Thermodynamic potential and phase diagram for multiferroic bismuth ferrite (BiFeO 3 )

Abstract

We construct a Landau–Ginzburg thermodynamic potential, and the corresponding phase diagram for pristine and slightly doped bismuth ferrite, a ferroelectric antiferromagnet at room temperature. The potential is developed based on new X-ray and neutron diffraction experiments complementing available data. We demonstrate that a strong biquadratic antiferrodistortive-type coupling is the key to a quantitative description of Bi1−x La x FeO3 multiferroic phase diagram including the temperature stability of the antiferromagnetic, ferroelectric, and antiferrodistortive phases, as well as for the prediction of novel intermediate structural phases. Furthermore, we show that “rotomagnetic” antiferrodistortive–antiferromagnetic coupling is very important to describe the ferroelectric polarization and antiferrodistortive tilt behavior in the R3c phase of BiFeO3. The Landau–Ginzburg thermodynamic potential is able to describe the sequence of serial and trigger-type phase transitions, the temperature-dependent behavior of the order parameters, and the corresponding susceptibilities to external stimuli. It can also be employed to predict the corresponding ferroelectric and antiferrodistortive properties of Bi1−x La x FeO3 thin films and nanoparticles by incorporating the gradient and surface energy terms that are strongly dependent on the shape, size, and preparation method.

Peculiarities of the Crystal Structure Evolution of BiFeO3–BaTiO3 Ceramics across Structural Phase Transitions

“…It is known that chemical substitution of bismuth and iron ions allow to modify crystal structure of the compounds and thus change their physical properties, viz. magnetization, resistivity, electromechanical, and magnetoelectric parameters [17][18][19][20][21][22][23][24][25][26].…”

Laminated Modulation of Tricritical Ferroelectrics Exhibiting Highly Enhanced Dielectric Permittivity and Temperature Stability

“…The term f bulk in Equation describes the bulk free energy density, which can be expressed by Landau free energy term in Equation from the previous study . It should be noticed that the multiply terms in Equation decide the stability of ferroelectric phases (T, O, or R) and barriers between different ferroelectric phases, the coefficients of these multiply terms will be zero when the system is at the TP . The selection of the associated coefficients regarding the phase diagram and tricritical phenomenon can be found elsewhere …”

Hierarchical Domain Structure and Extremely Large Wall Current in Epitaxial BiFeO3 Thin Films

“…The bulk free‐energy density f Landau can be expressed using a sixth‐order polynomial expansion, and the elastic energy f ela can be obtained by solving the mechanical equilibrium equation of σ ij . j = 0 under the boundary conditions that the thin film is stress free at the top surface but is fully clamped at the bottom interface .…”