Landau theory of phase transition in ferroelectric vinylidene fluoride/trifluoroethylene copolymer single crystals: Hysteresis loop

Ferroelectric hysteresis loops in vinylidene fluoride/trifluoroethylene, P[VDF/TrFE], copolymer single crystals are discussed on the basis of the Landau-type free energy function with the anisotropy parameter γ2. It was found that the coercive field strongly depends on the value of γ2. and decreases as γ2 = 0 is approached, because the Landau-type free energy function becomes isotropic in the order parameter space. We successfully reproduced the p-E hysteresis loop with a square shape and a small coercive field in P[VDF/TrFE] on the basis of the Landau theory with the anisotropy parameter γ2. © 2005 The Japan Society of Applied Physics.