Investigation Of Vortex Domain Wall Dynamics In Magnetic Nanostructure Systems

The static and dynamic properties of domain walls in ferromagnetic nanowires have received extensive concern,due to the application prospect in high-density memory and logic devices,and nanowire based microwave generators.In this paper,micromagnetic simulation was conducted to investigate the dynamic of vortex domain walls(VDW)in ferromagnetic nanowires.Firstly we studied the dynamic of vortex domain wall driven by magnetic field which are above the Walker field.Then we investigated the influence of the initial state on the dynamic of domain wall driven by magnetic field.Finally we studied the influence of current on the oscillation process of vortex domain wall driven by field which are above the Walker field.Some important results were obtained and shown as followed:(1)The dynamic behaviors of VDW strongly depend on the geometrical dimensions of nanowires.Under proper dimensions,a VDW driven by a field above Walker field may subject a chirality switching during the oscillation process.The switch of chirality can be manipulated by magnetic field or damping constant.This finding suggests that by selecting proper nanowire dimensions,the state of VDW may be conveniently to manipulate by magnetic field.(2)The propagation and oscillation of VDW with different initial state were investigated.It was found that the propagation speed and the oscillation frequency of VDW domain show some dependence on the initial state of VDW.Deep analysis found that the dependence is actually related to the handedness of the VDW.VDWs with the same handedness show exactly the same dynamic behaviors,while for those with different handedness,the dynamic behaviors are slightly different.Further research should be carried out to find the behind physics for this handedness dependence of VDW dynamic behaviors.(3)Small current was introduced in nanowire and the effects of current on the VDW driven by magnetic field were investigated.It was found that current not only slightly tunes the oscillation frequency but also affects the stability of the VDW.As the increase of applying of current,antivortex domain walls may appear in the oscillation process.