Phase Transitions in Epitaxial (−110)BiFeO3Films from First Principles

Abstract

The effect of misfit strain on properties of epitaxial BiFeO3 films that are grown along the pseudocubic [110] direction, rather than along the usual [001] direction, is predicted from density-functional theory. These films adopt the monoclinic Cc space group for compressive misfit strains smaller in magnitude than ≃1.6% and for any investigated tensile strain. In this Cc phase, both polarization and the axis about which antiphase oxygen octahedra tilt rotate within the epitaxial plane as the strain varies. Surprisingly and unlike in (001) films, for compressive strain larger in magnitude than ≃1.6%, the polarization vanishes and two orthorhombic phases of Pnma and P2(1)2(1)2(1) symmetry successively emerge via strain-induced transitions. The Pnma-to-P2(1)2(1)2(1) transition is a rare example of a so-called pure gyrotropic phase transition, and the P2(1)2(1)2(1) phase exhibits original interpenetrated arrays of ferroelectric vortices and antivortices.

Natural optical activity and its control by electric field in electrotoroidic systems

“…(27), (32), and (23)). An example of the latter can be found in Reference 23 , where a pure gyrotropic phase transition leading to a piezoelectric, but non-polar, P 2 1 2 1 2 1 state (that exhibits spontaneous electrical toroidal moments) was discovered in a perovskite film. Next, we describe the theoretical prediction of a material where the former scenario is realized.…”

Properties of epitaxial (110) BaTiO3films from first principles

“…For instance, the (fundamentally-and technologically-important) temperature-versus-misfit strain diagram has never been revealed for any ferroelectric film grown along the [110] direction, to the best of our knowledge, despite the fact that (110) FE films have been experimentally realized [15][16][17] and that this special growth direction has been recently shown to generate unusual phenomena. 18 The general aim of this paper is to address such issue by performing simulations on epitaxial (110) BTO films. Novel features are predicted to occur in these films.…”

Epitaxial short-period PbTiO3/BiFeO3superlattices studied by first-principles calculations

“…Other examples include a photovoltaic effect 5,6 , an anomalous dependency of critical temperatures with misfit strain 7 and the nearly simultaneous occurrence of a ferroelectric and a magnetic transition near room temperature 8,9 in (001) BFO films. Interpenetrated arrays of vortices and antivortices resulting from a pure gyrotropic phase transition have also been predicted to occur in epitaxial (110) BiFeO 3 systems 10 .…”