SYSTEM OF 2 (NOT ONE) DECLENSION PARAMETERS FOR PROTOTYPE UNDULATION - RELATED U-FERROELECTRICITY

This paper is concerned with a transition from an artificially incomme nsurately undulated prototypic phase to a ferroic phase, and also with U-ferroelectricity (which means ferroelectricity that should vanish i f the prototypic phase is brought from undulated to homogeneous). Prot otype undulation can be represented by the undulation of a set of decl ension parameters (denoted by delta, epsilon,). All previous papers th at dealt with prototype undulation assumed only one declension paramet er. In contrast the present paper assumes two. One case is studied, wh ose definition includes assuming delta = U-delta COS((h) over cap x <(theta)over cap>(delta)) and epsilon = U-epsilon cos((h) over cap x <(theta)over cap>(epsilon)) with all high harmonics ignored. The expr essions of spontaneous polarization and dielectric susceptibility are deduced, the former of which indicates that, if and only if U-delta no t equal 0, U-epsilon not equal 0 and sin (<(theta)over cap>(delta) - < (theta)over cap>(epsilon)) not equal 0, the ferroic phase is ferroelec tric.