Optical probe,local fields,and Lorentz factor in ferroelectrics |
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Authors: | L M Blinov V V Lazarev S P Palto S G Yudin |
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Institution: | 1. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 119333, Russia
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Abstract: | An optical probe is suggested that allows measurements of the local field and Lorentz factor (L) in ferroelectric medium. The copolymer poly (vinylidene fluoride/trifluoroethylene) is mixed with Pd-tetraphenylporphyrin (TPP-Pd) that has a very narrow absorption band. Thus, TPP-Pd serves as a molecular optical probe of the local field. During the switching of the electric field lower than the coercive one the factor L of an unpolarized ferroelectric mixture is found to be of about 1/3 that corresponds to the random distribution of molecular dipoles in the ferroelectric. With increasing field, the dipole orientation acquires a lower symmetry and L tends to zero as predicted by lattice sum calculations for vinylidene fluoride. The knowledge of the field dependence of L and the usage of the optical probe makes it possible to measure directly the local and macroscopic fields in the individual elements of various ferroelectric-dielectric heterostructures. |
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