Investigate Of Magnetic Anisotropy And Spin Pumping Effect In Ferromagnetic Multilayer Film

Spintronics,an emerging discipline,involves the study of active control and manipulation of spin degrees of freedom in solid-state systems.Campared with traditional electronic devices,the spintronic devices have attracted much attention because of their low energy consumption,high integration and non-volatility.Magnetic random access memory(MRAM)is one of the main devices.At present,magnetic random memory can be divided into two kinds.One is STT-MRAM based on spin transfer torque,and STT-MRAM with perpendicular magnetic anisotropy is a hot research topic.Therefore,in the first part of this paper,the variation of perpendicular magnetic anisotropy with the number of periods in the magnetic multilayer system is studied.Meanwhile,the synthetic antiferromagnet is prepared based on the multilayer system.The variation of interlayer exchange coupling strength with the thickness of non-magnetic spacer layers is studied.Then,the generation,transport and transformation of spin current are important factors that determine the performance of SOT-MRAM.the second part of this paper studies the spin pumping effect in magnetic metal and heavy metal multilayer.By changing the oxygen concentration in heavy metals and the oxidation of the interface,The effects of oxidation on spin pumping efficiency and spin mixing conductance were investigated.The research work is divided into the following aspects.In the first part,two kinds of multilayer systems with perpendicular anisotropy,Co/Ni and Co/Pt,were selected to study their perpendicular magnetic anisotropy by changing the period number n=2,4,6,8,10.It is found that the perpendicular anisotropy of[Co/Ni]₄is the most significant in the Co/Ni system.When the number of periods is greater than 4,the perpendicular anisotropy decreases with the increase of the number of periods.When the number of periods reaches 8,10 layers,the easy axis of the film shifts into the plane.Whereas the perpendicular anisotropy of Co/Pt increased with the increase of the number of periods,with the maximum value of4.7k G at n=10.The[Co/Ni]₄and[Co/Pt]₆structures with the largest coercive field in the system were inserted into Cu and Ru spacer to form the synthetic antiferromagnet,respectively.The results show that the exchange coupling strength between Co/Cu/Co layers is weaker than that of Co/Ru/Co layers.As the thickness of Ru is 0.9nm,the antiferromagnetic coupling strength-J_IECis the largest,reaching2.7erg/cm²,and the oscillation period is 1.16nm.In the second part,The magnetic properties of Py thin film has been characterized by FMR,the damping factor of Py film is 0.01192,and the effective magnetization4?M_effof Py film is 9.912 k G.Subsequently,a set of Ta O_xthin film with oxygen flow ratio Q=0-0.5%are prepared,corresponding to the oxygen concentration n=0-9.64%,and the resistivity increases with the increase of oxygen flow Q.After the thin films are characterized,Ta O_x/Py strips with a length of 6 mm and a width of 200 um are prepared for the Spin Pumping-Inverse Spin Hall Effect measurement.By fitting damping factors,it is found that Ta O_x/Py system has considerable spin mixing conductivity,which varies from 22.85 nm^-2to 35.54 nm^-2.In the sample with oxygen flow ratio Q=0.3%,the spin Hall Angle of Ta increases by 1.7 times.Meanwhile,compared with Py/Ta interface,the oxidized Py(O)/Ta interface has better spin transmittance and reduces the spin memory loss in devices.