The Study Of Skyrmions In Low-Dimensional Helimagnets Using Monte Carlo Method

Magnetic nanomaterial has become a hot topic in nanotechnology research because of their rich physical connotation and wide application prospects.Among them,helimagnet with non-central symmetric structure has always been a frontier in the field of magnetic materials,due to the rich physics originates from the coupling of a variety of free degrees like orbit,spin,and lattice.In 2009,magnetic Skyrmion with stable topology has been found in experiments in MnSi for the first time.The advantageous of Skyrmion are small size,good stability and easy control,lay a foundation for the design of high speed,high density and low energy consumption magnetic storage devices.An in-depth study on the properties and laws of Skyrmion is the key to promote its practicability.In this paper,the Monte-Carlo simulation was used to investigate the nucleation and evolution of Skyrmion in low-dimensional Helix magnets.The effects of magnetic fields and interactions were also explored.The specific research content and results are as follows:The magnetization behavior of SW system was simulated by the improved Monte Carlo simulation and solved by analytical method under the preconditions that the thermal disturbance and the specific magnetization reversal path were fully considered.Angular dependence of the spin textures in two-dimensional chiral magnets has been studied by Monte Carlo method.It is found that,when there is an angle between the magnetic field and the normal direction of the film,Skyrmions change their spin orientations in order to enlarge the angle of their existence.In addition,uniaxial anisotropy plays a positive role in stabilizing the distorted Skyrmions.The magnetization process and microstructure of helimagnet nanostrip and square monolayer were studied.The effects of dimension,exchange,dipole interaction and uniaxial anisotropy on magnetic structure were analyzed:(1)The magnetization process of the nanostrip is similar to that of the two-dimensional film.But restricted by dimension,large stable vortex is formed at the boundary.The rotation direction of Vortex is exactly opposite to that of Skyrmion,which results in the decrease of the average topological charge of the system.(2)The increase of dipole interaction increases the vortex area and makes the system more difficult to magnetize,thus enlarging the magnetic field range of the Skyrmions,but the number of Skyrmions is significantly reduced.(3)Under the influences of dipole interaction and uniaxial anisotropy,the ground state of the square film takes five forms:Helix,Stripe,Edged Vortex,Intermediate and Vortex.When the ground state is Vortex or Stripe,no Skyrmion will be present.The arrangement of Skyrmions in any other ground state is symmetric under the influence of structural symmetry.(4)Uniaxial anisotropy simplifies the magnetization process,allowing a small external magnetic field to induce the transformation of the magnetic phase.