Active antiferromagnetic materials for hosting hybrid magnonic functionalities

非技术描述反铁磁体是一类具有微观磁偶极矩的材料，它们的磁偶极矩与相邻材料的方向相反。它们拥有动态模式，这些模式是从每秒数十亿(GHz)到万亿(THz)周期的微观振荡中产生的。这对基于太赫兹通信、计算和传感设备的新兴技术非常重要。永磁体可以通过磁场磁化，而反铁磁体则高度抵抗外部控制。这使得操纵它们的磁性和开发基于这些材料的新技术变得困难。为了推进基于反铁磁体的技术，研究小组将合成旨在有效激发和操纵其动态性能的结构。材料的重点将是铁(Fe_2O_3)、铬(Cr2O_3)和镍(NiO)的反铁磁性氧化物。该团队将设计由反铁磁体和其他材料组成的薄膜结构中振荡模式之间的相互作用。国际和平研究所寻求通过让女性本科生和研究生参加实验室来扩大对STEM的参与。国际宣讲会还将组织研讨会和圆桌讨论会，具有相关技术背景的工业界女发言人将在正式和非正式场合与学生交流。其目标是开发和支持一个网络，使妇女能够实现她们的职业抱负，并就她们的技术技能如何为STEM劳动力做出贡献提供更广泛的视角。技术说明在反铁磁材料和超材料中，磁子存在于从数十GHz到THz的广泛频率范围内。然而，在亚太赫兹或太赫兹水平上强有力地操纵和激发反铁磁磁振子光谱的实用方法还没有被证明。这主要是由于反铁磁序对外场不敏感所致。这些超快磁激发的功能化为解锁目前尚不存在的下一代太赫兹电子学和超快磁记忆技术提供了巨大的潜力。该团队将反铁磁性磁子功能化的方法结合了自旋电子学的主题和混合量子磁振子中的新兴概念。具体地说，利用各种声学和光学模式之间的磁振子-磁振子相互作用来对磁振子能谱施加控制。在这个项目中，溅射沉积技术被用来合成异质结构，这种异质结构要么模仿反铁磁体，要么在整体结构中加入块状反铁磁体。类似于反铁磁体的异质结构类似于合成反铁磁体，由多个由非磁性间隔材料耦合在一起的铁磁性薄膜组成。在给定的结构中，磁性层的总数和间隔层材料的选择是激发磁振子和产生磁振子-磁振子相互作用的关键因素。通过合成基于块状反铁磁体的异质结构，该团队依靠空间均匀的反铁磁磁子和短波长铁磁磁子之间的相互作用来控制亚太赫兹和太赫兹区域的能级谱。传统的铁磁共振波谱、自旋扭矩铁磁共振波谱和频域太赫兹波谱技术被用于表征这些样品。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。

Nontechnical DescriptionAntiferromagnets are a class of materials with microscopic magnetic dipole moments that align in the opposite direction of their neighbors. They possess dynamic modes that emerge from microscopic oscillations at frequencies ranging from billions (GHz) to trillions (THz) of cycles per second. This is important for emerging technologies based on THz devices for communications, computing and sensing. Whereas permanent magnets can be magnetized through a magnetic field, antiferromagnets are highly resistant to external control. This makes it difficult to manipulate their magnetic properties and develop new technologies based on these materials. To advance technologies based on antiferromagnets, the research team will synthesize structures designed to effectively excite and manipulate their dynamic properties. The materials focus will be on antiferromagnetic oxides of iron (Fe2O3), chromium (Cr2O3), and nickel (NiO). The team will engineer interactions between the oscillating modes within thin film structures composed of antiferromagnets and other materials. The PI seeks to broaden participation in STEM by involving female undergraduate and graduate students in the laboratory. The PI will also organize seminars and round table discussions where women speakers from industry, with relevant technical backgrounds, engage with the students in both formal and informal settings. The objective is to develop and support a network that empowers women to achieve their career aspirations and provides a broader perspective on how their technical skills can contribute to the STEM workforce.Technical DescriptionWithin antiferromagnetic materials and metamaterials, magnons exist across a wide range of frequencies, spanning from tens of GHz to THz. However, practical methods to robustly manipulate and excite the antiferromagnetic magnon spectrum at the sub-THz or THz level have yet to be demonstrated. This is primarily due to the insensitivity of antiferromagnetic order to external fields. The functionalization of these ultrafast magnetic excitations holds significant potential for unlocking next-generation THz electronics and ultrafast magnetic memory technologies that are currently nonexistent. The team's approach to functionalize antiferromagnetic magnons combines motifs from spintronics with emerging concepts in hybrid quantum magnonics. Specifically, magnon-magnon interactions between various acoustic and optical modes are leveraged to exert control over the magnon energy spectrum. In this project, sputter deposition techniques are employed to synthesize heterostructures that either emulate antiferromagnets or incorporate bulk antiferromagnets into the overall structure. The heterostructures resembling antiferromagnets are akin to synthetic antiferromagnets, comprising multiple ferromagnetic films coupled together by a non-magnetic spacer material. The total number of magnetic layers and the choice of spacer layer materials in a given structure are key factors in exciting magnons and generating magnon-magnon interactions. By synthesizing heterostructures based on bulk antiferromagnets, the team relies on interactions between spatially uniform antiferromagnetic magnons and short-wavelength ferromagnetic magnons to control the energy level spectrum in the sub-THz and THz regime. Conventional ferromagnetic resonance spectroscopy, spin-torque ferromagnetic resonance spectroscopy, and frequency-domain THz spectroscopy techniques are employed for the characterization of these samples.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.