Probing the role of single defects on the thermodynamics of electric-field induced phase transitions

The kinetics and thermodynamics of first order transitions are universally controlled by defects that act as nucleation sites and pinning centers. Here we demonstrate that defect-domain interactions during polarization reversal processes in ferroelectric materials result in a pronounced fine structure in electromechanical hysteresis loops. Spatially resolved imaging of a single defect center in multiferroic BiFeO3 thin film is achieved, and the defect size and built-in field are determined self-consistently from the single-point spectroscopic measurements and spatially resolved images. This methodology is universal and can be applied to other reversible bias-induced transitions including electrochemical reactions. © 2008 The American Physical Society.