RII Track 4: Metrology and spectroscopy of individual nanomagnets dynamics using quantum sensor-based (NV- center) nano-magnetometry

被称为纳米磁体的磁性纳米结构是新兴信息存储技术（诸如磁性随机存取存储器（MRAM）设备）的基础。信息科学和技术领域的爆炸性增长要求新的存储技术具有更小的记录位、密集封装、快速、低成本和节能的特点。因此，用于构建磁存储器的磁性纳米结构需要在许多设备上小、快和均匀。然而，由于几何缺陷、不均匀的材料成分和制造相关的缺陷，相同设计的纳米磁体的性能彼此偏离。对单个纳米磁体的详细诊断对于解开形状、尺寸和制造缺陷对纳米磁体性能的影响是必要的。然而，纳米磁体的性质的测量是复杂的，因为它们很小，埋在许多层之下。拟议的项目旨在测量单个纳米磁体的特性。所提出的测量将揭示是什么原因导致纳米磁体的性能相互偏离。拟议的研究将与内布拉斯加大学林肯分校（UNL）的合作者一起进行。内布拉斯加州纳米级设施的最先进研究工具将用于设计、制造和测量纳米磁体的特性。获得的新知识将被应用到教育计划中，这将赋予未来的STEM劳动力。磁性纳米结构的受限几何形状导致自旋动力学偏离大块薄膜。除了改变共振频率之外，还存在多个自旋波模式。在边缘处的内部磁场中的强不均匀性允许自旋波定位在距离边缘几纳米内。纳米图案化过程中引起的损伤，如杂质，边缘和界面粗糙度，可以显着修改自旋动力学。随着尺寸的减小，边缘和缺陷的作用变得至关重要，因为由于边缘粗糙度和缺陷密度的轻微偏差，纳米磁体之间的自旋动力学偏离。自旋动力学的测量是复杂的，因为纳米磁体通常被埋在磁性层下，并且传统的计量工具和常规的磁性测量都不够灵敏。此外，很难从许多类似纳米磁体的平均响应中检索单个纳米磁体的隐蔽自旋动力学。拟议的研究调查的自旋波激发模式的光谱特性的个别磁性纳米结构。总体目标是了解控制磁性纳米结构的动态特性的基本器件物理，并了解器件之间的缺陷，非均匀性和几何缺陷的来源及其在器件性能中的作用。所提出的新方法是基于扫描氮空位（NV-）中心的磁力测量结合实时锁定和跟踪NV-中心的磁共振峰。建议的方法充分利用了NV中心的独特属性，其磁共振频率会因附近磁场的变化而发生变化。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Magnetic nanostructures, referred to as nanomagnets, are the foundation of emerging information storage technologies such as magnetic random access memory (MRAM) devices. Explosive growth in information science and technology sectors demands new storage technologies that are smaller recording bits, densely packed, fast, low-cost, and energy-efficient. Therefore, the magnetic nanostructures used to build magnetic memory need to be small, fast, and uniform across many devices. However, identically engineered nanomagnets' performances deviate from each other due to geometric imperfections, non-uniform material compositions, and manufacturing-related defects. A detailed diagnosis of individual nanomagnets is necessary to unravel the effects of shape, sizes, and manufacturing imperfections on nanomagnets' properties. However, the measurement of nanomagnets' properties is complicated because they are small and buried under many layers. The proposed project aims to measure the properties of individual nanomagnets. The proposed measurement would expose what causes the nanomagnets' performances to deviate from each other. The proposed research will be performed with a collaborator at the University of Nebraska – Lincoln (UNL). The state-of-the-art research tools at the Nebraska Nanoscale Facility will be used to design, fabricate, and measure nanomagnets' properties. The obtained new knowledge will be implemented into the education plans, which empower the future STEM workforce.The confined geometry of magnetic nanostructures causes spin dynamics to deviate from bulk thin films. In addition to shifting the resonance frequency, multiple spin-wave modes are present. The strong inhomogeneity in the internal magnetic field at the edge allows spin-wave to localize within a few nanometers from the edge. Damages induced during nanopatterning, such as impurities, edge, and interface roughness, can significantly modify spin dynamics. The edges and defects' roles become critical with decreasing size as the spin dynamics deviate among nanomagnets due to a slight deviation in edge roughness and defect densities. The measurement of spin dynamics is complicated because nanomagnets are often buried under nonmagnetic layers, and both conventional metrology tools and routine magnetic measurements are not adequately sensitive. Furthermore, it is difficult to retrieve an individual nanomagnet's covert spin dynamics from the average response of many similar nanomagnets. The proposed research investigates the spectroscopy of spin-wave excitation modes characteristics of individual magnetic nanostructures. The overall goals are to understand the fundamental device physics that controls the dynamic properties of magnetic nanostructures and to understand the source of defects, non-uniformity, and geometrical imperfection among devices and their roles in device performances. The proposed novel method is scanning Nitrogen-Vacancy (NV-) center-based magnetometry combined with real-time locking and tracking of NV- center's magnetic resonance peak. The proposed approach leverage the unique properties of NV- centers whose magnetic resonance frequency shifts due to change in the magnetic field in the vicinity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.