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.