Electric dipole sheets inBaTiO3/BaZrO3superlattices

Abstract

We investigate two-dimensional electric dipole sheets in the superlattice made of BaTiO 3 and BaZrO 3 using first-principles-based Monte-Carlo simulations and density functional calculations. Electric dipole domains and complex patterns are observed and complex dipole structures with various symmetries (e.g. P ma2, Cmcm and P mc2 1 ) are further confirmed by density functional calculations, which are found to be almost degenerate in energy with the ferroelectric ground state of the Amm2 symmetry, therefore strongly resembling magnetic sheets. More complex dipole patterns, including vortices and anti-vortices, are also observed, which may constitute the intermediate states that overcome the high energy barrier of different polarization orientations previously predicted by Lebedev [1]. We also show that such system possesses large electrostrictive effects that may be technologically important.

Dielectric response of BaZrO3/BaTiO3 superlattice

“…In addition, ðÞ, has a large dispersion over temperature between 200 and 600 K. Furthermore, the sudden change in susceptibility at $200 K also indicates a phase transition, consistent with the partially antiferroelectric phase we have seen in previous work. 32 The flat susceptibility below $200 K in Fig. 3(a) is likely a feature of antiferroelectric phase.…”

“…As previous studies have shown, the BZO/BTO superlattice has a phase transition at T C ' 220 K. Below T C , dipoles in the x-y planes become partially correlated and the dipole configuration partially antiferroelectric. 32 The resonances in Figs. 2(d) and 2(e) are characteristics of such an antiferroelectric phase.…”

“…32 The setup of such BZT system and its static properties had been investigated in Ref. 32. After obtaining the dielectric response of ordered BZO/BTO superlattice, we will be able to understand how order/disorder of ions affect the formation of relaxors.…”

“…Our approach is to simulate a BaZrO 3 / BaTiO 3 1:1 superlattice, grown along the ½001 direction, where the chemical environment for each Ti ion is uniform. 32 The setup of such BZT system and its static properties had been investigated in Ref. 32.…”

“…The broad peak is likely because the weak correlation between the in-plane dipoles (Ti ions). 32 Furthermore, both the total and Ti dielectric response [ Figs. 1(d) and 1(e)] show signatures of a low-frequency ( .100 cm À1 ) relaxation.…”