Fig. 4: Phase-field simulations of polar topological structures of BFO islands with different diameters.
From: Observation of multi-order polar radial vortices and their topological transition
a–c Schematics of the nanostructures including the disc-shaped BFO islands and the surrounding BFO matrix, with the diameters of the nanostructures being d, 2 d, and 3 d, respectively. d–f Planar view of out-of-plane polarization and Pontryagin density distributions in BFO nanostructures with diameters of d, 2 d, and 3 d. g–i The local out-of-plane polarization distributions along a horizontal line through the center of BFO nanostructures with diameters of d, 2 d, and 3 d.
