The dynamics of a Sm-${\mathit{C}}^{\mathrm{*}}$ director field in an ac electric field has been studied by means of light scattering. Scattering of resonance type has been observed by variation of field frequency at fixed temperatures. The resonance scattering is suppressed in high electric fields, at low temperatures in the Sm-${\mathit{C}}^{\mathrm{*}}$ phase, and in films thinner than a threshold value ${\mathit{N}}_0$. A theory of director switching is proposed that consistently describes the observed anomalies. The film parameters viscosity, dielectric anisotropy, and polar film anisotropy are determined. This work provides evidence that the Sm-${\mathit{C}}^{\mathrm{*}}$ structure in the boundary layers and the thin films of materials with high spontaneous polarization correspond to the weak anisotropic state predicted early. (c) 1995 The American Physical Society

• Received 28 July 1995

DOI:https://doi.org/10.1103/PhysRevE.52.6250