Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 7: Multiferroics II (with DF, KR, DS)

MA 7.8: Vortrag

Montag, 22. März 2010, 16:00–16:15, H3

Mechanism of ferroelectric instabilities in non-d⁰ perovskites: LaCrO₃ versus CaMnO₃ — Tim Harris, Roman Kovacik, and •Claude Ederer — School of Physics, Trinity College Dublin, Ireland

The incompatibility of partial d occupation on the perovskite B-site with the standard charge transfer mechanism for ferroelectricity has been a central paradigm in multiferroics research [1]. Nevertheless, it was recently shown by density functional theory calculations that CaMnO₃ exhibits a polar instability that even dominates over the octahedral tilting for slightly enlarged unit cell volume [2]. Here, we present similar calculations for LaCrO₃, which has the same d³ B-site electron configuration as CaMnO₃. We show that LaCrO₃ exhibits a similar, albeit somewhat weaker, volume-dependent polar instability as CaMnO₃, but while the Born effective charge (BEC) for the Mn⁴⁺ cation in CaMnO₃ is highly anomalous, the BEC for Cr³⁺ in LaCrO₃ is only slightly enhanced. We decompose the BECs for both systems in contributions of individual Wannier functions to elucidate the different driving force behind the polar instability in these systems.

[1] N. A. Hill, J. Phys. Chem. B 104, 6694 (2000). [2] S. Bhattacharjee et al., Phys. Rev. Lett. 102, 117602 (2009).

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