Two different types of hysteresis in dielectric property of ferroelectric liquid crystal

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Abstract
We have measured the field intensity dependence of D–E hysteresis in the ferroelectric liquid crystal DOBAMBC using Pepinsky bridge and also visually observed domain of smectic C* phase under ac field. Two different types of hysteresis are observed, one of which is ordinary D–E loop obtained under applying ac field and another is P r-⟨E⟩loop where P r is the residual polarization and ⟨E⟩the effective field amplitude. The stroboscopic observation synchronized with the applied field with a certain time delay has been done in order to understand the mechanism. The cause of the former hysteresis is unknown but at least does not seem to be directly associated with motion of helicoidal structure. The latter is caused by pinning of motion of the helicoidal structure and by the first order structural transition between helicoidal and nonhelicoidal smectic C* induced by the applied electric field.