Direct Observation of the Critical Relaxation of Polarization Clusters in BaTiO3 Using a Pulsed X-Ray Laser Technique

We have developed a new method to investigate the relaxation time of the dipole moment in polarization clusters in BaTiO3. Time correlation of speckle intensities was measured by the use of a double pulsed soft x-ray laser. The evolution of the relaxation time of the dipole moment near the Curie temperature (T-C) was investigated. The maximum relaxation time (similar to 90 ps) is shown to appear at a temperature of 4.5 K above the T-C, being coincident with the one where the maximum polarization takes place. This method is widely applicable to any other critical decay processes at phase transitions.