Nonlinear Theory Of Microwave Spin Torque Nano-Oscillators

众所周知，自旋极化电流注入可以完全补偿由于阻尼引起的能量耗散，并导致纳米磁体中的无阻尼磁化进动。 这些无阻尼磁化进动的频率由注入的自旋极化电流控制。 这些微波自旋力矩振荡器具有独特的性能，如纳米尺寸，辐射硬度，宽带锁相和快速频率调谐。 因此，微波自旋力矩振荡器成为近年来实验和理论研究的热点。学术价值：目前对微波自旋力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生成阈值的条件下有效。 本计画的目的是发展以非线性动力系统理论为基础的微波自旋力矩振荡器的分析，并适用于近及远产生临界条件。 本项目的主要研究目标是：1）研究自旋力矩纳米振荡器（STNO）相对于热产生的空间非均匀介质的稳定性（类自旋波）扰动，2）通过使用随机扰动磁化动力学方程和图上的随机过程理论的STNO的噪声和谱密度分析，3）利用Landua-Lifshitz-Slonczewski方程的Poisson噪声扰动分析STNOs的噪声; 4）利用分岔理论研究STNOs的锁相。 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。 拟议的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，也将通过ECE部门涉及本科生？的MERIT和GEMSTONE计划。 他们会为国家添砖加瓦吗在这一重要的新兴技术领域，美国拥有大量的人才。 这项研究也将有一个强大的国际合作的组成部分，它将作为一个工具，以扩大和加强现有的科学合作与意大利同事，博士。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.