Research On Magnetization Reversal Driven And Dynamics By Spin-obrit Toque

In recent years,current driven spin-torque magnetic random-access memory（STT-MRAM）and spin-orbit torque magneticrandom-access memory（SOT-MRAM）have greatly reduced energy consumption and shortened the time taken for magnetization switching compared with traditional magnetic field-driven perpendicular magnetization switching.Spin-orbit torques（SOTs）provide an effective way of electrically manipulated magnetization switching and information writing for read/write separation,and the spin-orbit torque-type magnetic random-access memory（SOT-MRAM）based on the SOT effect is expected to become the key technology of the next generation of low-power and high-speed non-volatile memory.Therefore,improving the efficiency of the material’s own spin-orbit torque to further achieve efficient and controllable magnetic domain wall motion has become the focus of spintronics research.We used magnetron sputtering technology to prepare heavy metal/ferromagnetic layer multilayers,heavy metal/ferrimagnetism heterojunctions,and two-dimensional material heterojunctionswith perpendicular magnetic anisotropy（PMA）.The spin-orbit torquemagnetization switching of the heterojunction system was studied by electrical transport measurements,and the magnetic domain wall motion was investigated by combining techniques such as magneto-optical kerr microscopy,The following is the research content of this paper and the corresponding results obtained.（1）Using magnetron sputtering technology,under a substrate pressure of less than 5×10^-8 Torr,deposited on a thermally oxidized Si O₂ substrate,ferromagnetic film stack with different thicknesses of Ta/CoFe B/Mg O/Ta were prepared.Through electrical transport measurement and magneto-optical kerr microscopy,the motion law of the magnetic domain wall under the action of external magnetic field and spin orbit torque was studied.（2）The film stack consisting of Ta（5nm）/GdFeCo（4 nm）/Mg O（2 nm）/Ta（2nm）layers was deposited by magnetron sputtering on a thermally oxide Si–Si O₂substrate,with the base pressure lower than 5×10^-8 Torr,where the ferrimagnetic GdFeCowas prepared by the co-sputtering process of Gd and CoFe targets,and the currentinduced magnetization switching in the ferrimagnetic Ta/GdFeCo/Mg O system was studied.The results show that SOT-induced magnetization switching can be achieved at a magnetically compensated temperature point of about 70 K,with almost zero magnetization and a coercive force of nearly 3 T.The SOT efficiency and temperature dependence were quantified by the second harmonic method,and it was found that the enhanced SOT efficiency near the magnetically compensated temperature point was attributed to the negative exchange coupling between the two sets of sublattices of CoFe and Gd.It is proved that SOT switching of near-compensation point ferrimagnetism has great potential for future applications of zero-field switching and ultrafast ferrimagnetism.（3）Crystals with van der Waals layered structure sintered in a single crystalfurnace are selected,and the crystals are mechanically stripped by traditional dissociation methods.The thickness of the thin layer was measured by AFM,and the Laman performance of the laminar peel sample was tested,and finally transferred in a transfer table under vacuum,built into a heterojunction,and tested for transport properties.