Spin-Dependent Transport in Magnetic Tunnel Junctions

磁隧道结中的自旋相关输运

• 批准号: 0076171
• 负责人: Shufeng Zhang
• 金额: $ 15万
• 依托单位: University of Missouri-Columbia
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0076171&HistoricalAwards=false
• 关键词: Spin; Dependent; Transport; Magnetic; Tunnel

This grant supports theoretical research to explore fundamental physics of spin-polarized transport properties in magnetic tunnel junctions. There are two focused areas to the research: to establish and generalize new aspects of tunneling mechanisms and tunneling formulations involving magnetic electrodes, and to investigate the influence of external defects on the I-V characteristics of realistic tunnel junctions. This research will facilitate the development of novel spin electronics, which merge spin degrees of freedom into high technologies.In the first part of the research, earlier theoretical formulations will be extended by including the spin-polarized nature of tunneling. Such an extension is not as simple as adding two independent spin channels in a trivial manner. Rather the formulations of spin-polarized tunneling differ from those of charge tunneling in a significant way. The fundamental new features to be addressed include the local spin current variation near interfaces, spin-dependent electric field penetrations into magnetic electrodes, local versus itinerant states near the interfaces, and critical length scales involving the polarized tunneling. Intrinsic electronic relaxations of charge and spin, which determines the temperature dependence of the spin-polarized tunneling of an ideal junction, will also be investigated. A model system with known electronic stuctures from ab initio calculations will be used to test the validity of the theoretical formulations for spin-polarized tunneling.In the second part of the research, applications will be made of these formulations to various realistic magnetic tunnel junctions. The main emphasis will be on predicting novel features of magneto-transport properties and on interpreting the experimental I-V characteristics. The presence of defects in experimental tunnel junctions leads to quite different I-V characteristics and magntoresistance compared to ideal junctions. Suitable Hamiltonians will be developed to model these defects. The magnetotransport properties will be deduced from these model Hamiltonians by using quantum transport equations. In most cases, appropriate perturbation methods will be first used to simplify the problem so that standard numerical techniques can be used to derive the physical quantities up to the point where detailed comparison with experiments can be made.%%%This grant supports theoretical research to explore fundamental physics of spin-polarized transport properties in magnetic tunnel junctions. There are two focused areas to the research: to establish and generalize new aspects of tunneling mechanisms and tunneling formulations involving magnetic electrodes, and to investigate the influence of external defects on the I-V characteristics of realistic tunnel junctions. This research will facilitate the development of novel spin electronics, i.e., "spintronics," which merge spin degrees of freedom into high technologies.***

该补助金支持理论研究，以探索磁性隧道结中自旋极化输运特性的基础物理。 有两个重点领域的研究：建立和推广新的方面的隧道机制和隧道制剂涉及磁性电极，并调查外部缺陷的影响，对现实的隧道结的I-V特性。 这项研究将促进新型自旋电子学的发展，将自旋自由度融入高科技。在研究的第一部分，早期的理论公式将通过包括隧穿的自旋极化性质来扩展。 这样的扩展并不像以平凡的方式添加两个独立的自旋通道那样简单。 相反，自旋极化隧穿的公式与电荷隧穿的公式有很大的不同。 要解决的基本新功能包括本地的自旋电流变化界面附近，自旋相关的电场渗透到磁电极，本地与巡回状态界面附近，和临界长度尺度涉及的极化隧道。 本征电子弛豫的电荷和自旋，这决定了一个理想的结的自旋极化隧穿的温度依赖性，也将被调查。 在第二部分研究中，我们将利用一个由从头计算得到的具有已知电子结构的模型系统来检验自旋极化隧穿理论公式的有效性，并将这些公式应用于各种实际的磁性隧道结。 主要的重点将是预测新功能的磁输运性质和解释实验的I-V特性。 实验隧道结中缺陷的存在导致了与理想结完全不同的I-V特性和磁阻。 合适的哈密顿将开发这些缺陷的模型。 利用量子输运方程，从这些模型哈密顿量推导出磁输运性质。 在大多数情况下，将首先使用适当的摄动方法来简化问题，以便可以使用标准的数值技术来推导物理量，直到可以与实验进行详细比较的程度。该补助金支持理论研究，以探索磁性隧道结中自旋极化输运特性的基础物理。 有两个重点领域的研究：建立和推广新的方面的隧道机制和隧道制剂涉及磁性电极，并调查外部缺陷的影响，对现实的隧道结的I-V特性。 这项研究将促进新型自旋电子学的发展，即，“自旋电子学”，将自旋自由度融入高科技。