Micromagnetic Modeling Of Magnetization Dynamics In Spin-Devices With Titled Spin-polarizer

The magnetic nano-pillar spin device composed of perpendicular magnetic anisotropic material has outstanding advantages such as good thermal stability,lower critical flip current,and less influence by the sample size ratio.For spin devices with perpendicular magnetic anisotropy,the typical structure is that the magnetization of the free layer is perpendicular to the film surface,and the magnetization of the polarized layer has a certain angle with the direction of the perpendicular film surface.The advantage of this structure is that the polarizing layer will exert two in-plane and out-of-plane moments on the magnetization of the free layer.Regulating these two moments can be used to optimize and enhance the spin wave signal.Spin-rotation efficiency,reducing free layer magnetization inversion time,etc.Aiming at such asymmetric spin devices,the main research contents of this paper are as follows.The first part is based on Landau-Lifshitz-Gilbert-Slonczewski(LLGS)equation for the asymmetric magnetic nano-pillar structure where both the free layer and the spin-polarized layer are perpendicular magnetic anisotropic materials.The inversion characteristics of the magnetization in the free layer driven by the external magnetic field and current are also studied.The simulation results show that there are multiple "bulge" abnormal flipping states in the magnetization flipping curve;and the position of the raised area is related to the applied magnetic field size,nano-pillar size,and perpendicular magnetic anisotropy,but to the polarizing layer The inclination of the magnetization has nothing to do with it.When the magnetization inclination angle of the spin polarized layer is given,the final states of the magnetization appearing in the raised region have three modes: metastable,oscillating,and stable.We have established that they change with the change of the magnetic field and the polarization angle of the polarized layer.The phase diagram of the parameter and a simple analysis of the oscillation frequency of the magnetization in the oscillation state.The second part,for the spin device which is driven by the dual-polarizer layer,the advantage is that the magnetization switching time is greatly shortened.Through macro-spin simulation,we studied the effect of the magnitude of the perpendicular torque term in the two polarizers on the magnetization of the free layer;the effect of current density on the criticaltime of magnetization switching of the free layer;The effect of the material's polarization factor on the magnetization flipping behavior of the free layer.The research results show that the necessary conditions for achieving ultra-fast flipping are that the spin torque effect of the perpendicular polarized layer is much smaller than that of the in-plane polarized layer.In the case of this dual-polarized layer driving,the free layer magnetization will have three different dynamic behaviors: stable magnetization switching,magnetization oscillation motion and inability to flip;and the establishment of these three behavioral characteristics with spin torque Phase diagram of relative size.This provides a reliable basis for our next micromagnetic simulation.