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TT: Fachverband Tiefe Temperaturen

TT 11: Ferroelectric Domain Walls I (joint session KFM/TT)

TT 11.2: Vortrag

Montag, 12. März 2018, 10:00–10:15, EMH 225

Charged domain walls and point defect-DW interactions in hexagonal manganites — Didrik Rene Småbråten¹, Quitin Meier², Sandra Helen Skjaervoe¹, Thomas Tybell¹, Dennis Meier¹, and •Sverre Magnus Selbach¹ — ¹NTNU Norwegian University of Science and Technology, Trondheim, Norway — ²Materials Theory, ETH Zurich, Zürich, Switzerland

Charged head-to-head and tail-to-tail ferroelectric domain walls (DW) in hexagonal manganites are stable because of the improper nature of the ferroelectricity in these materials, and it has been experimentally shown that their electronic properties can differ strongly from bulk. First principles studies of charged DWs are scarce and the inherent electrostatic fields make DFT calculations challenging. Here we combine density functional theory (DFT) calculations with a continuum model based on Landau theory to study the properties of charged DWs in YMnO₃, InMnO₃ and isostructural YGaO₃. We find excellent agreement between the micro- and macroscopic models, and show that the Mexican hat energy landscape of hexagonal maganites derived from Landau theory also emerges naturally from DFT calculations of their DWs. Head-to-head and tail-to-tail DW are structurally inequivalent due to the different local chemical bonding. We formulate a general criterion based on polarization and band gap for when charged DWs become conducting. Finally, we study interactions between DWs and oxygen interstitials and vacancies by DFT.