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DF: Fachverband Dielektrische Festkörper

DF 3: Dielectric and ferroelectric thin films 2

DF 3.2: Talk

Monday, March 14, 2011, 15:30–15:50, MÜL Elch

Orbital ordering in head-to-head domain walls — •Kourosh Rahmanizadeh, Gustav Bihlmayer, and Stefan Blügel — Peter Grünberg Institut & Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

Recently, oxide polar interfaces have attracted considerable attention due to the emerging novel behaviors. E.g. the LaAlO₃ / SrTiO₃ interface can induce new properties since the electric potential diverges due to the polar discontinuity at the interface. Electronic localization or defects can help to avoid the divergence of the electric potential and keep an insulating interface.

Also at a ferroelectric head-to-head domain wall there is an uncompensated charge, which could form a two-dimensional electron gas in the insulator. However, the uncompensated charges can be accommodated by partial occupation of the Ti 3d band. We carried out density functional theory calculations based on the full-potential linearized augmented planewave (FLAPW) method as implemented in the FLEUR code (www.flapw.de) to study the PbTiO₃ and BaTiO₃ head-to-head domain wall. The structures have been optimized with GGA and GGA+U. The optimized structure and electronic structure depend on the choice of the Coulomb U. For vanishing U a broad, conducting domain wall is obtained, while increasing U leads to an insulating and sharp domain wall. Also in GGA+U calculations an orbital ordering and a GdFeO₃-like rotation of the TiO₆ octahedra have been found at domain wall.
This work was partly supported by IFOX project of EU-FP7