TEMPERATURE DEPENDENCE OF THE SHAPE OF THE DOMAIN WALL IN FERROMAGNETIC$ AND FERROELECTRIC$

The 180° domain wall in ferromagnetic and ferroelectric substances is considered over a broad temperature range. Analytical solutions, however, are derived only near the Curie temperature; at lower temperatures only a qualitative picture is presented. The shape of the wall and its character as a whole should in general change significantly on going from low to high temperatures (region of Curie point). For example, in uniaxial ferromagnetic crystals, beginning at a certain temperature and up to the Curie point, the magnetization in the domain wall as well as in the domain volume is directed only along the axis of easiest magnetization. In Rochelle salt the solution should be exactly of this type if use is made of all known constants in the expression for the free energy.