Probing novel phases of matter in van der Waals magnet Fe5-xGeTe2

Auburn University, Auburn AL

Investigators

Abstract

Nontechnical abstract Van der Waals materials have atomically thin layers that are vertically stacked and have weak interlayer bonds. Graphite is one example. They can be fabricated into two-dimensional forms, which are of tremendous interest for the next generation nanometer-scale electronics. Recently, intrinsic magnetic order was demonstrated in two-dimensional van der Waals materials opening up new opportunities in data storage and information processing. Van der Waals magnetic materials are also of interest in fundamental condensed matter physics, because they possess appreciable interactions between the crystal structure, electronic states, and magnetic order that could lead to novel phases of matter with unique properties. This project will establish the relationships between the structural, electronic, and magnetic properties of a new van der Waals magnetic material with a high magnetic transition temperature and complex magnetic order. Understanding these properties will help in the design of high-efficiency electronic devices. The research goals are accomplished through comprehensive investigations combining multiple state-of-the-art experimental techniques. The research activities involve collaboration with scientists from different disciplines, which provides extensive training for graduate and undergraduate students at Auburn University. The experiments to be carried out at the national laboratories will promote the students’ professional development. The principal investigators will integrate the research topics into two existing courses and will continue to participate in the K-12 education under established local outreach programs. Technical abstract Recently, Fe5–xGeTe2 emerges as a new member in van der Waals magnetic materials with high Curie temperature and good stability in ambient conditions. Remarkably, in this compound, the complex atomic structure, together with the distinct electronic states and spin moments on the nonequivalent Fe sites can strongly impact the magnetic order. In this project, the interplay between the crystal structure, electronic states, and magnetic order will be investigated, to develop an in-depth understanding of the novel phases of matter in Fe5–xGeTe2. Specifically, this project consists of three intercrossing objectives: 1) elucidate the connection between crystal structure and magnetism; 2) reveal the interplay of electronic states and magnetic order; and 3) realize electric control of magnetization in Fe5–xGeTe2-based van der Waals heterostructures. The research team employs a unique toolset combining nonlinear optics, synchrotron-based photoemission spectroscopy/microscopy, and electro- and magnetic-transport techniques to identify the properties of this compound. Our findings will lead to the fundamental understanding of the interactions between lattice, charge, orbital, and spin degrees of freedom in two-dimensional quantum materials and open up new avenues in designing spintronic devices. This grant promotes the interdisciplinary research effort at Auburn University and the long-term collaboration between Auburn University and national laboratories. This project is jointly funded by the Electronic and Photonic Materials program in the Division of Materials Research and the Established Program to Stimulate Competitive Research (EPSCoR). 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.