Physics Lecture Today on Layered Ferroics

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Michael McGuire

The Department of Physics in the J. William Fulbright College of Arts and Sciences presents its Physics Colloquium, titled "Layered Ferroics: Structure and Magnetism in Functional van der Waals Bonded Compounds" by Michael A. McGuire of the Materials Science and Technology Division at Oak Ridge National Laboratory. The lecture will be from 4-5 p.m. Friday, Oct. 27, in PHYS 133. Refreshments will begin at 3:30 p.m. in PHYS 134.

The promise of new phenomena and functionalities is driving research efforts toward designer heterostructures built by stacking individual atomic layers of multiple materials with complementary properties. The top-down approach to producing the ultra-thin building blocks, mechanical exfoliation of layers from bulk single crystals, provides an exciting opportunity for collaboration among nanoscience researchers who study heterostructured devices and crystal growers who produce and study bulk materials.

McGuire will provide an overview of two classes of cleavable materials that they have recently grown and studied, which are of interest for this type of research. Both are composed of van der Waals bonded two-dimensional sheets and display ferroic order. After introducing the two material families and describing their crystal chemistry and basic physical properties, he will discuss in some detail magnetic order in chromium trihalides and ferrielectricity in copper-based thiophosphates.

Recent work with CrI3 has resulted in the first demonstration of a ferromagnetic monolayer cleaved from a bulk crystal, as well as integration of magnetism into van der Waals heterostructures. He will give an overview of recent progress on CrI3, CrCl3, and the isoelectronic 4d transition metal analogue MoCl3, which has a structural instability that masks inherently strong magnetism. Layered thiophosphates (e.g. CuInP2S6) include ferrielectric materials with transition temperatures that can exceed room temperature, and in which we have recently demonstrated in-plane heterostructure formation via chemical phase separation within a coherent crystalline framework.

Research is supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle LLC for the U.S. Department of Energy.