Investigation On Perpendicular Anisotropy In MgO/CoFeB/Ta Multilayers And The Preparation Of Ferrimagnetic Insulators

It is well known that the electron has another intrinsic degree of freedom besides the charge:spin.So,in addition to the use of electron charges,the spin properties of electrons can also be used to store and process information.Then a new research field in condensed matter physics,spin electronics,had be found.With the development of spintronics,the generation,injection and detection technology of the spin currents has been gradually mastered at the same time,a variety of spin electronic devices which work based on spin current have been playing a huge role in our daily life.Since the twentieth Century,the development of science and technology has been growing faster and faster,and a variety of high-tech electronic devices have emerged,and the speed of updating is becoming more and more rapid.In order to meet the needs of people,in order to improve the density of information storage and the speed of reading and writing,the research of magnetoresistance is induced our interest.Because of the advantages of small working magnetic field,high sensitivity and low saturation magnetic field,the magnetic tunnel junction with vertical magnetic anisotropy can play its advantages in some spintronic devices,such as magnetic sensor,TMR head and magnetic random access memory(MRAM),so scientists have received the attention of scientists.CoFeB is an important material for preparing magnetic tunnel junctions with perpendicular magnetic anisotropy.Therefore,it is crucial to study the vertical anisotropy of CoFeB thin films.One of the work of this thesis is to prepare the CoFeB thin film with PMA,explore the MgO/CoFeB/Ta three layer film,and the influence of the thickness,sputtering power and annealing temperature on the vertical magnetic anisotropy of the optimized multilayer film structure(Ta/MgO/CoFeB/Ta/MgO).The anomalous Holzer effect(AHE)is used to characterize the perpendicular magnetic anisotropy of the films.Through the experiments,for the films deposited at 0.2 Pa and the sputtering pressure of CoFeB is in the 10w to about 15w,the MgO\CoFeB\Ta thin films show good perpendicular magnetic anisotropy with CoFeB layer thickness varying between 0.80～1.0 nm,which the Ta layer thickness modification takes little effect.To optimize the structure of films,the CoFeB thickness range becomes larger which could make the films show perpendicular magnetic anisotropy.And the change of MgO layer thickness within the range of 0.6～3nm has obvious effects on perpendicular anisotropy of the films.The thickness of the MgO layer is fatal to the formation of films with perpendicular magnetic anisotropy.Furthermore,proper annealing can improve the PMA of MgO\CoFeB\Ta films.Recently,with the rapid development of spintronics,the ferromagnetic insulation material with small ferromagnetic resonance line width and low Gilbert damping coefficient has became an important part of spintronics,which has been implemented widely in Spin Hall Magnetoresistance(SMR).Inverse Spin Hall Effect(ISHE),Spin Seebeck Effect(SSE)and so on.TmIG and LuIG have received great attention due to their excellent magnetic properties.So another important work in this paper is the sintering of TmIG and LuIG sputtering targets.Different from the traditional solid-phase reaction,we used the fusion nitric acid to sintering the TmIG and LuIG targets.2-inch high purity targets with the saturation magnetization of 15.40 emu/g and 16.97emu/g were sintered successfully,in which theXRD peak show that the targets component are TmIG and LuIG polycrystalline.Our new sintering method sheds light on the preparation of high purity nano crystal thin film.