Materials by design - Ferroelectricity in Sr-Ti-O layered perovskites
Abstract: Transition metal oxides form a large family of compounds that host almost any physical property that exists in the solid state, such as (anti)ferromagnetism, piezoelectricity, or high-Tc superconductivity. Among these properties, ferroelectricity, i.e. spontaneous presence of a switchable, macroscopic electric dipole moment, holds great promise for technological applications as well as posing basic physical questions.
In this work (1), we study the transition to a novel (anti-)ferroelectric phase in Sr-Ti-O Ruddlesden-Popper compounds under strain, using ab initio computational methods (Density Functional Theory). In particular, we show that the information obtained from the phonon dispersions of the parent compound SrTiO3 can be used to elucidate new ways to experimentally drive these compounds to the vicinity of the ferroelectric phase transition where a large dielectric response is obtained. Our theoretical predictions are verified by experiments where films grown by oxide molecular beam epitaxy display not only large dielectric constants but also high figures of merit (2). This work proves the success of 'materials by design' approach where solid state physics and structural chemistry, aided by computational methods, are used to guide experiments to the discovery of new materials with desired properties and interesting physics.
1. T. Birol, N.A. Benedek, C.J. Fennie, "Interface control of emergent ferroic order in Ruddlesden-Popper Srn+1TinO3n+1", Phys. Rev. Lett. 107, 257602 (2011).
2. C.H. Lee, N.D. Orloff, T. Birol, et al., "Exploiting dimensionality and defect mitigation to create tunable microwave dielectrics", Nature 502, 532 (2013).