From Solitons to Precessional Dynamics and Chaos - Nonlinear Spin Waves in Thin Films

从孤子到进动动力学和混沌 - 薄膜中的非线性自旋波

• 批准号: 0108797
• 负责人: Carl Patton
• 金额: $ 34.5万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-11-01 至 2004-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0108797&HistoricalAwards=false
• 关键词: Solitons; Precessional; Dynamics; Chaos; Nonlinear

This project deals with response of thin magnetic films to microwave radiation. Microwaves can produce novel responses in the films, such as magnetic envelope (MME) solitons. The thin films provide a powerful and versatile "test bed" for the study of high frequency nonlinear dynamics and the fundamental properties of the envelope solitons. The results are relevant to microwave nonlinear wave propagation in magnetic films and spin-off applications of these effects in microwave and millimeter wave thin film signal processing. In addition, there is substantial interest in dynamical nonlinear magnetization processes associated with flux reversal and spin injection in multi-layer films. The new program will focus on: (1) direct measurement of the spin waves associated with or generated by MME solitons; (2) the use of new time and space resolved probe techniques to measure the spatio temporal and wave vector make up of these pulses on a nanosecond or subnanosecond time scale; and (3) the nonlinear magnetization dynamics associated with modulational instability and chaos, free precession, and spin wave generation by spin injection. Graduate students and post-docs associated with the project receive excellent training in technical magnetism, using cutting-edge research tools. They are well equipped for careers in academe, industry or government.%%%This project studies the properties of correlated magnetic dipoles (similar to tiny compass needles) in magnetic thin films. In magnetic field, the dipoles rotate, or precess, much like the precession of a spinning top due to gravitational field. This leads to so-called nonlinear effects when the precession angle is large. Chains of such precessing dipoles can be used to form nonlinear pulses in the form of solitons. Such soliton pulses are very robust and can propagate without spreading. The precession can also lead to a switching in the direction of the overall magnetic moment of a film. Both solitons and switching can lead to other nonlinear effects such as the generation of new pulses and additional waves of precessing spins at different frequencies. The unique feature of the work is in the use of special probes to map the precession dynamics on a nanosecond time scale and a sub-millimeter distance scale. The results will be useful for the understanding of nonlinear dynamics in general, with long range applications in microwave signal processing and magnetic information storage. Graduate students and post-docs associated with the project receive excellent training in technical magnetism, using cutting-edge research tools. They are well equipped for careers in academe, industry or government.

本课题研究磁性薄膜对微波辐射的响应。微波可以在薄膜中产生新的响应，例如磁包络孤子。薄膜为研究高频非线性动力学和包络孤子的基本性质提供了一个强大而通用的“试验台”。研究结果与微波非线性波在磁性薄膜中的传播以及这些效应在微波和毫米波薄膜信号处理中的衍生应用有关。此外，人们对多层膜中与磁通反转和自旋注入相关的动态非线性磁化过程非常感兴趣。新计划将侧重于：(1)直接测量与MME孤子相关或由MME孤子产生的自旋波；(2)利用新的时间和空间分辨探针技术，在纳秒或亚纳秒时间尺度上测量这些脉冲的时空和波矢量；(3)与调制不稳定性和混沌、自由进动和自旋注入产生自旋波有关的非线性磁化动力学。与该项目相关的研究生和博士后接受技术磁力方面的优秀培训，使用尖端的研究工具。他们为学术、工业或政府的职业生涯做好了充分的准备。本课题研究磁性薄膜中相关磁偶极子（类似于微小的指南针）的性质。在磁场中，偶极子旋转或进动，很像引力场导致的旋转陀螺的进动。当进动角较大时，这导致了所谓的非线性效应。这样的进动偶极子链可以用来形成以孤子形式存在的非线性脉冲。这种孤子脉冲非常健壮，可以在不扩散的情况下传播。进动也会导致薄膜整体磁矩方向的改变。孤子和开关都可能导致其他非线性效应，例如产生新的脉冲和不同频率的自旋的额外波。这项工作的独特之处在于使用特殊的探针在纳秒时间尺度和亚毫米距离尺度上绘制岁差动力学。研究结果将有助于理解非线性动力学，在微波信号处理和磁信息存储方面具有广泛的应用。与该项目相关的研究生和博士后接受技术磁力方面的优秀培训，使用尖端的研究工具。他们为学术、工业或政府的职业生涯做好了充分的准备。