Phase Diagrams of Cubic Systems under Uniaxial Quadratic Symmetry-Breaking Fields

摘要

The effect of uniaxial quadratic symmetry-breaking fields on two- and three-component systems which possess cubic symmetry is studied. A Landau free-energy which includes sixth order terms in the order parameter is constructed and analyzed in the context of mean-field theory. A remarkably rich spectrum of complex phase diagrams featuring several ordered phases is predicted. The phase diagrams exhibit a variety of multicritical points including triple, bicritical, tetracritical, tricritical, and critical-end points. We also predict the existence of two consecutive tricritical points along phase boundaries separating ordered phases. Some of these phase diagrams may be realized in certain compounds corresponding to two- and three-component cubic systems such as Tb2(MoO4)3 and BaTiO3. Keywords: Ferroelectric materials; Barium titanates; Terbium molybdates. (Reprints)