Unusual phenomena in compositionally modulated BST systems

Artificial BST based superlattices are potential candidates for applications such as storage capacitors and dielectrics for the next generation dynamic random access memories and tunable microwave devices. Using first-principles-based Monte-Carlo and Molecular Dynamics simulations using effective Hamiltonians, we predict the temperature-versus-misfit strain phase diagram, domain evolution, and dielectric response in these systems. Our studies reveal an unusually complex phase diagram involving novel nanodomain phases with anomalous microstructures. The microscopic origins of these anomalous behaviors and their manifestations in the static and dynamic dielectric response will be discussed. This talk will also present results obtained using first principles density functional calculations and inelastic neutron scattering measurements of PbTiO3, BaTiO3 and SrTiO3 carried out at the ILL, Oak Ridge National Lab., and the Intense Pulsed Neutron Source.