Interface Effects in Magnetic Tunneling Junctions

这个个人研究者奖是颁给特拉华大学的一位年轻教授，他的项目研究了电极-绝缘体界面如何影响自旋依赖的电子隧穿和磁隧道结的磁性。这些系统是新一代高磁阻器件的有希望的候选者，并有助于推进我们对自旋输运的理解。重要的问题，如隧道磁电阻对温度和偏置电压的强烈依赖性，归因于界面自旋，但仍未解决。提出了一系列的电输运和结构研究，以将界面特征与自旋相关的输运性质联系起来，并测试已经开发的竞争理论。这项工作的一个重要特点是使用具有楔形铝金属层的样品。这样就可以很容易地获得具有欠氧化、完全氧化和过度氧化的隧道屏障的连接。要研究的现象包括：电极-绝缘体界面的电荷和磁化积累，磁电极中自旋相关的电场分布，以及由于电子-电子相互作用导致的自旋向上和自旋向下的电子带之间的化学势分裂。所提出的研究与半导体研究有关，涉及门控介电材料，混合铁磁-半导体异质结构，以及半导体或金属的自旋注入。参与该项目的研究生将接受物理学、纳米结构材料和器件制造方面的培训，这些都是目前科学和技术领域的前沿。这种培训将为他们在工业、政府或学术界的一系列职业生涯做好准备。薄膜磁性多层结构正在推动一种新的电子学方法，这种方法基于载流子的自旋状态（向上或向下），而不是像传统的半导体电子学那样基于其电荷。例如，磁隧道结是新一代磁阻器件和理解自旋输运基本方面的有希望的候选者。在这些系统中，金属和绝缘层之间的界面在决定电气和磁性能方面起着关键作用。该个人研究者奖授予了特拉华大学的一位年轻教授，他的项目包括一系列电气测量和结构研究，旨在将界面结构与自旋相关的输运性质联系起来，这是一个重要的技术问题。将研究电极-绝缘体界面的基本方面，如：界面上的电荷和磁化积累，磁电极中自旋相关的电场分布，以及电子-电子相互作用的作用。所获得的知识预计将有利于涉及混合磁半导体异质结构和自旋注入装置的新研究领域。该项目为学生提供了极好的研究和教育机会，该跨学科项目专注于当前最前沿的科学和技术领域的物理和材料。学生将获得纳米结构材料和器件制造方面的严格培训和技能，为他们在工业、政府或学术界的一系列职业生涯做好准备

This individual investigator award is to a young professor at the University of Delaware for a project that investigates the fundamental aspects of how electrode-insulator interfaces affect spin-dependent electron tunneling and the magnetic properties of magnetic tunnel junctions. These systems are promising candidates for new generations of highly magnetoresistive devices and for advancing our understanding of spin transport. Significant issues, such the strong temperature and bias voltage dependence of the tunneling magnetoresistance, are attributed to the interfacial spins, but remain unresolved. A series of electrical transport and structural investigations are proposed to correlate interface characteristics with spin-dependent transport properties and test competing theories that have been developed. An important feature of this work is using samples with a wedged-shaped aluminum metal layer. This allows junctions with under-, completely-, and over-oxidized tunnel barriers to be readily obtained. Phenomena to be investigated include: charge and magnetization accumulations at the electrode-insulator interfaces, a spin-dependent electric field distribution in the magnetic electrodes, and a chemical potential splitting between spin-up and spin-down electronic bands due to electron-electron interactions. The proposed research has relevance to semiconductor research involving gated dielectric materials, hybrid ferromagnet-semiconductor heterostructures, and spin-injection into semiconductors or metals. Graduate students involved in this project will receive training in physics, nanostructured materials, and device fabrication that is currently at the forefront scientific and technical areas. This training will prepare them for a range of careers in industry, government, or academe. %%%Thin film magnetic multilayer structures are driving a new approach to electronics that is based on the spin state (up or down) of the carriers rather than on its charge as in conventional semiconductor electronics. Magnetic tunnel junctions, for example, are promising candidates for new generations of magnetoresistive devices and for understanding fundamental aspects of spin transport. In these systems, interfaces between metal and insulating layers play a critical role in determining the electrical and magnetic properties. This individual investigator award to a young professor at the University of Delaware is for a project consisting of a series of electrical measurements and structural investigations directed at correlating interface structure with spin-dependent transport properties, a problem of technological importance. Fundamental aspects of electrode-insulator interfaces will be studied such as: charge and magnetization accumulation at the interface, a spin-dependent electric field distribution in the magnetic electrodes, and the role of electron-electron interactions. Knowledge gained is anticipated to benefit new research fields involving hybrid magnetic-semiconductor heterostructures and spin-injection devices. This project offers excellent research and education opportunities for students within an interdisciplinary program focused on physics and materials that is currently at the forefront scientific and technical areas. The students will acquire rigorous training and skills in nanostructured materials and device fabrication that will prepare them for a range of careers in industry, government, or academe.***