A spontaneous dipole moment in a ferroelectric can be reoriented by applying an external electric field. The presence of hysteresis in the P(E) dependence is the reason why this sort of material was given the name of ferroelectrics, by analogy with ferromagnetics. Typical members of this family of compounds are barium titanate (BaTiO₃) and lithium niobate (LiNbO₃). The most distinctive features of ferroelectrics are their extremely high dielectric permittivity and very strong dependence on temperature and electric field, which forms the basis for the widespread use of ferroelectrics in sensors and temperature regulators/stabilizers, non-linear capacitors (variconds), electromagnetic radiation receivers and other devices operating in the frequency range from radio waves to visible light. The dependence of ferroelectrics' refractive index on an electric field makes it possible to use them successfully as electro-optical materials.