Origin of the Enhanced Polarization in La and Mg Co-substituted BiFeO3   Thin Film during the Fatigue Process
  We have studied the polarization fatigue of La and Mg co-substituted BiFeO3 thin film, where a polarization peak is observed during the fatigue process. The origin of such anomalous behavior is analyzed on the basis of the defect evolution using temperature-dependent impedance spectroscopy. It shows that the motion of oxygen vacancies (VO..) is associated with a lower energy barrier, accompanied by the injection of electrons into the film during the fatigue process. A qualitative model is proposed to explain the fatigue behavior, which involves the modification of the Schottky barrier upon the accumulation of VO.. at the metal-dielectric interface. 
Qingqing Ke, Amit Kumar, Xiaojie Lou, Kaiyang Zeng and John Wang
cond-mat.mtrl-sci