Abstract
Macroscopic ferroelectric polarization switching, similar to other first order phase transitions, is controlled by nucleation centers. Despite 50 years of extensive theoretical and experimental effort, the microstructural origins of the Landauer paradox, i.e. the experimentally observed low values of coercive fields in ferroelectrics corresponding to implausibly large nucleation activation energies, are still a mystery. In this letter, we develop an approach to visualize the nucleation centers controlling polarization switching processes with nanometer resolution, determine their spatial and energy distribution, and correlate them to local microstructure. The random bond and random field components of the disorder potential are extracted from positive and negative nucleation biases. Observation of enhanced nucleation activity at the 90� domain wall boundaries and intersections combined with phase-field modeling identifies them as a class of nucleation centers that control switching in structural-defect free materials.
