Epitaxial Pb(Zr,Ti)O3 ultrathin films under open-circuit electrical boundary conditions.

The temperature-versus-misfit-strain phase diagram of Pb(Zr,Ti)O3 ultrathin films under open-circuit electrical boundary conditions is simulated via the use of an effective Hamiltonian. Two novel phases, both exhibiting dipolar nanodomains and oxygen octahedral tilting, are discovered. The interplay between dipolar, antiferrodistortive, alloying, and strain degrees of freedom induces several striking features in these two phases, such as the chemical pinning of domain walls, the enhancement of oxygen octahedral tilting near the domain walls, and the existence of dipolar waves and cylindrical dipolar chiral bubbles.

Chiral patterns of tilting of oxygen octahedra in zero-dimensional ferroelectrics and multiferroics: a first principle-based study.

First-principles-based Monte Carlo approaches are developed to investigate finite-temperature properties of stress-free nanodots made of the ferroelectric Pb(Zr,Ti)O3 system and of the multiferroic BiFeO3 compound. These zero-dimensional materials both exhibit various, novel chiral patterns for the tilting of the oxygen octahedra. Such exotic patterns originate from the coupling between the tiltings of the oxygen octahedra and the electric dipole vortices, and require original order parameters to quantify them.