Abstract
We have fabricated superlattices with ultrathin layers. Because of the superlattice geometry, the samples show a large anisotropy in their electrical resistivity, which can be controlled by changing the thickness of the layers. Therefore, along the ferroelectric direction, layers can act as dielectric, rather than metallic, elements. We show that, by reducing the concentration of , an increasingly important effect of polarization asymmetry due to compositional inversion symmetry breaking occurs. The results are significant as they represent a new class of ferroelectric superlattices, with a rich and complex phase diagram. By expanding our set of materials we are able to introduce new behaviors that can only occur when one of the materials is not a perovskite titanate. Here, compositional inversion symmetry breaking in bicolor superlattices, due to the combined variation of and site ions within the superlattice, is demonstrated using a combination of experimental measurements and first principles density functional theory.
- Received 13 January 2012
DOI:https://doi.org/10.1103/PhysRevLett.109.067601
© 2012 American Physical Society