Current-driven magnetic sources at microwave frequency

微波频率源是从移动的设备到通信再到计算等应用技术的关键组成部分。 有必要开发极其紧凑的源，并开发灵活的源，这意味着它们的频率可以在尽可能短的时间内改变。 一个很好的候选者是纳米磁性振荡器，它通过应用直流电流产生高度可调的微波频率。 这些磁振荡器单独存在输出功率不足、线宽过宽等技术上的应用问题，但如果将它们连接起来，使它们的微波输出同步，就可以克服功率和线宽的问题。 虽然之前已经将一些磁性振荡器耦合在一起，但很难设计它们，以便它们以可扩展的方式同步。 此外，了解振荡器之间的纳米级磁相互作用是一个有趣的科学问题，其影响超出了技术。 本项目将在跨学科的环境中培养本科生和研究生，并为科学教师提供研究经验。在本提案中，研究团队引入了三个创新概念，以克服可缩放同步纳米磁性振荡器的挑战。 首先，他们提出设计，建模和制造横向磁振荡器驱动的自旋霍尔效应在一个周期性的阵列使用的概念，从新兴领域的磁。 其次，他们将采用时空磁显微镜来实验性地检查这些结构的动力学模式，这将有助于揭示单个STO如何与真实的设备中的邻居耦合。 这是横向自旋霍尔振荡器器件的最新突破所提供的新机会，因为磁振荡器网络以前是基于直接注入、垂直传输器件的。 在这些设备中，磁性层被掩埋并且非常难以成像。成像的可用性为基于特定的设备级洞察设计设备创造了机会。第三个创新概念是使用频闪成像来研究磁模式的损耗机制。 传统上，频闪方法对非相干过程是盲目的，如自旋波模式之间的耦合，这可能导致动态增强的磁阻尼。通过结合与频闪仪相称和不相称的微波驱动场，研究小组将研究能量如何在有用的磁模式和寄生磁模式之间转移。 这项研究的见解将使新的和更好的设计，以同步磁性振荡器。

Microwave frequency sources are a critical component of technology for applications ranging from mobile devices to communications to computing. There is a need to develop extremely compact sources, and to develop sources that are agile, meaning their frequency can be shifted on the shortest possible timescale. A good candidate is nanoscale magnetic oscillators that produce highly tunable microwave frequencies through the application of d.c. current. Singly, these magnetic oscillators have insufficient output power and too broad a linewidth to be applied in technology, however, if they can be connected to each other so that they synchronize their microwave output, both the power and the linewidth problem can be overcome. While a few magnetic oscillators have been coupled together previously, it has been difficult to design them so that they synchronize in a scalable way. Additionally, understanding the nanoscale magnetic interactions between oscillators is an interesting scientific problem that has implications beyond technology. This project will train both undergraduate and graduate students in an interdisciplinary environment, and it will offer research experience for science teachers.In this proposal, the research team introduces three innovate concepts to overcome the challenge of scalably synchronizing nanoscale magnetic oscillators. First, they propose to design, model and fabricate lateral magnetic oscillators driven by the spin Hall effect in a periodic array using concepts from the emerging field of magnonics. Second, they will employ spatiotemporal magnetic microscopy to experimentally examine the dynamical modes of these structures, which will help reveal how individual STOs are coupled to its neighbors in real devices. This is a new opportunity offered by recent breakthroughs in lateral spin Hall oscillator devices because magnetic oscillator networks were previously based on direct injection, vertical transport devices. In those devices, the magnetic layers are buried and very difficult to image. The availability of imaging creates an opportunity to engineer devices based on specific, device-level insight. The third innovate concept is to use stroboscopic imaging to study loss mechanisms from magnetic modes. Traditionally, stroboscopic methods are blind to incoherent processes, like the coupling between spin wave modes that can lead to dynamically enhanced magnetic damping. By combining microwave driving fields that are both commensurate and incommensurate with the stroboscope, the research team will examine how energy can be transferred between useful magnetic modes and spurious magnetic modes. The insights from this research will enable new and better designs to synchronize magnetic oscillators.