Coupled director and polarization fluctuations in suspensions of ferroelectric nanoparticles in nematic liquid crystals.

In colloidal suspensions of nanosized ferroelectric particles and nematic liquid crystals a large increase in the isotropic-nematic transition temperature has been observed recently. By dynamic light scattering we measured the relaxation rate of the nematic director fluctuations in colloidal systems with BaTiO3 and Sn2P2S6 particles. A substantial increase in the bend-mode relaxation rate, attributed to an increase in the bend elastic constant, is observed. A mode with relaxation rate around 200000 s(-1), independent of the scattering vector, is also observed. We propose that it represents the out-of-phase motion of the nematic director and average direction of the spontaneous polarization of the ferroelectric particles. No translation motion is observed, indicating that the particles may form chains.