Atomic-level study of BiFe O3 under epitaxial strain

Abstract

Structural and thermal properties of BiFeO3 under compressive epitaxial strain are investigated using a shell model fitted to first-principles calculations. We show that a model developed for the bulk describes properly the behavior of the compound as function of the strain, including the appearance of tetragonallike phase with a large c/a ratio. The obtained temperature-strain phase diagram reproduces several features observed experimentally in thin films. Molecular dynamic simulations show that morphotropic phase boundary separating the R-like and T-like regions is temperature independent but with different phases along the transition region. The microscopic analysis of the temperature-strain phase diagram emphasizes the relevance of the interplay between polarization, oxygen octahedron rotations, and strain.