Nonlinear Waves Seminar - Mingzhong Wu
Mingzhong Wu, Department of Physics, Colorado State University
A fractal is a shape made of parts each of which is similar to the whole in some way. One can group fractals into two main categories, (i) exact fractals in which the same feature replicates itself on successively smaller scales and (ii) statistical fractals that display statistically similar features. Statistical fractals have been observed in a wide variety of physical systems, ranging from material structures to stock price fluctuations. In contrast, exact fractals are relatively rare in nature, though they can be very easily constructed by mathematical models.
This presentation will report on the experimental observation of exact fractals in nonlinear spin waves in magnetic materials. There will be two parts. Part I will be on soliton fractals in a feedback ring that consists of (1) a long and narrow magnetic Y3Fe5O12 (YIG) thin film strip that supports spin waves and (2) an amplifier that amplifies the output signal from the YIG strip and then fed it back to the input of the strip.1 Part II will be on spin-wave fractals in a quasi-1D magnonic crystal that consists of a YIG film strip with periodic transversal lines etched into the film.2
 “Observation of spin wave soliton fractals in magnetic film active feedback rings,” Mingzhong Wu, Boris A. Kalinikos, Lincoln D. Carr, and Carl E. Patton, Phys. Rev. Lett. 96, 187202 (2006).
 “Spontaneous exact spin-wave fractals in magnonic crystals,” Daniel Richardson, Boris A. Kalinikos, Lincoln D. Carr, and Mingzhong Wu, Phys. Rev. Lett. 121, 107204 (2018).
Biography: Mingzhong Wu received his Ph.D. in Solid State Electronics from Huazhong University of Science and Technology in China in 1999, joined the faculty of Colorado State University (CSU) in the USA in 2007, and is currently the Professor of Physics and the Director of CSU’s “Program of Research and Scholarly Excellence” Designated Center for Advanced Magnetics. He is interested in many research topics in magnetism and magnetic materials; his current research areas include magnetization dynamics, nonlinear spin waves, spintronics, and topological insulators. He has authored over 135 technical papers and 4 book chapters; he has also co-edited a book on magnetic insulators. He served as an Editor for IEEE Magnetics Letters (2012- 2016), and he is currently serving as an Editor for Physics Letters A. He is on the Editorial Advisory Board for the Journal of Applied Physics and the Editorial Board of Journal of Magnetism and Magnetic Materials. He served as the Education Committee Chair (2012-2015) and the Finance Chair (2015-2018) of the IEEE Magnetics Society, and he currently serves as the Technical Committee Chair of the Society.
Tuesday, April 9 at 4:00pm to 5:00pm
Engineering Center, ECOT 226
1111 Engineering Drive, Boulder, CO 80309