Dielectric Relaxation and the Determination of the Sm A-Sm C* Phase Transition Temperature in DOBAMBC

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Abstract
The complex dielectric constant as a function of temperature and frequency has been measured in DOBAMBC close to the Sm A-Sm C* phase transition. The relaxation frequency and the dielectric strength of the Goldstone mode and soft mode were determined and the results are compared with the dielectric strength calculated using an extended Landau type of free-energy density proposed by Žekš. By analysing the experimental data carefully we are able to establish the Sm A-Sm C* phase transition temperature to be located a few degrees above the comparatively “broad” maximum exhibited by the dielectric strength. This location is also supported by our theoretical model.