BiFeO3 domain wall energies and structures: a combined experimental and density functional theory+U study

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Bismuth ferrite (BiFeO3) is a multiferroic material with potential applications in data storage and sensors.
• Understanding domain wall structures and energies is crucial for optimizing its properties.
• Previous studies have provided limited insights into the atomic-level details of different domain wall types.

Purpose of the Study:

• To determine the atomic structures and energies of 109°, 180°, and 71° domain walls in BiFeO3.
• To correlate domain wall energies with specific atomic arrangements and rotations of oxygen octahedra.
• To provide a comprehensive understanding of domain wall behavior in BiFeO3.

Main Methods:

• Density functional theory+U (DFT+U) calculations were employed to model atomic structures and energies.
• Aberration-corrected transmission electron microscopy (TEM) images were used for experimental validation.
• Analysis focused on Bi and Fe sublattice shifts and oxygen octahedra rotations across domain walls.

Main Results:

• Atomic structures and energies for 109°, 180°, and 71° domain walls were successfully determined.
• A significant Bi sublattice shift and a uniform Fe sublattice were observed across the domain walls.
• The domain wall energies followed the sequence: γ109 < γ180 < γ71.

Conclusions:

• The high energy of the 71° domain wall is attributed to opposite tilting rotations of oxygen octahedra.
• The low energy of the 109° domain wall is attributed to opposite twisting rotations of oxygen octahedra.
• These findings offer critical insights into the structure-property relationships of BiFeO3 domain walls.