Eur. Phys. J. B 52, 143-150 (2006)
https://doi.org/10.1140/epjb/e2006-00271-1

Surface state on first-order ferroelectrics

¹ School of Physics, Universiti Sains Malaysia, 11800 USM Penang, Malaysia
² Faculty of Business, Aichi Shukutoku University, Nagakute-cho, Aichi, 480-1197, Japan
³ School of Microelectronic Engineering, Kolej Universiti Kejuruteraan Utara Malaysia (KUKUM), Jejawi 02600, Arau Perlis, Malaysia
⁴ Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hongkong, P.R. China

Corresponding author: ^a junaidah@usm.my

Received: 10 March 2006
Revised: 7 June 2006
Published online: 6 July 2006

Abstract

In the presence of a surface the Landau-Devonshire equations of ferroelectricity must be extended to include a boundary condition. For a ferroelectric with a second-order transition in the case when the polarization p(z) increases at the surface, it is well known that a surface state occurs in a range of temperature above the bulk critical temperature t_CB . Here we explore the corresponding effect for a first-order ferroelectric. We show that a surface state can occur, but only if the surface effect is sufficiently strong. Analytic expressions are derived and illustrated for p(z), the surface value p_S =p(0) and the free energy. The transition from the paraelectric state (p=0) to the surface state is first order, and for completeness we establish the dependence of the three critical temperatures (supercooling, thermodynamic and superheating) on a boundary-condition parameter y. In a final section, we derive and illustrate expressions for p(z)in the temperature range t<t_CB .