Polar fluctuations of nanoscale size as a source of giant dielectric response of relaxor ferroelectrics

Characteristic frequencies of nanoscale polar fluctuations have been resolved by means of neutron diffuse scattering measurements on a Sr_0.61Ba_0.39Nb₂O₆ single crystal in the MHz-GHz frequency region.

Comparison with dielectric measurements proved that these polar fluctuations are a source of giant dielectric response, whose temperature-frequency dependence is specific for a significant group of substances exhibiting a glass-type ferroelectric phase transition, so-called relaxor ferroelectrics [ P. Ondrejkovic et al., Phys. Rev. Lett. 113, 167601 (2014)].

Figure: (a) Typical domain structure with polar nanodomains and (b) its characteristic disk-like diffuse scattering. Comparison of temperature dependence of diffuse scattering intensity obtained (c) experimentally on neutron spectrometers at Institut Laue-Langevin (Grenoble) and (d) numerically from a model based on dielectric data at various energy transfers.