Stability And Dynamic Behavior Of Target Skyrmion

Since Tony Skyrme found the skyrmion,the scientists focus on the stability and dynamic behavior.It is a spin stabilized structure with topology protection,like a particle.Because of its small size,high density,speed,it has a great application prospect in the aspect of data storage.We mainly use micromagnetic simulation and numerical calculation method in this paper,we research the evolution of magnetic configuration with perpendicular magnetic field and polar modulation of target skyrmion in nanodisk.On the one hand,we realize controlling the central polarity of target skyrmion by changing the angle of magnetization at the boundary of the nanodisk.On the other hand,we research the evolution of magnetic configuration with perpendicular magnetic field.First of all,we considered to realize the control of central polarity of target-skyrmion by changing the angle of magnetization at the boundary of the nanodisk.We obtain the K-?s diagram of FeGe nanodisk with different radius.When the angle of magnetization at the boundary ranges from 0° to 360°,for small size nadodisk,the equilibrium state presents four states,they are target skyrmion(p=-1)?incompelte skyrmion(p=1)?target skyrmion(p=-1)and incompelte skyrmion(p=1).For large size nanodisk,the incomplete skyrmion state disappeares,the equilibrium state presents two states,they are target skyrmion(p=-1)and target skyrmion(p=-1).So we find that different polarity of target skyrmion can be obtained by controlling the orientation of magnetization at the boundary of the nanodisk.At the same time,we 'simulated the magnetic configuration of FeGe nanodisk with different radius in different boundary condition,the simulation results are in good accordance with the analytical results,The simulation results further verify the analytical results.Secondly,we simulated the ground state with different anisotropies in nanodisk.When the anisotropy ranges from-1×106 J/m3 to 1×106J/m3,the ground state of nanodisk evolves from edged-vortex state to target skyrmion state without external magnetic field,target skyrmion state finally annihilate and translate to the ferromagnetic state.Subsequently,we calculate the evolution of the ground state in nanodisk with perpendicular magnetic field.We obtain the Hz-K diagram phase.The anisotropy plays a very important role in determining evolution of the magnetic state with the perpendicular magnetic field in a nanodisk.Large in-plane anisotropy favors a edged-vortex state.The target skyrmion state can survive in anisotropy ranging from-1.7×105 to 0.6×105 J/m3.Although the disk presents different initial magnetization states at different K,they will transfer to the target skyrmion state with different intermediate states,and finally evolves to ferromagnetic state with the annihilation of the target skyrmion state.The annihilation field decreases with increasing of K.Then for K>1x105 J/m3,the target skyrmion state directly annihilates to the ferromagnetic state.The annihilation field are very smaller than the cases of target skyrmion state,and it increases with K.