James Rondinelli of the Department of Materials Science and Engineering at Drexel University will present on Wednesday, October 9, 2013, as part of our Fall Seminar Series. The seminar will take place at 3:00pm in Maryland Hall 110. Graduate students are required to attend. The seminar abstract is provided below.
Disruptive Design Strategies for Emergent Ferroelectricity
There are two main routes to accelerate materials discoveries for advanced electronic and sustainable energy technologies: serendipitous realization through conventional synthesis or computationally guided growth of novel materials through, e.g., artificial structuring of bulk compounds at the atomic scale. Recently, the launch of the Materials Genome Initiative (MGI) at the national level has reinvigorated the search for new routes to accelerate the discovery of advanced materials for rapid deployment—the aim being to evolve a “hunter and gatherer” discovery paradigm into the cultivation of materials by design.
Within this setting, and motivated by prospects of integrating perovskite-structured oxides into electronic devices to reduce consumer power consumption, I describe in this talk the design methodology and theoretical discovery of a new class of “rotation-induced” ferroelectric materials. Such materials exhibit a spontaneous and switchable electric polarization that can be used for logic and data storage. Bottom-up engineering of the atomic framework structure, specifically rotations of transition metal octahedra at the unit cell level, is applied to realize ferroelectricity in artificial ABO3-structured composites formed by interleaving two bulk materials with no tendency to such behavior. This emergent, chemistry-independent, form of ferroelectricity – octahedral rotation-induced ferroelectricity – offers a reliable means to externally address and achieve deterministic electric-field control over magnetism. I discuss the required crystal-chemistry criteria, which are obtained from a combination of group theoretical methods and electronic-structure computations, to select the compositions and stoichiometries giving polarizations comparable to the best known ferroelectric oxides. I then show how the approach is readily translated to AnBnO3n+1 (n=1 or 2) Ruddlesden-Popper (RP) oxides with disconnected layers of corner-sharing octahedra to design improper multiferroism in a class of manganites using (pseudo)-rotations that describe Jahn-Teller distortions. I conclude by suggesting new materials families to search for unconventional forms of ferroic (or anti-ferroic) behavior, and more broadly how this general approach of physical properties by atomistic structure design within the MGI is immediately amenable to other material functionalities.