Study On Preparation And Interfacial Perpendicular Magnetic Properties Of Pd/Co Multilayers And Heusler Alloy Thin Films

With the development of nano-scale materials,the perpendicular magnetic properties of the interface,which are closely related to size and dimension have been the hotspots in the field of magnetism.Among them,the nano-heterojunction structure composed of ferromagnetic and non-magnetic metal or oxide interfaces has the advantages of high thermal stability,strong perpendicular magnetic anisotropy,and easy to be compatible with the semiconductor process.Pd/Co multilayer films have great potential to be integrated with CMOS technology to fabricate new generation magnetoelectric logic devices.However,Pd/Co multilayer films with perpendicular magnetic anisotropy are usually thin in thickness and low in effective spin polarization,which affects their applications in the field of spintronics.Therefore,designing Pd/Co multilayer films with excellent performance is very important for its application in magnetoelectric devices.Theoretically,Heusler alloy with 100%spin polarizability is a new type of magnetic material that has attracted much attention in the field of spintronics.Co₂FeAl_0.5Si_0.5?CFAS?alloy film has large saturation magnetization,low damping factor,and high thermal stability,which has a wide application prospect in the spin electronic device,but related system research is still rare.In this thesis,the preparation process and magnetic,optical and electrical properties of two kinds of perpendicular magnetic anisotropy films,Pd/Co multilayer films and CFAS thin films,have been systematically studied.The main contents are as follows:Firstly,Pd/Co multilayer films with perpendicular magnetic anisotropy were prepared by magnetron sputtering.The effect of the thickness of the magnetic layer on the magnetic properties of multilayer films was studied.The results show that the perpendicular magnetic anisotropy can be obtained only when the thickness of the magnetic layer is lower than 1nm.The structure of Pd/Co multilayer film was optimized by inserting a MgO layer.The results show that the perpendicular magnetic properties of multilayer films can be maintained in the range of magnetic layer thickness?1-5 nm?after annealing at 350?.Secondly,in the study of the effect of the thickness of MgO layer on the perpendicular magnetic properties of the multilayer films,it was found that the multilayer films show perpendicular magnetic anisotropy when the thickness of the Co layer is larger than that of 1nm after annealing at 350?even if the MgO layer is not inserted into the Co layer.In the study of the effect of interface effect on the perpendicular magnetic anisotropy of multilayer films,it is observed that the upper and lower interfaces of Pd/Co have different effects on the vertical magnetic anisotropy of multilayer films.In the study of the effect of annealing temperature on the magnetic properties of the multilayer films,it was found that the coercive force of the films increases with the increase of the annealing temperature.when the annealing temperature is higher than 400°C,the variation of the rectangular degree of the hysteresis loop may be related to the diffusion of atoms at the interface caused by the excessive annealing temperature.Thirdly,the effect of the magnetic layer and Pd,MgO layer thickness on perpendicular magnetic anisotropy of CFAS alloy film is studied by using magneto-optical Kerr effect.It was found that only when the thickness of the magnetic layer was lower than 4.5 nm,the multilayer film system had perpendicular magnetic anisotropy,which was attributed to the competition between the perpendicular magnetic properties of the interface and the demagnetization in the system.In addition,it was found that both the Pd/CFAS and CFAS/MgO interfaces have a positive contribution to the perpendicular magnetic anisotropy of the thin films.Finally,the double CFAS thin films with MgO as the isolation layer were successfully prepared.The continuous flipping of CFAS layers with different thickness under different external fields was observed,and the lower the test temperature,the larger the magnetic field interval between the two flip-ups.