Building in material properties layer by layer Matthew Dawber , SUNY at Stony Brook, DMR 1055413

1. Building in material properties layer by layerMatthew Dawber, SUNY at Stony Brook, DMR 1055413 In a combined experiment and theory effort, researchers at Stony Brook University in New York have shown that by a novel choice of materials artificially layered structures can be built with a preferred polarization direction. These materials could have applications as self-poled piezoelectrics, for use in electromechanical devices, or highly coupled multiferroics, for advanced computer memory applications. By depositing very fine layers of two different materials one on top of each other, each only a few atoms in thickness, the researchers made a new material, called a superlattice. By this approach it is possible to introduce new properties that can be significantly different than either of the materials used. Here a ferroelectric material, lead titanate, was used in combination with a material that is normally metallic, strontium ruthenate. However, as the strontium ruthenate layers are very thin, the conductivity in the new artificial material is very low in the direction of the ferroelectric polarization. The new material thus behaves like a ferroelectric, but one that has a strong preference for one polarization direction over another. This effect is driven by a breaking of symmetry across the interfaces of the material. In addition to the polarization effect, the symmetry breaking achieved also has the potential to allow coupling between ferroelectricity and magnetism, which is the highly desired property of multiferroic materials. The researcher’s findings will be published in Physical Review Letters in August 2012. Top: The two lead graduate students behind the discovery, left, Sara Callori, from the experimental group of Prof. Matthew Dawber, right, Judith Gabel from the theory group of Prof. Marivi Fernandez Serra. Bottom: A schematic of an interface in a superlattice showing how changing just one layer of atoms can break symmetry. The researchers found this could have very interesting effects on the properties of the material.