greater than 600 nm,a stable skyrmion can be produced,and the formation process is similar to the generation process of the skyrmion in the plane.Stable skyrmion can also be produced when the radius of curvature is less than 120 nm,but the formation process is similar to the process of producing skyrmion in nanotubes.When the radius of curvature is between 120 and 600 nm,the skyrmion cannot be produced.