Picosecond View Of Microscopic-Scale Polarization Clusters In Paraelectric Batio3

The polarization clusters existing in both the ferroelectric and the paraelectric phase of BaTiO3 are directly observed and characterized for the first time by a picosecond soft x-ray laser speckle technique. These dynamic clusters appear continuously across the Curie temperature T-c. The clusters' distance increases approximately linearly with temperature, while their mean size does not change significantly. The polarization exhibits a maximum at a temperature about 5 degreesC above T-c. The clusters' short-range correlation strength diverges as (T-T-c)(-0.41+/-0.02) as temperature decreases toward T-c.