Change of Electronic Structure and Magnetic Properties with MgO and Fe Thicknesses in Fe/MgO/Fe Magnetic Tunnel Junction

The effects of the thickness of MgO and Fe on the electronic structure and magnetic properties of Fe/MgO/Fe magnetic tunnel junction was studied using the first principle method. Two series of models with MgO of different thicknesses: Fe(3)MgO(t)Fe(3) (t=1,3,5,7) and with Fe of varied thicknesses: Fe(t)MgO(3)Fe(t) (t=3,4,5,6,7) were established. Calculated results show that in all the models the magnetic moment of Fe increases at the Fe/MgO interface and surface as compared with that of the inner layers. The mag-netic moment of each Fe layer was found to be independent of MgO thicknesses, while the spin-polarization of Fe layer at the interface shows a slight change in function of the MgO thicknesses. The tunneling magnetoresistance (TMR) ratio estimated by the Julliere model has the same change tendency as the spin-polarization has, and the largest value is obtained at the MgO thickness of 5 atomic layers. When the Fe thickness increases, the spin-polarization of interface Fe layer follows up an increase with a decrease. The highest TMR value is achieved when the Fe thickness is of 4 atomic layers.     

Fracture Behavior of TiNi Based Shape Memory Alloy Cold-rolled Tube

The microstructures and interfacial characteristics of matrices at the inwalls and the out-walls of the cold-rolled tube with different amounts of deformation were investigated by the scanning electronic microscope (SEM), the optical microscope (OM), and the trans-mission electronic microscope (TEM) techniques. It was observed that as the amount of deformation increases, the flaws nucleate at the out-walls of the cold rolled tube, the stress-induced martensites change from (111 ) type Ⅰ twins to (011) type Ⅱ twins and then to (100) compound twins, nanocrystals and bulk amorphisation happen, the high density dislocation causes stress concentration at the out-walls of the Ti50Ni50 cold-rolled tube, and then precipitates its fracture, and the Ti2Ni particles strengthen the grain boundaries and curb the dislocation movements during plastic deformation. The inhomogeneity level of the grains in the Ti50Ni50 alloy plays an important role on the fracture of the Ti50Ni50 cold rolled tube.     

英语习语中的饮食民俗文化

英语饮食习语积淀了深厚的民族文化特色,充分认识英语国家的饮食习惯,研究英语习语的来源和饮食民俗文化,有助于我们体会其深层含义.论文分析了英语国家的日常饮食习惯与节日饮食文化,说明了探讨英语饮食习语的学习,必须从其饮食文化方面入手.     

试论公司治理结构下的内部审计

现代内部审计是公司治理结构下新型的内部审计关系,对于实现组织增加价值和提高组织的运作效率具有非常重要的意义和作用.文章分析了审计委托者、审计主体、审计客体三者之间最基本的审计关系,分析三者之间可能存在的矛盾和冲突,提出了解决的办法.