Permittivity and refraction index of ferroelectric in intensive external field

The behaviour of a ferroelectric in an intensive external electro-magnetic field is discussed. It is shown that, in fields with the amplitude E 0 > 10 5 V/cm, the phase transition temperature becomes higher, the static permittivity and Curie-Weiss constant increase. The optical absorption coefficient decrease changes to its increase. There is a threshold field, passing by which the system divides into layers of periodical structure of para-and ferroelectric phases. A difference for damping and refraction index was studied, while the field propagation was directed along and against the spontaneous polarization vector.