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Physics Colloquium - Friday, Feb. 27th, 2009,
4:00 P.M.
E300 Math/Science
Center; Refreshments at 3:30 P.M. in
Room E200
Mark Novotny
Department of Physics and Astronomy
and
HPCC Center for Computational Sciences
Mississippi State University
Far from Equilibrium Processes in Magnetic Nanoparticles and Thin Films:
Experiments and Simulations: Hysteresis, Metastability, and a Dynamic Phase Transition
The concept of hysteresis in magnetic nanoparticles and thin magnetic films will be outlined, both the decades-old view and some of the required changes needed for ultra-thin magnetic layers at finite temperatures. One topic addressed will be how the hysteresis loop area depends on the frequency of the applied field. The existence of a Dynamic Phase Transition (DPT) in such hysteretic systems will be demonstrated. Results of large-scale simulations to determine the universality class of the DPT for highly-anisotropic thin film systems will be described. Experiments on ultra-thin multilayer magnetic structures comprised of [Co/Pt]_3 multilayers with a thickness of 0.4 nm will be discussed in detail, and evidence provided that a DPT has been seen experimentally in these magnetic systems.
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