Neutron scattering studies of magnetic order and spin dynamics in two-dimensional van der Waals magnetic materials

非技术摘要为什么你的手机会这么热？为什么电池从来不能维持足够长的时间？这是因为手机--以及笔记本电脑和电视等其他常见设备--需要通过金属片和晶体管发送电流才能通电，它们在这个过程中会产生被称为欧姆加热的热量。事实上，你的电池的大部分能量并没有用来让你上网：它正在产生浪费的热量。科学家们正在达到让这些晶体管变得更好的上限。但在一种材料上取得了进展，这种材料可能会让我们的设备变得更快，寿命更长：自旋电子设备。俗称“自旋电子”，这些材料是由绝缘体而不是金属制成的，因此不会产生欧姆加热。它们不是依靠电流，而是依靠电子的本征自旋--这意味着它们可以在不产生热量的情况下传输信息。这笔NSF拨款的目标是研究可能用作自旋电子学的材料。这项实验研究的目的是探索和了解被称为二维范德华材料的材料的磁性。为了做到这一点，我们将使用一种称为中子散射的过程。因为中子不带电荷，而是携带自旋，所以当它们对准一种材料时，它们的散射方式可以帮助我们理解它的磁性。实际上，这些实验将有助于进一步研究自旋电子学，并可能给电子设备行业带来革命性的变化。它们还可以提供对自然的更深层次的洞察：关于我们周围世界固有的磁性是如何基本工作的。该计划的广泛影响将包括培训研究生，特别是女性和代表性不足的少数民族，并在夏季接待本科生和高中生。技术摘要NSF项目是一项创新的实验计划，它将中子散射实验与基于实验室的材料工作相结合，旨在从根本上了解块状二维范德华(VDW)磁性材料的磁序和自旋动力学。该计划的目的是探索和了解二维VDW蜂窝和Kagomé晶格结构磁性材料各相中磁序和相互作用的微观起源。特别是，该团队将专注于CrI3、CrBr3、CrCl3、Cr(i、Br、Cl)3、Cr2Ge2Te6、α-RuCl3和YMn6Sn6的大块单晶。该程序包括三个部分：块状单晶合成、初始材料表征和中子散射。该计划的重点将是中子散射。在合成方面，PI建立了一个综合的材料实验室，可以生长所建议材料的单晶。这些单晶的初步表征将使用该小组的设施进行，包括现场单轴加压装置。中子散射将用于研究这些材料的磁序和自旋动力学性质。这些实验将在美国最好的设施中进行，包括橡树岭国家实验室(ORNL)的高通量同位素反应堆(HFIR)和散裂中子源(SNS)，以及NIST中子研究中心(NCNR)。此外，当美国没有类似的能力时，欧洲和日本的世界级中子散射设施也将被使用。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。

Non-Technical abstractWhy does your cell phone get so hot? And how come the battery never lasts long enough? It is because cell phones — and other common devices like laptops and TVs — need to send electric currents through pieces of metal and transistors to power on, and they produce heat, called Ohmic heating, in the process. In fact, most of your battery’s energy is not going toward getting you online: It is producing wasted heat. Scientists are now reaching a ceiling on making those transistors better. But there is progress on a material that might make our devices even faster and last longer: a spin electronic device. Colloquially called a “spintronic,” these materials are built out of insulators instead of metal, and as such, do not produce Ohmic heating. Instead of electric currents, they rely on the intrinsic spin of an electron — which means they could transmit information without generating heat. The goal of this NSF grant is to study materials that might work as spintronics. This experimental research aims to explore and understand the magnetic properties of the materials, which are called two-dimensional van der Waals materials. To do it, we will be using a process called neutron scattering. Because neutrons do not have a charge but carry spin, the way that they scatter when aimed at a material can help us understand its magnetic properties. Practically speaking, these experiments will help further the research around spintronics and could revolutionize the electronic device industry. They can also provide deeper insight into nature: about how the inherent magnetic properties of the world around us fundamentally work. Broad impacts of this program will include training of graduate students, particularly women and under-represented minorities, and hosting undergraduate and high school students during summer. Technical abstractThis NSF project is an innovative experimental program that integrates neutron scattering experiments with lab-based materials efforts, aimed at gaining a fundamental understanding of the magnetic order and spin dynamics in bulk two-dimensional (2D) van der Waals (vdW) magnetic materials. The objective of this program is to explore and understand the microscopic origin of magnetic order and interactions in various phases of 2D vdW honeycomb and Kagomé lattice structure magnetic materials. In particular, the team will focus on bulk single crystals of CrI3, CrBr3, CrCl3, Cr(I,Br,Cl)3, Cr2Ge2Te6, alpha-RuCl3, and YMn6Sn6. The program has three components: bulk single crystal synthesis, initial materials characterization, and neutron scattering. The focus of the program will be on neutron scattering. For synthesis, the PI has established a comprehensive materials laboratory and can grow single crystals of the proposed materials. The initial characterization of these single crystals will be performed using facilities in the group, including an in-situ uniaxial pressure device. Neutron scattering will be used to study the magnetic order and spin dynamical properties of these materials. These experiments will be performed at the best facilities in the US, including the high-flux isotope reactor (HFIR) and the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL), and the NIST Center for Neutron Research (NCNR). In addition, world-class neutron scattering facilities in Europe and Japan will also be utilized when similar capabilities are unavailable in the US.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.