Nonlinear Spin Waves in Magnetic Films: New Concepts and Applications

Colorado State University, Fort Collins CO

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** Chaos and solitons are two important branches of nonlinear science that have attracted interest over a wide range of disciplines, including mathematics, physics, biology, and engineering. Chaos is the idea that outcomes are highly sensitive to initial conditions: a butterfly flaps its wings in New York and there is a storm in Tokyo. Solitons are localized waves like tsunamis, and frequently occur in weakly nonlinear systems. Usually one believes that chaos and solitons are opposed to each other ? a soliton can be strongly perturbed and yet persists, for example, making it difficult to stop, say, a tsunami. This project will seek connections between chaos and solitons. Specifically, the project will take advantage of spin waves (a travelling disturbance in the magnetic order) in magnetic film systems to explore these connections. On the applied side, the project will develop a new secure communication scheme that exploits the solitons in feedback rings. This is a joint program between one experimental group and one theoretical group in two universities. Through the training of students in both experimental and theoretical nonlinear dynamical methods, the project will help young scientists cross the divide between ?theory land? and physical reality, leading to both better experiments and better theories. The education portion also includes the incorporation of nonlinear dynamics and chaos into undergraduate and graduate curricula and reaching out to students in disadvantaged high schools in Colorado. ****TECHNICAL ABSTRACT**** This project will take advantage of spin waves in magnetic film systems to explore a possible crossover between solitons and chaos. The project will explore ?chaotic carrier solitons? ? solitons with chaotic carrier waves. A magneto-dynamic probe will be used to study the evolution of a pulse of chaotic spin waves and the formation of an envelope soliton from such a pulse. The project will also explore ?chaotic solitons? ? solitons that have coherent carrier waves but exhibit chaotic behaviors in time. The work will include the study of chaotic soliton excitation through modulational instability and chaotic solitons in magnetic film feedback rings. On the applied side, the project will develop a new secure communication scheme that exploits the soliton-associated Fermi-Pasta-Ulam recurrence in feedback rings. For all the projects, theoretical modeling will inspire, support, and interpret experimental work. The education portion focuses on the incorporation of nonlinear dynamics and chaos into undergraduate and graduate curricula both through core courses and through the design of new electives, as well as training of undergraduate and graduate researchers and reaching out to students in disadvantaged high schools.