First Type of Ferroelectricity Generated by Undulated-Prototypic to Ferroic Transition. II.f=2

Abstract

This paper is concerned with the subject of transitions from artificially incommensurately undulated prototypic phases to ferroic phases. It is possible that such a transition generates ferroelectricity. Ferroelectricity of this category is referred to as U-ferroelectricity, when it needs to be distinguished from conventional ferroelectricity. The most important feature of U-ferroelectricity is that it vanishes when the prototypic phase becomes homogeneous. Several different types of U-ferroelectricity are possible. Only the first and simplest one of those types is dealt with in the present paper. By case study the details are clarified. For example, what term within the free energy function is responsible for the generation of ferroelectricity and in what forms spontaneous polarization and dielectric susceptibility depend on the prototype undulation are clarified.