RII Track 4: Non-Reciprocal Spin-Wave Engineering in Chiral Magnets

波存在于我们生活的许多方面，从通信到计算，都是一个深入研究的主题。特别是，由于移动用户和物联网的爆炸式增长对移动数据的需求不断增长，微波和毫米波已成为下一代技术(如5G/毫米波无线网络)的重点。然而，由于缺乏合适的材料，可重构高频器件和组件的制造一直是一个挑战。手性和磁性超材料在促进非对称自旋波传播方面的最新进展有望制造基于自旋波的微波环行器和二极管。这些自旋波是高度可配置的，因为手性磁体和非对称磁性多层膜中的磁相互作用可以定制，并且这些材料对外部磁场和激光脉冲高度敏感，以便进一步操纵。这种可配置、高能效和多功能的微波组件的展示将为新的高频通信设备铺平道路，这些设备可用于各种应用，包括娱乐、安全和远程患者治疗。俄克拉荷马州立大学和博尔德NIST的纳米级自旋动力学小组的合作将加快材料发现和设备表征，以实现从几GHz到THz频率的卓越和可重新配置的微波组件。这一研究将促进对手性磁性材料中非互易自旋波传播的基本认识。手性磁性材料中的非互易自旋波是由于反转对称性的破坏而引起的非对称交换相互作用。与光波或其他波相比，这些自旋波不是微不足道的，但通过调整磁相互作用，施加外部电场和磁场，或者用超短脉冲激发，它们可以非常容易处理。磁相互作用的控制将通过磁性材料和相邻金属层的工程界面来实现，以最大限度地减少磁振子散射，但保持高的非互易性。数值微磁模拟将用于优化器件性能，并更好地了解复杂异质结构中的自旋波传播。为此，该团队将(I)生长和合成低阻尼手性磁性材料和薄膜，(Ii)精确表征它们的结构和磁性，(Iii)制造微米和纳米尺度的器件，以开发器件概念。宽带铁磁共振光谱学、磁学、布里渊光散射谱、磁传输和外差磁光微波显微技术是本次研究中使用的技术。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Waves are in many parts of our lives, from communication to computation, and are a subject of intense research. In particular, micro and millimeter waves have been paid great attention for next-generation technologies, e.g., 5G/millimeter-wave wireless network, due to the ever-increasing demand in mobile data by the explosion of mobile users and IoT. However, the fabrication of reconfigurable high-frequency devices and components has been a challenge due to the lack of appropriate materials. Recent developments in chiral and magnetic meta-materials that facilitate asymmetric spin-wave propagation are promising for creating microwave circulators and diodes based on spin waves. These spin waves are highly configurable because the magnetic interactions in chiral magnets and asymmetric magnetic multilayers can be tailored, and these materials are highly sensitive to external magnetic fields and laser pulses for further manipulation. The demonstration of such configurable, power-efficient, and versatile microwave components will pave the way towards new high-frequency communication devices, which can be used in various applications, including entertainment, security, and remote patient treatment.The joined effort between Oklahoma State University and Nanoscale Spin Dynamics group at NIST, Boulder, will accelerate materials discovery and device characterization for superior and reconfigurable microwave components that can operate from a few GHz up to THz frequencies. The proposed research will advance the fundamental understanding of non-reciprocal spin-wave propagation in chiral magnetic materials, which is caused by asymmetric exchange interaction in them due to the broken inversion symmetry. These spin-waves are non-trivial compared to light or other waves, but they can be highly tractable by tailoring magnetic interactions, applying external electric and magnetic fields, or exciting with ultrashort pulses. Control of magnetic interactions will be achieved by engineering interfaces of magnetic material and adjacent metal layers to minimize magnon scattering but maintain high non-reciprocity. Numerical micromagnetic simulations will be used to optimize device performance and to better understand spin-wave propagation in complex heterostructures. For this purpose, the team will (i) grow and synthesize low-damping chiral magnetic materials and thin films, (ii) precisely characterize their structural and magnetic properties, and (iii) fabricate micro and nanoscale devices for the development of device concepts. Broadband ferromagnetic resonance spectroscopy, magnetometry, Brillouin light scattering spectroscopy, magnetotransport, and heterodyne magneto-optical microwave microscopy are the techniques to be employed in this investigation.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.