Steady-State and Dynamical Measurements of Spin-Dependent Tunneling via Discrete Quantum States

非技术：所有的电子都带有一个固有的自旋和电荷。因此，通过作用于电子的自旋（一种被称为“自旋电子学”的策略）来控制电子的流动是可能的，而不是使用传统的技术来操纵它们的电荷。本项目将研究影响纳米尺度结构中电子自旋动力学的基本机制，以及导致这些结构中的电子运动依赖于它们的自旋方向的机制。要进行的研究将涉及比较非磁性量子态、少自旋态和全磁性高自旋态的性质，以及自旋如何在这些不同的材料中被激发、进动和放松。这项工作将有助于目前正在进行的开发和优化实用的基于自旋的设备，如磁场传感器（现在用于磁盘驱动器）和非易失性磁随机存取存储器的快速进展。接受该项目的研究生和本科生将获得纳米制造和表征技术方面的广泛专业知识，以及口头和书面表达工作的技能，并为成为纳米技术的未来领导者做好充分准备。技术：本项目将利用纳米尺度样品中量子化能级的电子隧穿测量来研究磁性器件中的自旋输运和自旋态的动力学。通过比较非磁性量子态、少自旋态和全磁性高自旋态的性质，本研究将试图描述影响自旋相关隧道效应、自旋积累和弛豫以及集体磁性作为交换相互作用强度增加的函数的基本机制。该项目不仅将研究稳态电学特性，还将开发实验技术来测量单个纳米级磁铁在响应磁场或电流感应转矩时进行进动和切换的动态特性。这项工作将对优化用作磁盘驱动器传感器的磁隧道结器件和理解正在研究用于非易失性磁随机存取存储器的自旋转移扭矩产生的磁激励具有实际意义。接受该项目的研究生和本科生将获得纳米制造和表征技术方面的广泛专业知识，以及口头和书面表达工作的技能，并为成为纳米技术的未来领导者做好充分准备。

Non-technical:All electrons carry with them an intrinsic spin, as well as electrical charge. It is therefore possible to control the flow of electrons by acting on their spin (a strategy known as "spintronics") rather than by using conventional techniques which manipulate their charge. This project will investigate the fundamental mechanisms which affect the dynamics of electron spins in nanometer-scale structures and which cause the motion of electrons within these structures to depend on their spin orientation. The research to be pursued will involve comparing the properties of non-magnetic quantum states, few-spin states, and fully-magnetic high-spin states, and how spins can be excited, precess, and relax in these different materials. The work will contribute to the rapid progress now underway to develop and optimize practical spin-based devices such as magnetic field sensors (now used in disk drives) and non-volatile magnetic random access memories. The graduate and undergraduate students to be trained on the project will gain broad expertise in nanofabrication and characterization techniques, as well as skills in presenting their work verbally and in writing, and will be well-prepared to be future leaders in nanotechnology.Technical:This project will utilize electron-tunneling measure-ments of quantized energy levels in nanometer-scale samples to study spin transport in magnetic devices and the dynamics of spin states. By comparing the properties of non-magnetic quantum states, few-spin states, and fully-magnetic high-spin states, the work will seek to characterize the fundamental mechanisms affecting spin-dependent tunneling, spin accumulation and relaxation, and the emergence of collective magnetic properties as a function of increasing exchange-interaction strength. The project will investigate not only steady-state electrical properties, but will also develop experimental techniques to measure the dynamical properties of individual nanoscale magnets as they undergo precession and switching in response to magnetic fields or current-induced torques. This work will be of practical relevance for optimizing magnetic tunnel-junction devices used as sensors in disk drives and for understanding magnetic excitations produced by spin-transfer torques which under investigation for use in non-volatile magnetic random access memory. The graduate and undergraduate students to be trained on the project will gain broad expertise in nanofabrication and characterization techniques, as well as skills in presenting their work verbally and in writing, and will be well-prepared to be future leaders in nanotechnology.