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

William Marsh Rice University, Houston TX

Investigators

Abstract

Non-Technical abstract Why 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 abstract This 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.