Field-and Current-Driven Domain-Wall Dynamics in Microstructures

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****Technical Abstract****Magnetic domain walls can be manipulated at high-speeds and on nanometer spatial scales by applied magnetic fields and electric currents. Modern nanotechnology methods can be used to engineer and fabricate nanometer-scale magnetic wires. These model one-dimensional structures can serve as conduits for electric current and for guiding magnetic domain walls. This project utilizes magneto-optic techniques to probe the high-speed manipulation of magnetic domain walls in fabricated nanometer-scale magnetic structures. The goal of the work is to characterize and understand the (spin-torque) mechanisms that: 1) allow high-speed manipulation of magnetization on nanometer spatial scales by electric currents, and that 2) govern energy loss and damping. The work is directly related to existing and emerging technology that relies on high-speed manipulation of magnetism on small spatial scales: magnetic meta materials, memory and logic structures, and imaging, radar and telecommunication technology. The research involves state-of-the-art materials synthesis and nanofabrication techniques, and addresses new phenomena that occur as a result of nanometer spatial constraints. It provides excellent education and training opportunities for the students and postdoctoral associates who work on the projects.****Non-Technical Abstract****Electron spins in one-dimensional nanometer-scale structures of magnetic material (magnetic nanowires) form regions of uniform magnetization (domains) separated by a domain wall in which spin orientation reverses between the two opposing spin domains. The spin configuration in the nanostructure can be manipulated by the application of a magnetic field or an electric current. The ability to manipulate and probe electron spins (local magnetism) on nanometer scales at high speeds is technologically important: it provides the basis for magnetic cellular logic and related new device technology that could extend and improve existing microelectronic devices that digitally store and process information. This project explores high-speed manipulation of electron spins in magnetic nanostructures. The objective of the work is to determine and understand the mechanisms that allow electric current manipulation of spins and discover how material composition and geometrical constraints govern and limit the control of local magnetism on nanometer scales. The project provides a good venue for training the next generation of scientists, technologists, and teachers because it involves new phenomena and requires application of current state-of the-art research instruments and materials science/nanoscience technology.