Magnetization Dynamics In Magnetic Nanostructures

Magnetic materials are an important media in the field of data storage.It is closely related to people’s daily lives.Therefore,the study of magnetization dynamics in magnetic nanostructures is a very important issue,in which magnetization reversal of nanoparticle and magnetic domain wall motion have been widely studied in the past few decades.We investigated the magnetic dynamics of the multi-body magnetic particle systems and domain walls by the Landau-Lifshitz-Gilbert equation.The results may have a reference value for future industrial applications of information storage.The first chapter is the introduction,which mainly introduces the popular discipline of spintronics and its application and development in the information storage,and several kinds of carrier forms of magnetic memory devices.The second chapter gives the theoretical basis of this thesis,including several important forms of energy in ferromagnetic materials,the theory of magnetic dynamics.In addition,we also briefly describes several micro-magnetic simulation methods.After the third chapter is the main working part of this thesis.We studied the magnetization reversal of two-body Stoner particles driven by injecting a spin-polarized current through a spin-valve like structure.The results show that the critical switching current(or its density)with dipole-dipole interaction(DDI)can be greatly reduced.In addition,we also conducted a numerical study of the reversal time of the two-body Stoner particle system in the presence of DDI.The forth chapter introduces the magnetization reversal of the multi-body Stoner particle system driven by the transverse magnetic field in a Co material under non-synchronous motion mode.The effects of dipole-dipole interaction on the magnetization reversal of two typical geometrical configurations are investigated.Theresults show that a critical synchronized switching field exists in parallel configuration,beyond which the magnetization vectors of two particles will synchronize to a precession state.Moreover,the critical synchronized switching field diminishes with the DDI strength increases until it ceases to exist.The fifth chapter is also based on the LLG equation.In this chapter,we numerically simulate the motion of domain walls driven by an elliptically polarized magnetic field and a two-frequency polarized magnetic field.The relations between the domain wall(DW)velocity and microwave frequency in a uniaxial YIG ferromagnetic nanowire are investigated.The results show that the DW oscillation frequency is equal to microwave frequency.Moreover,the DW reaches its maximum velocity when the microwave frequency is equal to the ferromagnetic resonance frequency.The sixth chapter is a summary of this thesis.We put forward some problems needed to be solved in future and an outlook about related researches.