superlattices as geometric ferroelectrics

Structural distortions in orthorhombic perovskite structures have been suggested as a source of ferroelectricity in layer-by-layer grown heterostructures of transition metal oxides. Here we explore the idea to achieve a multiferroic state by epitaxial growth in superlattices of LaVO₃ and PrVO₃. Heterostructures were synthesised by pulsed laser deposition and investigated by X-ray diffraction in order to determine the pattern of the oxygen octahedra. Cation polar distortions were measured by scanning tunnelling electron microscopy in order to confirm the prediction that superlattices with odd repetitions of LaVO₃ and PrVO₃ layers present a macroscopic ferroelectric state.