| With the discovery and application of physical effects such as giant magnetoresistance effect and spin moment effect by researchers,spintronics has been developed rapidly in recent decades,and those spintronic devices developed on the basis of spin transfer moment(STT)and spin-orbit moment(SOT)theory in the market have been widely welcomed by consumers.The performance of these electronic devices is largely influenced by the ferromagnets and antiferromagnets,which are the basic components of spintronics devices.In ferromagnets and antiferromagnets,we can classify the magnetization direction as common-linear and non-common-linear,where the magnetization direction is called common-linear,while the magnetic moments of magnetic atoms in ferromagnets and antiferromagnets are not necessarily along the same magnetization direction,which is generally called non-common-linear.This magnetic sequence has led to a number of new physical discoveries for researchers,such as magnetization resistance frustration.It has been found that the transition metal oxide layer on the ferromagnetic/insulator/ferromagnetic surface of ferromagnetic tunnel junctions is often in a non-common-line magnetic order,but there is still a large gap in the electron transport properties under non-common-line magnetic order compared to common-line magnetic order.In view of the theoretical gap and the great application potential,this paper will combine density generalization and nonequilibrium Green’s function to study and analyze the energy band,density of states and electron transport properties of several types of noncommon-linear magnetic order systems,such as Mn O,Ni O,Co O,gold atomic chains,8ZGNR graphene and Fe/Mg O/Fe magnetic tunnel junctions.The main work includes the following aspects:(1)Chapter 1,which gives a brief description of the research process and background of spintronics,as well as the principles related to co-linear and non-co-linear magnetic sequences.(2)Chapter 2 introduces the first nature principle,the density generalization/non-equilibrium Green’s function method and its difference between the common-linear and non-common-linear magnetic sequence systems,and briefly describes the Open Mx and Material Studio software used.(3)In Chapter 3,Material Studio is used to construct the structures of Mn O,Ni O and Co O,and Open Mx is used to calculate the energy bands and density of states for each of the three non-commonlinear magnetic order metal compounds,and the energy bands and density of states of the three compounds are analyzed and compared at the end of the run.The simple metal oxides are borrowed to introduce the subsequent study of graphene and more complex magnetic tunnel junctions under non-common-linear magnetic order conditions.(4)In Chapter 4,the electron transport properties of Fe/Mg O/Fe tunneling junctions are calculated using Open Mx to investigate the electron transport-related properties of magnetic tunneling junctions such as conductivity,current and tunneling rate TMR.(5)Chapter 5.(5)In Chapter 5,Open Mx is used to simulate gold atomic chains and 8ZGNR graphene,and nitrogen atoms are doped on the surface of graphene to analyze whether the transport properties of graphene change under doped and undoped conditions.The experimental results reveal that the bound states produced by the doped impurities form a backscattering effect on the electrons in transport,reducing the transmission coefficient and increasing the tunneling magnetoresistance more significantly.(6)In Chapter 6,the energy bands and density of states of Hurst alloys are studied with Co2 Fe Al and Co2 Cr Al and the magnetic tunneling heterojunction is constructed,and the transport properties are simulated and calculated to study the effect of U on their properties.The experimental results reveal that typical semimetallic properties are found in both Co2 Fe Al and Co2 Cr Al,and both Hessler alloys exhibit a mixture of conducting and semiconducting states,while GGA+U has certain superiority over GGA.The conductivity and tunneling rates of Co2 Fe Al and Co2 Cr Al were obtained by studying the transport properties,and the structure of the Hessler alloys was optimized based on the results of the study,and the magnetic tunneling heterojunction TMR reached 200000%,which is an important finding to be verified by experiments.(7)Chapter 7,summarizes and outlooks the research work of this paper on non-common-linear magnetic sequential systems... |
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