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

磁性纳米结构，被称为纳米磁体，是新兴信息存储技术的基础，如磁性随机存取存储器（MRAM）设备。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、密集的封装、快速、低成本和节能。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巧、快速和均匀。然而，由于几何缺陷、不均匀的材料成分和制造相关缺陷，相同工程的纳米磁铁的性能会相互偏离。对单个纳米磁体的详细诊断是必要的，以揭示形状、尺寸和制造缺陷对纳米磁体性能的影响。然而，由于纳米磁体体积小且埋在许多层下，因此测量纳米磁体的性能是复杂的。该计划旨在测量单个纳米磁铁的特性。所提出的测量方法将揭示导致纳米磁铁性能相互偏离的原因。拟议的研究将与内布拉斯加州大学林肯分校（UNL）的合作者一起进行。内布拉斯加州纳米设施最先进的研究工具将用于设计、制造和测量纳米磁铁的特性。获得的新知识将被实施到教育计划中，从而增强未来STEM劳动力的能力。磁性纳米结构的受限几何结构导致自旋动力学偏离体膜。除了改变共振频率外，还存在多种自旋波模式。边缘处内部磁场的强不均匀性使得自旋波可以定位在距离边缘几纳米的范围内。在纳米图形化过程中引起的损伤，如杂质、边缘和界面粗糙度，可以显著地改变自旋动力学。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会发生偏差，因此随着尺寸的减小，边缘和缺陷的作用变得至关重要。由于纳米磁体通常埋在非磁性层下，传统的测量工具和常规的磁性测量都不够灵敏，因此自旋动力学的测量非常复杂。此外，很难从许多相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。本研究研究了单个磁性纳米结构的自旋波激发模式的光谱特征。总体目标是了解控制磁性纳米结构动态特性的基本器件物理，了解器件之间缺陷、不均匀性和几何缺陷的来源及其在器件性能中的作用。提出了一种基于扫描氮空位（NV-）中心的磁强计，结合实时锁定和跟踪NV-中心的磁共振峰的方法。所提出的方法利用了NV-中心的独特性质，其磁共振频率由于附近磁场的变化而发生变化。该奖项反映了美国国家科学基金会的法定使命，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.