Magnetic Relaxation and Dynamics in Ferromagnetic Nanostructures

该奖项支持旨在开发自洽传输和磁性理论的理论研究，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引起的磁化阻尼和动力学。 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。 磁化阻尼是分析磁化动力学的一个关键组成部分，微观上了解最少。PI打算发展磁化动力学的微观理论，以便更好地分析和预测更快，更密集的磁存储和存储设备中显示的新现象。 对磁化过程的详细理解关键取决于磁化弛豫。 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部磁化的磁化动力学来建立磁化弛豫理论。 有限温度下的磁化弛豫和随机磁场都是由传导电子与局部磁化之间的微观相互作用导出的。 重点放在阻尼的动态过程，包括非局部阻尼的时间相关性。 该理论将消除在Landau-Lifshitz-吉尔伯特方程中使用常数阻尼参数和不相关随机场（“白色噪声”）所造成的物理不一致。 该理论的几个应用是畴壁动力学。热辅助磁化反转，以及磁化弛豫的尺寸依赖性。非技术摘要：该奖项支持旨在开发磁性材料实用理论的理论研究，该理论将提供磁性如何随时间变化的改进理论描述。 该研究还将解决磁性技术发展中的关键问题。 该理论将广泛应用于各种新兴的磁存储器件和磁随机存取存储器。 将通过与一个工业伙伴建立的合作关系，促进与工业界交流知识和研究成果。 该项目与工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.