Strain induced vortex-to-uniform polarization transitions in soft-ferroelectric nanoparticles

Abstract

Domain structures of ferroelectric polarization in patterned nanostructures depend sensitively on an interplay between their geometry and crystallographic anisotropy. In the recently predicted layered perovskite PbSr2Ti2O7 [S. M. Nakhmanson and I. Naumov, Phys. Rev. Lett. 104, 097601 (2010)], the in-plane anisotropy can be controlled by strain to be along in-plane [110]-directions or to vanish, in which case the polarization is free to rotate in the perovskite-layer. Using a microscopic Landau-Ginzburg-Devonshire free energy functional theory, we demonstrate that the domain structure in patterned disks of PbSr2Ti2O7 can be varied between uniform polarization and a vortex structure, analogous to vortices in soft magnetic disks. This opens up the possibility of designing nanostructured layered materials whose dielectric response can be manipulated with small elastic distortions.