THE ROLE OF OPTIMIZATION IN THE LANDAU THEORY OF FERROELECTRIC THIN FILMS

Landau-Devonshire theory is a phenomenological theory of ferroelectrics. In this paper a detailed discussion of the application of this theory to ferroelectric films is given; also the interaction of the film with incident electromagnetic radiation is discussed via the Landau-Khalatnikov equations of motion. In particular the role of optimization in the theory is emphasized. It is shown that two important areas to which optimization is relevant are the minimization of the free-energy density, an essential part of the Landau-Devonshire theory, and to the way in which the equations of motion are solved. For the latter it turns out that it is better to work in real variables rather than the complex variables that are convenient to introduce into the formalism prior to the numerical work when dealing with harmonic waves.