Study On Spin Transfer Torque In Spin Valve

Spin transfer torque is another important discovery of spin electronics after giant magnetoresistance.Based on this effect,it can realize the control of local magnetic moment or spin direction with electric current,which is the core technology of a new generation efficiency,low power consumption,nonvolatile magnetic memory based on the principle of spin electronics.Therefore,it is the frontier problem of spin electronics to achieve man-made control and to master the physical characteristics of spin transfer moments in magnetic and nonmagnetic heterogeneous or multilayer structures.Therefore,this paper takes the classical spin valve multilayer structure as the research object,we obtained physical characteristics of spin transfer torque in such a structure,through studying spatial relations and line shape of spin rectification strength result from anisotropic magnetoresistance and giant magnetoresistance driven by the microwave magnetic field and the spin transfer torque in the spin valve,the main conclusions are as follows:1.The spin rectification theory of spin valve structure is established.Based on the classical spin rectification theory,the variation law of the rectification strength and the symmetry line shape of the resonant peak in the spin valve are obtained,which are induced by the giant resistance and the anisotropic magnetoresistance coupling of the microwave magnetic field and the spin transfer torque.Where the resonant is an antisymmetric line shape driven by the microwave magnetic field,and the resonant is also an antisymmetric line shape driven by the vertical component of spin transfer torque,while the resonant is symmetrical line shape driven by parallel component.2.Based on the spatial symmetry of various effects,the dynamic characteristics caused by the spin transfer torque are obtained.It is found that the relative angle of magnetization of two magnetic layers in spin valve is an important factor to determine the strength of spin transfer torque.The spin rectification mechanism is dominated by the coupling of anisotropic magnetoresistance and microwave magnetic field in high field condition,while it is dominated by the coupling of giant magnetoresistance and spin transfer torque in low field condition.And in the case of in-plane magnetization,the vertical component of the spin transfer torque dominates in spin valve.In a vertical magnetized spin valve,the contribution of the parallel component of the spin transfer torque is found.The relative strength of the two moments can be man-made by controlling the relative angle of the magnetization.