Current - Induced Torques in Ferromagnetic and Antiferromagnetic Structures

*非技术摘要*电子是负责金属内部电流的基本粒子，它不仅具有电荷，而且带有本征自旋。在大多数现有的电子设备中，自旋不起任何作用。然而，在过去的十年里，新一代的技术已经开始发展，其中电子自旋被操纵以添加新的功能。这种自旋电子学，或称自旋电子学，已经在硬盘驱动器中以磁场传感器的形式得到了广泛的应用，它还在加紧开发，以制造计算机存储器，其中自旋排列的电流重新定位铁磁元件以存储信息。这项研究项目的目标是对自旋排列的电子与铁磁体或其他选定材料之间的相互作用有新的理解，特别是理解这些相互作用可能产生的电流感生扭矩。该项目将包括开发新的实验技术，以实现对电流感应自旋扭矩的强度和方向的准确测量，并成像铁磁体的磁化如何随着扭矩的变化而移动。这项工作将促进对电子自旋动力学的基本理解，并将提供开发磁存储器和其他技术所需的信息和技术。该项目支持的研究生和本科生也将在纳米科学方面获得优秀的跨学科培训。*技术摘要*本项目的目的是对自旋转移扭矩有新的理解，自旋转移扭矩是自旋极化电流将其自旋角动量转移到铁磁体和(可能)反铁磁体以重新定向其磁矩的机制。已经证明，与使用常规磁场相比，自旋转移可以提供比传统磁场更强的单位电流扭矩，并且自旋扭矩可以有效地驱动磁开关和进动。这项拟议的工作将发明新的实验技术，使定量测量铁磁层中自旋扭矩的强度和方向成为可能。它将推动超快电学测量和时间分辨X射线显微镜技术的发展，以了解自旋力矩可以激发的磁动力学。该项目还将把自旋力矩的研究扩展到新的材料类别，特别是磁性纳米粒子和反铁磁体，对这些材料的有趣效果进行了预测，但尚未进行明确的实验。该项目的影响将是促进对电子自旋动力学的基本理解，并提供开发自旋扭矩驱动的磁存储器、频率可调的纳米级微波源和其他技术所需的信息和实验技术。该项目支持的研究生和本科生还将获得纳米科学方面的优秀跨学科培训。

****NON-TECHNICAL ABSTRACT****Electrons, which are the fundamental particle responsible for electrical currents within metals, possess not only electrical charge but also carry an intrinsic spin. In most existing electrical devices, the spin does not play any role. However, in the past decade new generations of technology have begun development in which the electron spins are manipulated to add new functionalities. This type of spin-electronics, or "spintronics", has already achieved widespread use in the form of magnetic-field sensors in hard disk drives, and it is also under intense development to make computer memories in which spin-aligned electrical currents reorient ferromagnetic components to store information. The goal of this research project is to develop new understanding about the interactions between spin-aligned electrons and a ferromagnet or other selected materials, and particularly to understand current-induced torques that can arise from these interactions. The project will include the development of new experimental techniques to achieve accurate measurements of the strength and direction of current-induced spin torques, and to image how the magnetization of a ferromagnet moves in response to the torque. This work will advance basic understanding of electron spin dynamics and will provide information and techniques that will be needed for the development of magnetic memories and other technologies. The graduate and undergraduate students supported by the project will also gain an excellent interdisciplinary training in nanoscience.****TECHNICAL ABSTRACT****The aim of this project is to develop new understanding about spin-transfer torques, which are mechanisms by which spin-polarized electrical currents can transfer their spin angular momentum to ferromagnets and (perhaps) antiferromagnets to reorient their magnetic moments. Already it has been shown that spin transfer can provide much stronger torques per unit current compared to using conventional magnetic fields, and spin torques can efficiently drive magnetic switching and precession. The proposed work will invent new experimental techniques to enable quantitative measurements of the strength and direction of spin torques in ferromagnetic layers. It will advance the technology of ultrafast electrical measurements and time-resolved x-ray microscopy to understand the magnetic dynamics that can be excited by spin torques. The project will also extend the study of spin torques to new classes of materials, specifically magnetic nanoparticles and antiferromagnets, for which interesting effects are predicted but no definitive experiments have been performed. The impact of project will be to advance basic understanding of electron spin dynamics and to provide information and experimental techniques that will be needed for the development of spin-torque-driven magnetic memories, frequency-tunable nanoscale microwave sources, and other technologies. The graduate and undergraduate students supported by the project will also gain an excellent interdisciplinary training in nanoscience.