Phase Competition in Complex Oxides by Design

Craig Fennie
ANL

The rational design of new materials with emergent properties is a challenge
today in materials physics. It begins with formulating a mechanism to
control the interplay between diverse microscopic degrees of freedom in
order to create targeted macroscopic phenomena and ends with the discovery
or design of new material realizations. When combined with first-principles
theoretical techniques, this approach provides an efficient strategy to
survey the vast space of possible materials to target for synthesis. As an
example, in this talk I will discuss recent work on designing materials
rarely found in nature - multiferroic oxides in which a spontaneous
magnetism not only coexists with but also is strongly coupled to a
spontaneous electric polarization. By manipulating the competition between
different ordered phases in real materials, I will show how in one case the
interplay between spins and phonons can be exploited to produce a colossal
magnetoelectric effect while in a second case, a polar lattice distortion
can be designed to induce ferromagnetism.