Research Of Low Magnetic Damping And High Spin Hall Angle In Ferromagnetic/Non-magnetic Thin Film

The development of next-generation high-performance,low-energy spintronics devices poses an urgent need for material systems with both low magnetic damping and high spin Hall angles.With this background,this thesis focuses on the magnetic damping factor and spin Hall angle of multilayer systems,and explores the mechanisms of different compositions and structures on the material properties,distinguishes the contribution of different mechanisms and the relationship between them,achieves both low magnetic damping and high spin Hall angle,significantly improves the interfacial spin transparency and critical switching current density of the material,and provides new insights for the design of spintronics devices.This has provided new insights into the design of spintronics devices.The main results obtained are as follows:（1）We report the giant spin current generation in CoFeB/Cu_1-xTb_x heterostrucuture thin film arising from the spin Hall effect.The maximum spin Hall angle from our Cu Tb-based magnetic heterostructures was found to be-0.35±0.02 for Cu_0.39Tb_0.61.We find that the contribution of skew scattering is larger than the side jump for lower Tb concentrations（<14.9%）,while the opposite is true for higher Tb concentrations.Additionally,we also studied the Gilbert damping parameter,spin diffusion length,and spin-mixing conductance.According to the temperature dependence of damping,the dominant mechanism of the magnetic damping factor with different Tb content is distinguished and well explained.（2）We report on the enhancement of effective spin Hall angle from the CoFeB/Pt interface by introducing nitrogen into the Pt thin film.Spin-torque ferromagnetic resonance measurements reveal a non-monotonic variation of effective spin Hall angle as a function of the amount of nitrogen gas introduced,i.e.,Q in the film deposition,and the maximumθ_SH=0.16 is obtained when Q is 8%.Our analysis shows that theθ_SH enhancement is mainly attributed to the increase of spin-dependent scattering at the interface.The effective magnetic damping decreases with increasing Q due to the reduced spin orbit coupling.The interfacial spin transparency is also observed to be improved after the introduction of nitrogen.（3）We report the effects of spin Hall effect and effective magnetic damping factor of CoFeB/Pt Ta heterostrucuture thin film.The weakening of the spin-orbit coupling leads to a decrease in the effective magnetic damping factor with increasing Ta concentration.The spin Hall angle first increases then decreases with the doping of Ta,reaching its maximum value V_S/V_A=2.3 at x=0.2.We attribute this non-monotonic variation to the interaction between the contribution of the extrinsic skew scattering mechanism and the spin-orbit coupling.The high-temperature ST-FMR measurement confirm the influence of Ta dpoing on the spin Hall effect and magnetic damping mechanism.Moreover,the decrease of spin mixing conductance and the increase of spin diffusion length lead to the decrease of interface spin transparency.（4）We report the influence of ultrathin Ti insertion layer on the effective magnetic damping and effective spin Hall angle in Co/[Pt/Ti]_n/Pt structure via spin torque ferromagnetic resonance measurements.The effective magnetic damping first decreases with higher number of insertion layer n,reaching its minimum value 0.0079 at n=5.Further increasing n,the attenuation of the spin currents leads to increased damping.We find the bottom Pt layer play the dominant role to extrinsic magnetic damping contribution.The effective spin Hall angle first increase then decrease with the increasing n,with the minimum value 0.21 at n=5.It can be explained as being due to a competition between the increased longitudinal resistivity due to the strong interfacial scattering and the reduced effective spin Hall conductivity originates from the shortening of the carrier lifetime.