Research On Magnetic Moment Reversal In Magneitc Tunnel Junction With Perpendicular Aninsotropy

With the development of information technology and the increasing demand for storage technology,researches on new type of storage device naturally become a hot topic in the current research.How to develop a storage device that is fast,efficient,large capacity,and easy to carry,requires a strong theory as the foundation.Since the end of last century researchers have theoretically predicted that the spin transfer torque(STT)effect can achieve the storage of information under the current driven and the effect becomes the theoretical support for the spin transfer torque random memory(STT-MRAM)research.The core of STT-MRAM is the magnetic tunnel junction(MTJ),which is generally composed of pinned ferromagnetic layer/non-magnetic layer/free ferromagnetic layer.The switching characteristic of the magnetization in the free layer can directly reveal the performance of the storage device.In this paper,the precession and switching trajectory of magnetization are numerically stimulated in the free layer of MTJ through the theoretical model based on the Landau-Lifshitz-Gilbert-Slonczewski(LLGS)equation.Besides the STT effect,other factors affecting the precession of magnetization are also being discussed.Based on the trilayer nanopillar structure and its theory of MTJ,thepentalayer nanopillar device is proposed,and the main content of this paper is as follows:First,this paper introduces the development history,research significance and application prospect of magnetic storage technology.The theory of magnetic storage device in spintronics is briefly described.Second,this paper disscusses basic theories in ferromagnetics,mainly from the origin of magnetism,the diamagnetism and paramagnetism of materials,and the basic characteristics of ferromagnetic materials.Meanwhile,the uniform precession of ferromagnetic substance under constant field is described.Third,applying macrospin model and LLGS equation,the dependence of the magnetization switched on the thickness of the free layer is investigated,respectively,in the spin-valve(SV)and MTJ with particular magnetization and the effect of the field-like field on the swithching of the magnetization is also discussed.The results show that both the thickness of the free layer and the field-like field can directly affect the swithching speed of the magnetization.Fourth,on the basis of above researches on the perpendicular MTJ,the other relevant effects are introduced to improve the swithching speed of the magnetization.In this part,the researcher mainly discusses the Anomalous Hall Effect(AME)assisted on STT effect.The research shows that,the Anomalous Hall assisted can effectively reduce the critical current of the magnetization swithched in the free layer increasing the magnetization speed from position "-1" to position "0",so it can improve the swithching of magnetization.In addition,the influence of Rashba effect on the magnetization swithched is briefly introduced.Fifth,this paper proposes the pentalayar nanopillar device on the foundation of the trilayar nanopiller device.By comparing two types of the device above with the perpendicular magnetization,the contrasted figures are given about the trajectory of the magnetization precession and the swithching time of the magnetization.Subsequently,two kinds of biasing configuration are proposed in the pentalayarnanopillar device with the in-plane magnetization,one of which is the pinned layer biasing configuration and the other of which is the free layer biasing configuration.The effect of biasing configuration on magnetization swithched is discussed.The results show that,in contrasted with the trilayar nanopiller device,the pentalayar nanopillar device with the perpendicular magnetization can obviously accelerate the swithching speed of the magnetization.In the pentalayar nanopillar device with in-plane magnetization,both pinned layer biasing configuration and the free layer biasing configuration can reduce the swithching time of the magnetization and this effect of the free layer biasing configuration is more significant.