Study On Magnetization Inversion Process Of Current-driven Perpendicular Magnetic Anisotropic Ferromagnets

In recent years,with the development of science and technology,the performance of magnetic memory has also been improved,and the way of writing information has also changed from the Oersted field generated by the current to the spin transfer torque to the current research hot topic-spin Orbital moment,magnetic memory devices have received extensive attention due to their outstanding performance advantages.However,there is still a lack of systematic research on the performance differences between different flipping methods and the specific flipping process,and the phenomenon of partial flipping in large-scale devices still needs to be explained.In this paper,the microscopic process of current-driven magnetization reversal in perpendicular magnetic anisotropic ferromagnets is investigated mainly by means of macroscopic spin simulations,micromagnetic simulations and experimental measurements.The main research contents are as follows:(1)Using the macroscopic spin model,the conditions,process,and time of magnetic moment inversion were studied when the magnetic field,STT,and SOT were used as driving forces.The origin of the shape of the magnetic moment trajectory.Calculations show that the speed at which SOT drives magnetization reversal is much greater than that of magnetic field and STT,and this difference stems from the fact that SOT mainly contributes to the torque z component,rather than the in-plane component.Unlike STT,SOT requires an auxiliary field to break the flip symmetry to induce a deterministic flip of the magnetic moment.(2)The current-generated SOT-driven magnetization inversion process in the Ta/Pt/[Co/Ni]_nCo/Ta system was investigated by experiments and micromagnetic simulations.Magneto-optical Kerr microscopy observations indicate that the film's magnetization inversion is accomplished by nucleation at the device edge first,followed by domain wall movement.The experimental phenomenon is reproduced by micromagnetic simulation,and the two-dimensional distribution model of magnetic moment is analyzed and proposed,which explains the phenomenon of domain wall tilt and asymmetric expansion in two-dimensional devices.