Mingzhong WU
Department of Physics, Colorado State University, Fort Collins, CO 80523, USA
E-mail: 该邮件地址已受到反垃圾邮件插件保护。要显示它需要在浏览器中启用 JavaScript。
时间：2014年7月31日上午10：00
地点：唐仲英楼A213
Abstract
Nonlinear spin waves in magnetic systems are of both fundamental and technological interest. This presentation will report the excitation of chaotic spin waves in magnetic thin films through three-wave nonlinear processes. The presentation will begin with introductions to chaos and spin waves and will then report two different chaotic spin wave experiments.
The experiments made use of a magnetic yttrium iron garnet (YIG) thin film strip and two microstrip line transducers placed over the YIG strip to excite and detect spin waves. The output signal from the detection transducer was fed back to the excitation transducer through an adjustable microwave attenuator and a linear microwave amplifier. The signal from such a feedback ring was sampled through a directional coupler, with feeds to a spectrum analyzer for frequency analysis and a fast oscilloscope for temporal signal measurements. Experiments were carried out in two regimes. In the first regime, a magnetic field was applied in the plane of the YIG film strip and parallel to the length of the strip, and the excitation of chaotic spin waves was realized through three-wave interactions between backward volume spin waves of different frequencies. In the second regime, a magnetic field was applied in the plane of the YIG strip and perpendicular to the length of the strip. In this case, the chaotic excitation was realized through three-wave interactions between surface and backward volume spin waves. The development of chaotic dynamics with increasing ring gain was studied. The chaotic nature of the measured signals was confirmed by irregular waveforms, broad spectra, finite correlation dimensions, and decaying auto-correlation profiles. The features of the measured chaotic signals for radar applications were also explored.
Mingzhong Wu received his Ph.D. in Solid State Electronics from Huazhong University of Science and Technology in 1999, joined the faculty of Colorado State University (CSU) in 2007, and is currently an Associate Professor in Physics at CSU. He is interested in many topics in magnetics. His current research areas include magnetization dynamics, spintronics, nonlinear spin waves, multiferroics, and microwave magnetic materials and devices. He has authored/coauthored 105 publications, including 1 book, 4 book chapters, and 14 papers in PRL. He is currently serving as the Chair of the IEEE Magnetics Society Education Committee and an Associate Editor for IEEE Magnetics Letters.