Dynamic Multiscale Model for Dielectric Anomaly in PbTiO₃-CoFe₂O₄ Epitaxial Nanocomposite Film

Theoretical calculations based on a multiscale model are proposed to interpret the dielectric anomalous enhancement observed around x=0.2 in the (PbTiO₃)_1?x-(CoFe₂O₄)_x (0≤x≤1) epitaxial nanocomposite spread film. First principles calculation combined with thermodynamics statistics reveals that the dynamic ratio between different PbTiO₃ phases under an external electric field is responsible for the dielectric anomaly. To verify this model with direct microstructure evidence, high resolution and high accuracy synchrotron radiation x-ray diffraction of (PbTiO₃)_0.8-(CoFe₂O₄)_0.2 epitaxial composite film under an in situ electric field is collected, in which an obvious modulation of the phase balance of PbTiO₃ is observed.