Frederiks transition theory

Experimental data confirm the main conclusion of the theory that near the sign reversal frequency of Ae there occurs the Frederiks transition. The observed modulated structure is static, and its threshold depends on neither the value of conductivity cr) nor its anisotropy experimentally measured threshold conditions... 

The most extensive theoretical and experimental studies of this problem have been done by Bocharov [76], who used an apparatus in which a SAW was excited at the substrate (1) (Fig. 7 a). The nematics was sandwiched between the glass plate (2) and the substrate (1) bearing transparent electrodes, to which an ac voltage (/ 50Hz) was applied. The dependence of the layer optical transmission m on the amplitude of the SAW with and without an applied electric field is shown in Fig. 9 b. The threshold value of the Frederiks transition was 4.65 V. It is evident that in the vicinity of this transition the sensitivity of the nematics to the action of the SAW increases by more than an order of magnitude. According to Vuzhva s theory, near the threshold of the Frederiks transition (E— Eq)... 

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