Development of tunable nanomagnetic microwave oscillators and circuits

该项目将研究基于磁点接触的纳米器件中自旋转移诱导磁化振荡的机制，并探索控制其特性的方法。为了提高器件之间的变异性，减小实际应用中产生的线宽，了解磁化动力学的空间特性及其与器件几何和物理条件的关系是很重要的。为了实现这些目标，将结合电子光谱学和两种成像技术--布里渊光散射显微镜和X射线二向色性显微镜--来表征振荡器的空间和光谱特性。为了了解器件结构的作用，将探索两种新的磁性几何结构，它们将能够独立控制器件中磁性层的配置。利用磁约束效应和动态反馈设计具有更好振荡特性的纳米磁振荡器。将实现两种类型的反馈，包括谐振电路和电磁耦合的有源外部反馈。后者将通过锁相到二次谐波，也称为参数泵浦，或其他更高阶锁相效应来实现。该项目的主要成果将是全面测量自旋转移引起的磁化动力学，这将导致对纳米系统中自旋转移和磁化动力学的影响有一个更好的基础理解。从拟议的测量中获得的信息将被用于开发控制和修改纳米结构中的磁动力学的新方法。该项目将有助于开发磁性显微镜和光谱学技术，以及时间分辨显微测量。该项目的主要变革性方面将是通过使用新的测量技术实现对磁性纳米设备的电流感生动力学性质的定性新水平的理解，以及新型有源磁性设备的开发。该项目将有助于开发新的纳米尺度磁性测量技术，包括光谱学和时间分辨显微镜。除了在微波技术方面的实际应用，该项目还将激励更广泛的纳米磁性设备科学和工程研究领域，以及与磁性纳米振荡器共享基本特性的磁记忆和逻辑设备的设计和实现。该项目将有助于参与其实施的学生的专业发展，通过小组级别的互动促进PI小组中的其他学生，以及将在合作机构和国家设施参与测量的更大学生和研究人员群体，以及那些参加会议和研讨会并展示研究结果的人。通过PI对本科生研究的持续承诺，以及积极参与几个本科生暑期研究项目，对本科生专业发展的影响将得到加强。将专门针对一名女性和/或少数族裔学生参与该项目。

The project will address the mechanisms of spin transfer-induced magnetization oscillations in nanodevices based on magnetic point contacts, and explore the methods to control their characteristics. In order to improve the variability among the devices and reduce the generation linewidth for practical applications, it is important to understand the spatial properties of magnetization dynamics and their relationship with the device geometry and physical conditions. To accomplish these goals, a combination of electronic spectroscopy and two imaging techniques, Brillouin light scattering microscopy and x-ray dichroism microscopy, will be employed for characterization of spatial and spectral properties of oscillators. To understand the role of device structure, two new magnetic geometries will be explored that will enable independent control of the configurations of the magnetic layers in the devices. Nanomagnetic oscillators with improved oscillation characteristics will be designed by employing magnetic confinement effects as well as dynamical feedback. Two types of feedback will be implemented including a resonant circuit and an electromagnetically coupled active external feedback. The latter will be implemented through phase locking to second harmonic, also known as parametric pumping, or other higher order phase locking effects.Intellectual merit. The main outcome of the project will be comprehensive measurement of the magnetization dynamics induced by spin transfer, which will lead to an improved fundamental understanding of the effects of spin transfer and magnetization dynamics in nanoscale systems. The information obtained from the proposed measurements will be used to develop new methods to control and modify magnetic dynamics in nanostructures. The project will contribute to development of magnetic microscopy and spectroscopy techniques, as well as time-resolved microscopic measurements. The main transformative aspect of the project will be a qualitatively new level of understanding of current-induced dynamical properties of magnetic nanodevices achieved by using new measurement techniques, as well as development of novel active magnetic devices.Broader impacts. The project will contribute to the development of new nanoscale magnetic measurement techniques involving spectroscopy and time-resolved microscopy. In addition to practical applications in microwave technology, the project will invigorate the broader research area of science and engineering of nanomagnetic devices, with additional benefits for design and implementation of magnetic memory and logic devices that share the fundamental properties with magnetic nano-oscillators.The project will contribute to professional development of the students involved in its implementation, other students in the PI's group via group-level interactions, as well as a much larger group of students and researchers that will be involved in the measurements at the collaborating institution and the national facility, and those attending conferences and seminars where the results of the research will be presented. The impact on the professional development of undergraduate students will be enhanced by the continued commitment of the PI to undergraduate student research, and active involvement in several undergraduate summer research programs. A female and/or a minority student will be specifically targeted for the participation in the project.