Smearing of phase transition due to a surface effect or a bulk inhomogeneity in ferroelectric nanostructures

TL;DR

This paper investigates how surface effects and inhomogeneities in ferroelectric nanostructures modify phase transition behavior, often smearing or suppressing sharp transitions and promoting domain formation.

Contribution

It introduces modified boundary conditions accounting for surface fields, revealing their impact on phase transition suppression and domain structure emergence in ferroelectric nanostructures.

Findings

Surface fields suppress second-order phase transitions.

Inhomogeneities can prevent monodomain transition.

Domain structures may form instead of sharp phase changes.

Abstract

The boundary conditions, customarily used in the Landau-type approach to ferroelectric thin films and nanostructures, have to be modified to take into account that a surface of a ferroelectric (FE) is a defect of the ``field'' type. The surface (interface) field is coupled to a normal component of polarization and, as a result, the second order phase transitions are generally suppressed and anomalies in response are washed out. In FE films with a compositional (grading) or some other type of inhomogeneity, the transition into a monodomain state is suppressed, but a transition with formation of a domain structure may occur.