Theoretical Studies Of Skyrmion's Edge Effect And Kinematical Characteristics

Magnetic materials are an old kind of strong functional materials.As an important branch of magnetic materials,magnetic storage materials have been widely used in daily life.Skyrmions,currently one of the magnetic storage materials with the brightest prospects,are promising candidates as bit carriers for future data storage and logic devices using extremely low energy,with their motion driven by small electrical currents.Skyrmion-based racetrack memory(RM)devices combines non-volatile and energy-efficient qualities along with ultra-high density and negligible ohmic heating,which attracted widespread attention.Based on the three-dimensional micromagnetic simulation software OOMMF(the Object-Oriented MicroMagnetic Framework),this thesis simulates the influence of the edge effect on the skyrmion generation in constrained systems as well as the influence of the kinematical characteristics in periodic racetracks.The main research results are as follows:1.A stabilized skyrmion can be created via vertical spin current injection only when the distance between the spin-polarized current injection region and the end of the nanotrack is larger than a certain threshold(critical distance dc).Beyond this threshold dc,other kinds of spin structures will form and annihilate ultimately when driven by spin current.Different spin structures have different levels of energy,but that of the skyrmion state is the lowest.The skyrmion state only generates under appropriate current densities,magnetic parameters and material parameters.The critical distance dc for the successful generation of multiple skyrmions in the nanotrack is the same as that for the generation of a single skyrmion.2.The kinematic characteristics of the skyrmion in the periodic racetrack were obtained: our results confirm that the transverse drift induced by the Magnus force can be suppressed by the edge material with high magnetic anisotropy.The narrow and wide parts of the racetrack correspond to the peak and valley values of the energy curve,respectively,which is confirmed by the skyrmion relaxation.The skyrmion can pass all the narrow parts in the racetrack without annihilating under the appropriate driving current densities and narrow parts.