Landau Theory Analysis of Dielectric Properties of BiFeO3 Ferroelectric Thin Films

Abstract

Abstract: The dielectric properties and phase transition behavior of BiFeO₃ (BFO) ferroelectric thin films are explored using Landau-Ginzburg-Devonshire theory, accounting for polarization variation near the surfaces. The Euler-Lagrange (E-L) equation is numerically solved to model switching properties under an applied step electric field. Dielectric hysteresis loops are generated for various thicknesses and temperatures, revealing a critical thickness of 0.452 nm, revealing a critical thickness of 0.452 nm, which highlights BFO’s potential for nanoscale applications. The electric susceptibility is computed for several film thicknesses, showing a high value (~10⁴) near the transition temperature, even for a film thickness of 1 nm. At room temperature, the susceptibility increases as the film thickness decreases, reaching a value of 51.7 at 30 °C for the 1 nm film. These findings are consistent with experimental observations that report an average dielectric constant of approximately ~50 in a single BFO crystal. Additionally, at room temperature, the calculated average polarization for BFO films with thicknesses between 1 nm and 6 nm falls in the range 0.50–0.55 C/m², indicating a relatively high value compared with other ferroelectric materials.