Penn State MRSEC NSF DMR-0820404, 0507146 & 0602986 Physical Review B 80 , 060102(R) (2009)

1. Bloch and Néel Walls in Ferroelectrics P. Wu, Y. Li, D. Lee, S. Sinnott, S. Phillpot, L. Q. Chen, V. Gopalan Penn State MRSEC NSF DMR-0820404, 0507146 & 0602986 Physical Review B 80, 060102(R) (2009) Ferroelectric 180° domain walls are predominantly Ising-like, unlike many magnetic walls which are Bloch and Néel type. Using density functional theory and molecular dynamics simulations, MRSEC researchers show that the 180° domain walls in prototypical ferroelectrics lead titanate PbTiO3 and lithium niobate LiNbO3 have mixed Ising, Bloch and Néel like character. The mixed character can be dramatically enhanced in nanoscale thin-film heterostructures, such as 8 unit cells of BaTiO3 (BT) stacked with 4 unit cells of SrTiO3 (ST). The wall interior forms broad and tunable Bloch and Néel-like polarization vortices. Highly tunable exchange-spring ferroelectrics – similar to well-known exchange spring magnets which are very useful in magnetic information storage – are envisioned.