The Study Of Spin Pumping Effect In YIG/normal Metal Heterostructures

Spin current is the directional transport of spin angular momentum in material.It is not only the core DOF(degree of freedom)of new physical effects in spintronics,but also the core carrier to design a new generation of high-density,high-speed,low-power magnetic storage and to realize the reversal of local spin(or magnetic moment)in processing devices.Understanding the physical properties of the spin current and the microscopic mechanism of the interaction between the spin current and the material is the key scientific problems in comprehending the coupling between spin,charge,and orbit.In this thesis.the spin pumping effect in yttrium iron garnet /metal(YIG/NM)heterogeneous is employed to study the physical characteristics of pure spin current,the effective spin mixing conductance(characterize the injective efficiency of pure spin current)and the spin Hall Angle(characterize the conversion efficiency between spin and charge currents).The main innovative conclusions are as follows: 1,We proposed a method to obtain pure spin pumping signal,and established the spatial symmetry of spin pumping.To refrain the issue that both spin rectification signal and spin pumping signal may exist in the FM/NM system,we proposed to utilize YIG/NM system to measure pure spin pumping signal.It is found that the angular dependence of spin pumping and spin rectification signal is obviously different,when the magnetization rotates in the xy,yz,xz plane.Meanwhile,a non-uniform spin pumping signal with the cos3? angular dependencies was found.Therefore,the accurate measurement of spin pumping signal should be performed at ?=90o or between the Hall electrodes,after excluding the contribution of spin rectification by using the spatial symmetry.2,We realized the precise characterization of the spin Hall angle of the PtxPd1-x(0 ?x ?1)alloy,and found its main microscopic mechanism.By calibrating the spin diffusion length,the effective mixing conductivity and microwave field magnitude,the spin Hall angle of PtxPd1-x alloy was accurately determined by the spin pumping signal of YIG/ Ptx Pd1-x measured under ?=90o geometry(Pt=0.125 0.015SH? ±).The scaling relation between spin Hall angle and charge conductance reveales that the skew scattering is the main microscopic mechanisms of spin relative scattering in Ptx Pd1-x.3,We studied the relationship between effective spin mixing conductance and the resonance of magnetization,and realized the effective control of effective spin mixing conductance.It is found that the amplitude of spin pumping signal increases linearly with sin2?c((8(8 is the precession angle)in both linear and nonlinear magnetization resonance region,which indicates that the effective mixing spin conductivity is an intrinsic parameter and is independent with the resonance mode or the resonance linewidth.The change of the effective spin mixing conductance with x in the YIG/PtxPd1-x system reveals that spin-orbit coupling is the regulation mechanism of effective spin mixing conductance in the alloy.At the same time,the discovery of the out of plane anisotropy of the effective spin mixing conductance indicates that the effective spin mixing conductance can be re-regulation by change the spin polarization direction.4,We measured the ac spin pumping signal quantitatively,and realized the regulation of magnetic anisotropy field and resonance damping by utilizing electric field.By using the spin torque and spin rectification effect,both ac and dc spin current generated by spin pumping effect were measured in YIG/FeNi heterojunction.We separated the two signals by using spatial symmetry,which show that the ac spin current is 71 times larger than the dc spin current.The magnetic properties of PMN-PT/Co was systematically studied by using spin rectification effect.We found that the magnetic anisotropy field and the resonance damping of Co change with the polarization history of PMN-PT,which indicates that the electric field can be used to control the spin pumping effect.