EAGER/Collaborative Research: CRYO: Engineering Atomically Thin Magnetic Materials for Efficient Solid-State Cooling at Cryogenic Temperatures

固态冷却方案可以潜在地避免在1K以下的低温制冷中使用日益昂贵和稀缺的He3。目前几乎所有用于量子计算机、传感器和其他新技术运行的商用超低制冷方法都需要He3。这个探索性研究（EAGER）项目将推进对超薄磁性材料热释放过程的基本理解，从而为下一代固态制冷磁性量子材料的制造提供指导，促进纳米尺度上热传输和冷却的基础物理学，并帮助开发新型冷却技术。当某些磁性材料在低温下磁化时，磁场的去除会导致材料内部曾经有序的磁畴的随机化。在这些多磁畴的形成或排序过程中，材料中的热能被磁畴吸收以重新定向其磁化，从而导致温度下降（即冷却）。原子薄的磁性材料可以用来控制和增强这些过程，因此可以为新兴的冷却设备开辟未知的机会。这项工作将支持基础研究，以了解对这些磁性量子材料的修改，以实现高效的固态冷却，特别是在低于1K的低温下。这项有待开发的技术可以缓解目前与全球氦气短缺有关的挑战。高中学生和传统上代表性不足的群体的学生将接触到包括量子材料制造，材料建模和模拟，低温硬件工程和低温实验的综合训练。这项研究将有助于为这些学生提供必要的知识和专业知识，作为未来量子科学和工程的劳动力。磁热效应在固态制冷方面具有很大的潜力。然而，传统材料中的磁热效应并不强，但如果结构相变与磁相变同时发生，则可以增强磁热效应。然而，诱导这些一阶相变通常依赖于通过稀有和昂贵的稀土元素基化合物对材料的成分进行改性。本研究旨在克服二维磁性材料在理解和控制方面的知识差距，以增强磁热效应。研究小组将应用第一性原理材料模拟来理解二维磁体中的磁性结构关系，采用实验合成和加工来设计二维磁体，并应用磁电和磁光表征来量化所得到的磁性。该研究将阐明新兴二维磁体的局部原子结构、晶体结构与磁性能之间的基本关系，为清洁冷却技术低维磁性结构的设计和优化提供有益的指导。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。

Solid-state cooling schemes can potentially circumvent the use of increasingly expensive and scarce He3 in cryogenic refrigeration below 1K. He3 is required in almost all current commercial ultralow refrigeration approaches used in the operation of quantum computers, sensors and other new technologies. This EArly-concept Grant for Exploratory Research (EAGER) project will advance the fundamental understanding of the heat-release process in ultrathin magnetic materials and thus provide the guidance to manufacture magnetic quantum materials for next-generation solid-state refrigeration, promoting the fundamental physics of heat transport and cooling on the nanoscale and aid in the development of new classes of cooling technologies. When certain magnetic materials are magnetized at low temperatures, the removal of the magnetic field leads to the randomization of once magnetically ordered domains within material. During the formation or ordering of these of multiple magnetic domains, thermal energy in the material is absorbed by domains to reorient their magnetizations, thereby leading to temperature drop (i.e., cooling). Atomically thin magnetic materials can be engineered to control and enhance these processes and thus could open up unexplored opportunities for emerging cooling devices. This effort will support the fundamental research to understand the modifications to these magnetic quantum materials to enable efficient solid-state cooling, particularly at cryogenic temperatures such as below 1K. The technology to be developed can mitigate the existing challenges associated with the worldwide shortage of helium. High-school students and students of traditionally underrepresented groups will be exposed to the comprehensive training including quantum materials fabrication, materials modelling and simulation, cryogenic hardware engineering, and low-temperature experiments. This research will help to equip these students with necessary knowledge and expertise as the workforce for the future quantum science and engineering.The magnetocaloric effect holds a great potential for solid-state refrigeration. However, the magnetocaloric effect in traditional materials is not strong, but it can be enhanced if a structural phase change can be concomitant with the magnetic phase transition. However, inducing these first-order phase transitions have conventionally relied on the compositional modification of the material through scarce and expensive rare-earth-elements based compounds. This research proposes to overcome the knowledge gap in the understanding and control of two-dimensional magnetic materials for an enhanced magnetocaloric effect. The research team will apply first-principles materials simulations to understand the magnetism-structure relationship in two-dimensional magnets, employ experimental synthesis and processing to engineer two-dimensional magnets, and apply magnetoelectric and magneto-optical characterizations to quantify the resultant magnetic properties. The research will elucidate the fundamental relationship between local atomic structures, crystalline structures and magnetic properties of emerging two-dimensional magnets, which could provide useful guidance for the design and optimization of low-dimensional magnetic structures for clean cooling technologies.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.