Micromagnetic Simulation Of Skyrmions Driven By Current Based On Spin-Transfer-Torque Effect

Magnetic skyrmion is a nano-scale vortex magnetic structure,which has great potential in the development and application of spintronic devices.Generally,magnetic skyrmion is often formed in magnetic thin films with broken symmetry and non-centrosymmetric chiral magnetic materials.Magnetic skyrmion with non-trivial topology in real space exhibit complex and peculiar physical properties,which provide a new direction for the study of topological spintronics.Due to its excellent magnetic structure stability,small size,and small driving current density,magnetic skyrmion have attracted great attention in the applications of spin logic and memory devices.How to effectively drive and control the motion of magnetic skyrmion is extremely important to realize the above-mentioned applications.For this reason,the main research contents of this paper are as follows:(1)By micromagnetic simulation method,the motion mechanism of skyrmion driven by current under the effect of spin-transfer torque was studied.At the same time,we further studied the magnetic anisotropy gradient and the design of the thin film with groove structure on the regulation of magnetic skyrmion motion.Firstly,we investigated the magnetic skyrmion motion and its properties driven by different spin-polarized current,and illustrated the relationship between the current density and the velocity of skyrmions motion and deviation angle.The higher the current density,the higher the velocity and deviation Angle of the skyrmion motion.Secondly,we studied the driving mechanism of magnetic anisotropy with gradient uniform variation to the magnetic skyrmion,and the change of the magnetic skyrmion motion velocity with the gradient of magnetic anisotropy.Skyrmion would spontaneously move from a high anisotropic position to a low anisotropic position,and the higher the anisotropic gradient,the higher the velocity would be.Furthermore,we studied the influence of groove steps on the size and the velocity of the magnetic skyrmion motion in the concave groove film structure.Based on the concave groove structure,we study the motion of the magnetic skyrmion driven by current and the gradient of magnetic anisotropy.It is found that in this way,we can not only constrain the trajectory deflection of the magnetic skyrmion,but also obtain a relatively high velocity.(2)Based on the principle of mutual conversion between two-dimensional magnetic domain walls and magnetic skyrmion,an artificial neuron synaptic device based on magnetic skyrmion is designed.The device is driven by a spin-polarized current and can continuously generate new magnetic skyrmion after being transformed into magnetic domain wall.We used a single magnetic skyrmion to simulate synaptic vesicles,and simulate the synaptic function of artificial neurons by generating,manipulating and detecting skyrmion.