Optical probe, local fields, and Lorentz factor in ferroelectrics
L. M. Blinov, V. V. Lazarev, S. P. Palto, S. G. Yudin
Shubnikov Institute of Crystallography of the RAS, 119333 Moscow, Russia
Abstract
An optical probe is suggested that allows measurements of the local
field and Lorentz factor (L)
in ferroelectric medium. The copolymer poly (vinyliden
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 a non-polarized 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 vinyliden-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.