Evolution of phase domains in relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃

Pb(Mg_1/3Nb_2/3)O₃ or PMN is a relaxor perovskite that exhibits a giant dielectric response to the electric field over a broad temperature range with a frequency-dependent peak in dielectric permittivity.  Such behavior, despite the intense debate of its origin, is believed to be strongly correlated to the phase domains, whose dynamics can be probed as the material is under external electrical stimuli. In this talk, we will present our recent study of wide-angle x-ray photon coherent spectroscopy (XPCS) on a PMN bulk crystal at the Advanced Photon Source. Using oscillating electric fields as the external stimuli, we observed strong responses of speckle patterns along different directions near the (0 0 2) Bragg peak. The two-time correlation displayed a periodic pattern with detailed structures and phase shifts, which will be explained by a phenomenological model. The speckle analysis in this work will provide a new dynamical view of the coupling between phase domains and electric fields in this material.