Wolter Siemons

Temperature-Driven Structural Phase Transition in Tetragonal-Like BiFeO₃

Highly strained BiFeO₃ exhibits a ''tetragonal-like, monoclinic'' crystal structure found only in epitaxial films (with an out-of-plane lattice parameter exceeding the in-plane value by >20%). Previous work has shown that this phase is properly described as an M_C monoclinic structure at room temperature [with a (010)_pc symmetry plane, which contains the ferroelectric polarization]. Here, we show detailed temperature-dependent X-ray diffraction data that reveal a structural phase transition at ~100 ^oC to a high-temperature M_A phase [''tetragonal-like'' but with a (110)_pc symmetry plane]. These results indicate that the ferroelectric properties and domain structures of the strained BiFeO₃ are strongly temperature dependent.