In our recent work, we addressed a long-standing puzzle in ferroelectric research: the origin of unusual zigzag and pyramidal domain structures in the multiferroic material BiFeO3. These complex patterns had been observed experimentally for years, but their physical cause remained unclear. Using phase-field simulations within the Landau–Ginzburg–Devonshire framework, we demonstrated that they can naturally form when defect charges are distributed homogeneously in the crystal. The system compensates these charges by creating pyramid-like domains in which the polarization rotates to lower the overall energy. Our simulated patterns agree closely with transmission electron microscopy observations of BiFeO3 crystals from our colleagues at the University of Warwick, giving strong support to our model. Beyond solving a fundamental question, this insight has practical value. The pyramidal domains are highly regular and self-assembled with nanometer-scale periodicity, making them attractive for applications requiring precise ordering, such as optics or topological defect-based devices.
a) 3D visualization of the wall surface. b) Ferroelectric polarization visualized in the plane (-110). c) Distance of the domain wall from the center of the charged layer measured along [111]. d) Deviation of the polarization from the pyramid’s axis. Polarization is projected to two selected planes, color indicates polarization component perpendicular to [111] direction. Red: positive, blue: negative, white: no deviation.
Contact person: Pavel Márton