Order Parameter Distribution and Phase Transition Temperature for a Thin Film With Asymmetric Boundaries

Abstract

The phenomenological theory was developed for the ferroic phase transition in a thin film with asymmetric boundary conditions which simulate the real situation of a film on the substrate or a layer between two different materials. The solutions of the boundary value problem for the order parameter were obtained numerically for some particular sets of phenomenological parameters in the Landau expansion and extrapolation lengths. The main attention was focused on the case of opposite signs of the extrapolation lengths at film surfaces. It was shown that the mean order parameter is close to that in bulk and phase transition temperature remains weakly dependent on film thickness when the extrapolation lengths have similar absolute values and opposite signs.

Keywords:

• Phase transition
• size effect
• thin film
• Landau theory
• asymmetric boundary conditions
• weakened size effect

PACS codes:

• 77.80.B-
• 77.55.-g