Regulation Of Domain/Domain Wall Motion And Skyrmion In Pd-based Ferromagnetic Thin Films By Perpendicular Magnetic Anisotropy

Nowadays,with the advent of the era of 5G and the Internet of Things,more and more high-tech electronic products have entered the world of people,resulting in a convenient,comfortable and interconnected life.However,more and more problems have occorred during the practical application of these electronic products,such as slow reading speed,short life,and high power consumption.So how to better solve these problems is crucial for the development of future information storage and low-power logic devices.With the rapidly development of spintronic basing on the research of topological magnetic materials,the regulation of magnetic domain/domain wall dynamics in magnetic ultra-thin films has become the focus in the scientific research,especially the exploration of new regulation methods for magnetic domains due to its application in future low-power devices.Due to its small size,low current density,and good stability,skyrmion is expected to be an important carrier for the future's high-density and low-energy devices.However,skyrmion still faces many problems in the practical process of devices.For example,there are few materials that can stabilize skyrmion at room temperature,and the stability of skyrmions depends on the existence of external field.Therefore,it is still a research hotspot that how to achieve the stable existence of skyrmion at room temperature and zero field.Focusing on the above issues,this paper takes the regulation of the domain wall dynamics and skyrmions in Pd-based ferromagnetic ultra-thin films by perpendicular magnetic anisoropy as the research topic.[Co/Pd]_n/Py magnetic ultra-thin film systems,Pd/Co/Ru magnetic heterostructure,and Pd/Co/Pd multilayer films were prepared by magnetron sputtering.We use a variety of methods to explore the changes in this thesis,such as ferromagnetic resonance,magnetic domain observation,and micromagnetic simulation.The main research contents are as follows:1.We have investigated the high frequency properties of exchange-coupled[Co/Pd]_n/Py multilayers by changing the number of cycles and the thickness of Py,and we also have studied metastable magnetic bubble in[Co/Pd]₄/Py multilayers.By ferromagnetic resonance analysis,we found that the variation of high frequency performance of[Co/Pd]_n/Py multilayers at different temperatures.The spin reorientation transition?SRT?process in[Co/Pd]₆/Py multilayers was studied using the first-order inversion curve?FORC?,and the magnetic domain phase in the SRT process was obtained through 2D and 3D FORC phase diagrams.The micromagnetic simulation was also used to study the evolution process of metastable magnetic bubble in[Co/Pd]₄/Py multilayers.Our experimental results expand the understanding of high frequency properties in ultrathin exchange-coupled multilayer films and facilitate the development of future fast switching spintronics devices such as magnetic sensors and magnetic random access memory.2.We have investigated the domain wall motion assisted by surface acoustic wave?SAW?in[Co/Pd]₂/Pd?t?/Py multilayers and Pd/Co/Ru heterostructure.The SAW devices were obtained by lithography,ion beam etching and magnetron sputtering.The polar magneto-optic Kerr microscope?MOKE?was used to observe the magnetic domain structure.The experiment results showed the variation of the domain wall motion assisted by surface acoustic wave?SAW?.Our findings can provide a good direction for the investigation of SAW-assisted magnetic domain wall motion,and may have the potential applications in the future SAW-based spintronic devices.3.We have systematically conducted a regulation study on the skyrmion from symmetry and asymmetry by changing the thickness of the Co layer,the Pd layer and the number of cycles in the Pd/Co/Pd material system.In the aspect of symmetry,the MFM results show that the zero-field skyrmion at room temperature can be occurred when the thickness of Co is 0.4 nm and the number of cycles N reach 9 and 12.The micromagnetic simulations well verify the above experimental results.In terms of asymmetry,the L-TEM results show that the evolution process of skyrmion in[Pd/Co/Pd]_n multilayer films.The first-order inversion curve?FORC?diagram was used to analysis the evolution process of skyrmion in[Pd/Co/Pd]_n multilayer films.Our experiment has well explored the generation and variation of zero-field skyrmion at room temperature and the evolution of high density skyrmions,which can be used for reference in the future device application of skyrmions,such as skyrmion-based magnetic random access memory?MRAM?and logic device.