Strain Induced Metastable Phase and Phase Revolution in PbTiO₃-CoFe₂O₄ Nanocomposite Film

An inter-component epitaxial strain-induced PbTiO₃ metastable phase is observed in a PbTiO₃-CoFe₂O₄ epitaxial composite film, corresponding to the dielectric anomaly reported previously. High-resolution synchrotron radiation X-ray diffraction and first principles calculation demonstrate the coexistence of different PbTiO₃ phases, even a possible morphotropic phase boundary in the film, elucidating the underlying microscopic mechanism of the formation of PbTiO₃ metastable phase. This sheds light on the design and manipulation of electromechanical properties of epitaxial films, through the strain engineering.