Materials Science - Physical Properties of Materials: Coupling Magnetic, Electric and Elastic Responses in Two Dimensional Atomic Layers
Abstract
The recently developed ability to isolate single sheets of two-dimensional van der Waals (2D VDW) materials has motivated intense research into stacking different atomic layers to assemble devices or induce novel properties. While many of the functional properties found in three-dimensional materials are seen in bulk layered materials, single sheets of these materials that individually display ferromagnetism, ferroelectricity and piezoelectricity vary from exceedingly rare to non-existent, and no single sheets are known to combine these properties. Such a single sheet multiferroic offers promise to overcome materials and interfacial issues that have complicated development of multiferroic-based microwave and radio frequency signal processors, highly sensitive magnetic field sensors and spintronic devices. Therefore, a combined theoretical and experimental effort will be undertaken with the long-term goal of creating stable, transferable atomic layers that couple magnetic, electrostatic and elastic responses such that a change in the strength of an externally applied field (magnetic, electric, or stress) in one of these properties triggers a change of the strength of the other two. The search space for such layers will be expanded to structures that are uniquely stable as single 2D VDW layers due to surface and interfacial energy minimization. The focus is on environmentally stable oxides that ultimately can be readily processable. The approach closely couples theory and experiment following a closed feedback loop materials design paradigm. First principles theory identifies promising materials that are then grown by molecular beam epitaxy and characterized down to the atomic level using scanning probe microscopy (SPM) in conjunction with surface diffraction and microscopy. The magnetic properties of the single 2D layers are characterized through measurements of magneto-optical Kerr effect (MOKE) and spectroscopically using x-ray dichroism measurements. The coupling between the magnetic, electrostatic and elastic responses is determined via advanced SPM methods and MOKE measurements as the layers are deformed. Comparison of experimental results with theoretical predictions provides the feedback to understand the experimental observations and refine the theory as necessary, with theoretical developments offering guidance on how to form desired structures and on modifications necessary to achieve the desired properties. The starting point for the project is first row transition metal silicates and phosphates that either have been observed in 2D form or have potential to form 2D VDW layers, display structural moieties with favorable magnetic couplings, and display the asymmetries essential to display piezoelectricity.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 17, 2019
- Source ID
- W911NF1910371
Entities
People
- Eric Altman
Organizations
- Army Contracting Command
- United States Army
- Yale University