Magnetic Relaxation and Dynamics in Ferromagnetic Nanostructures

技术概述：该奖项支持旨在开发自洽输运和磁理论的理论研究，该理论能够解决由于非平衡传导电子和磁化之间的微观相互作用而产生的磁化衰减和动力学。最近在磁性纳米结构中发现的许多现象源于自旋输运性质和磁化动力学之间的相互作用。磁化衰减是分析磁化动力学中的一个关键成分，在微观上是最不被理解的。PI旨在发展一种磁化动力学的微观理论，以便更好地分析和预测在更快、更密集的磁存储和存储设备中出现的新现象。对磁化过程的详细理解关键取决于磁化松弛。本程序旨在通过同时求解非平衡传导电子的输运方程和局域磁化的磁化动力学来建立磁化驰豫理论。有限温度下的磁化驰豫和随机磁场都是由传导电子与局域磁化强度的微观相互作用得到的。重点研究了包括非局部阻尼的时间相关性在内的阻尼动力学过程。该理论将消除由于在Landau-Lifshitz-Gilbert方程中使用一个恒定的阻尼参数和一个不相关的随机场(“白噪声”)而造成的物理不一致性。该理论的几个应用是磁区壁动力学。热辅助磁化反转，以及磁化驰豫的大小依赖。非技术概述：该奖项支持旨在开发磁性材料实用理论的理论研究，该理论将改进磁性特性如何随时间变化的理论描述。这项研究还将解决磁技术开发中的关键问题。该理论将广泛应用于各种新兴的磁存储设备和磁随机存取存储器。将通过与一个工业伙伴建立合作关系，促进与工业界交流知识和研究成果。该项目与业界感兴趣的问题的直接联系，以及该项目提供的研究生和研究生教育经验，有助于提高美国的竞争力。

TECHNICAL SUMMARY:This award supports theoretical research aimed at developing a self-consistent transport and magnetic theory capable of addressing the magnetization damping and dynamics due to microscopic interactions between non-equilibrium conduction electrons and magnetization. Many recently discovered phenomena in magnetic nanostructures originate from the interplay between the spin transport properties and magnetization dynamics. The magnetization damping, a key component in analyzing magnetization dynamics, is microscopically least understood.The PI intends to develop a microscopic theory of magnetization dynamics so that new phenomena displayed in faster and denser magnetic storage and memory devices can be better analyzed and predicted. A detail understanding of the magnetization process depends critically on the magnetization relaxation. The present program intends to build the theory of magnetization relaxation by simultaneously solving the transport equation for the non-equilibrium conduction electrons and the magnetization dynamics for the local magnetization. Both the magnetization relaxation and the random magnetic field at finite temperature will be derived from the microscopic interaction between conduction electrons and the local magnetization. Emphasis is placed on the dynamical process of damping that includes the temporal correlation of non-local damping. The theory will remove the physical inconsistency imposed by using a constant damping parameter and an uncorrelated random field ("white noise") in the landau-Lifshitz-Gilbert equation. Several applications of the theory are domain wall dynamics. heat-assisted magnetization reversal, and the size dependence of magnetization relaxation.NON-TECHNICAL SUMMARY:This award supports theoretical research aimed at developing a practical theory of magnetic materials that would provide an impoved theoretical description of how magnetic properties change in time. The research will also address key issues in magnetic technology development. The theory will be broadly applied to various emerging magnetic storage devices and magnetic random access memory. The exchange of knowledge and research results with industry will be facilitated through established collaboration with an industrial partner. The direct connection to problems of interest to industry and the graduate and postgraduate educational experience that this project provides contributes to enhancing American competitiveness.