Magnetic Relaxation and Dynamics in Ferromagnetic Nanostructures

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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.