NYCCS/Physics Seminar

Functional oxides, characterized by high sensitivity to applied fields and stresses, are of great current interest both for their fundamental physics and for technological applications including transducers, energy conversion, and information storage. In perovskite oxides, layered perovskites and other complex-structured oxide families, a wide variety of distorted equilibrium phases can be produced by the freezing-in of one or more lattice instabilities of an appropriate high-symmetry reference structure. In this talk, I discuss how the information from computational first-principles studies of these systems provides guidance for altering the balance of the competition of instabilities of different character under conditions characteristic of epitaxial thin films, superlattices, and nanoparticles, leading to the realization of novel phases with structure and properties different from those of the bulk equilibrium phase, as well as desirable functional behavior near the phase boundaries. Examples presented will include the observation of epitaxial-strain-induced ferroelectricity in perovskite titanates and manganates, with discussion of the additional possibility of multiferroism and magnetoelectric coupling in magnetic oxide systems.