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

为什么你的手机变热了？为什么电池的续航时间总是不够长？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来通电，在这个过程中它们会产生热量，称为欧姆加热。事实上，电池的大部分能量并不是用来上网的：它产生的是废热。科学家们在改进晶体管方面已经达到了极限。但有一种材料取得了进展，这种材料可能会使我们的设备更快、更耐用：一种自旋电子设备。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。它们依靠的不是电流，而是电子的固有自旋——这意味着它们可以在不产生热量的情况下传输信息。这项NSF拨款的目标是研究可能作为自旋电子学工作的材料。本实验研究旨在探索和了解二维范德华材料的磁性能。为了做到这一点，我们将使用一个叫做中子散射的过程。因为中子不带电荷，但携带自旋，所以当它们瞄准一种物质时散射的方式可以帮助我们了解它的磁性。实际上，这些实验将有助于进一步围绕自旋电子学的研究，并可能彻底改变电子设备工业。它们还可以提供对自然的更深入的了解：关于我们周围世界固有的磁性是如何从根本上工作的。该项目的广泛影响将包括培训研究生，特别是女性和少数族裔，并在夏季接待本科生和高中生。技术摘要：本NSF项目是一个创新的实验项目，将中子散射实验与实验室材料工作相结合，旨在获得对块状二维范德华磁性材料的磁序和自旋动力学的基本理解。本项目的目的是探索和理解二维vdW蜂窝和kagom<s:1>晶格结构磁性材料的磁序和各相相互作用的微观起源。该团队将特别关注CrI3， CrBr3, CrCl3, Cr(I,Br,Cl)3, Cr2Ge2Te6， α - rucl3和YMn6Sn6的块状单晶。该程序有三个组成部分：体单晶合成，初始材料表征和中子散射。这个项目的重点是中子散射。在合成方面，PI已经建立了一个综合材料实验室，可以生长所提出材料的单晶。这些单晶的初步表征将使用小组的设备进行，包括原位单轴压力装置。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，如果美国没有类似的能力，欧洲和日本的世界级中子散射设施也将得到利用。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。

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.