Nonlinear Theory Of Microwave Spin Torque Nano-Oscillators

已知自旋极化电流注入可以充分补偿阻尼引起的能量耗散，从而在纳米磁体中产生无阻尼的磁化进动。这些无阻尼磁化进动的频率由注入的自旋极化电流控制。这些微波自旋转矩振荡器具有纳米级尺寸、辐射硬度、锁相带宽宽和频率快速调谐等独特性能。因此，微波自旋转矩振荡器一直是近年来实验和理论研究的热点。智力优势：目前对自旋转矩振荡器的研究大多采用经典的自旋波理论。这种自旋波方法仅在接近发电阈值的条件下有效。本课题的目标是建立基于非线性动力系统理论的微波自旋转矩振荡器的分析，并适用于近和远产生阈值条件。本课题的主要研究目标是：1)热致非均匀（类自旋波）扰动下自旋力矩纳米振荡器（STNO）的稳定性研究；2)利用随机摄动磁化动力学方程和图上随机过程理论分析STNO的噪声和谱密度；3)利用landva - lifshitz - slonczewski方程的Poisson-noise摄动分析STNO的噪声。4)分岔理论背景下STNOs锁相的研究。理论结果和预测将通过与数值模拟和实验的比较来验证。更广泛的影响：纳米科学和纳米技术有望对美国和世界经济产生持续和长期的影响，并有望在不久的将来成为增长的引擎。该研究在纳米自旋电子学领域具有潜在的变革性技术应用。这项研究将直接支持两名研究生，并将通过欧洲经委会参与本科生的研究。美国的MERIT和GEMSTONE项目。他们会给国家添彩吗？美国在这一重要的新兴技术领域的人才储备。这项研究还将具有强大的国际合作组成部分，它将作为扩大和加强与意大利同事之间现有科学合作的工具。G. Bertotti和C. Serpico，以及他们的学生。

It is known that spin-polarized current injection may fully compensate for energy dissipation due to damping and result in undamped magnetization precessions in nanomagnets. The frequencies of these undamped magnetization precessions are controlled by injected spin-polarized currents. These microwave spin-torque oscillators have unique properties such as nanoscale dimensions, radiation hardness, wide bandwidth of phase-locking and rapid frequency tuning. For this reason, the microwave spin-torque oscillators have been the focus of considerable experimental and theoretical research lately.Intellectual Merit: Currently spin-torque oscillators are mostly studied by using the classical spin-wave theory. This spin-wave approach is efficient only for near to generation threshold conditions. The goal of this project is to develop the analysis of microwave spin-torque oscillators based on the nonlinear dynamic system theory and applicable for both near and far from generation threshold conditions. The main objectives of the research work on this project will be 1) stability study of spin-torque nano-oscillators (STNO) with respect to thermally generated spatially non-uniform (spin-wave like) perturbations, 2) noise and spectral density analysis of STNOs by using randomly perturbed magnetization dynamics equations and the theory of stochastic processes on graphs, 3) noise analysis of STNOs by using Poisson-noise perturbations of Landua-Lifshitz-Slonczewski equations, and 4) the study of phase-locking of STNOs in the context of the bifurcation theory. Theoretical results and predictions will be verified through their comparison with numerical simulations and experiments.Broader Impact: Nanoscience and nanotechnology promise to have a continuing and long-term impact on the US and world economies, and are anticipated to be engines of growth in the near future. The proposed research has potentially transformative technological applications in the area of nano-spintronics. This research will directly support two graduate students, and will also involve undergraduate students via the ECE Department?s MERIT and GEMSTONE programs. They will add to the nation?s pool of talent in this important emerging area of technology. This research will also have a strong international collaboration component and it will serve as a vehicle to expand and strengthen the existing scientific collaborations with Italian colleagues, Drs. G. Bertotti and C. Serpico, as well as with their students.