Curie phase transition and critical size for ferroelectricity in strained ultrathin PbTiO3 and BaTiO3: A phenomenological study

Modified Landau-Ginzburg-Devonshire phenomenological theory was used to investigate the influence of substrate constraint, surface effect, and depolarizing field on Curie phase transition and critical size for ferroelectric instability in ultrathin PbTiO3 and BaTiO3. The calculated thickness dependence of transition temperature and polarization for epitaxial films on various substrates was compared with relevant experimental results, so as to evaluate the applicability of macroscopic phenomenology in ultrathin films. Our calculations of charge-compensated PbTiO3 and uncompensated BaTiO3 are essentially in reasonable agreement with the previous measurements.