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Layered Ferromagnetic and Ferrielectric Materials

Michael A. McGuire, MSTD devision, Oak Ridge National Laboratory
Friday, September 30, 2016 - 3:00pm to 4:00pm
PAT C-520

The promise of new
phenomena and functionalities is driving research efforts toward designer
heterostructures built by stacking 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. I will provide an overview of two classes of
materials that we have recently grown and studied, transition metal halides and
transition metal thiophosphates, which are of interest for this type of
research. Both are composed of easily cleavable, van der Waals bonded layers
and display ferroic order. After introducing the two material families and
describing their crystal chemistry and basic physical properties, I will
discuss in some detail ferromagnetism in chromium trihalides and ferrielectricity
in copper-based thiophosphates. Chromium trihalides (CrCl
3, CrBr3,
and CrI
3) are Mott insulators that undergo crystallographic phase
transitions and order magnetically at low temperature. Layered thiophosphates
(e.g. CuInP
2S6) include antiferroelectric and
ferrielectric materials with transition temperatures that can exceed room
temperature, and in which we have recently demonstrated
heterostructure formation via chemical phase separation.​