Dresden 2009 – wissenschaftliches Programm

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DF: Fachverband Dielektrische Festkörper

DF 12: Poster II

DF 12.7: Poster

Mittwoch, 25. März 2009, 09:30–12:30, P5

Ab initio characterization of lattice instability in Eu_1−xBa_xTiO₃ multiferroics — •Konstantin Rushchanskii¹, Marjana Ležaić¹, and Nicola Spaldin² — ¹Institut für Festkörperforschung and Institute for Advance Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany — ²Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106-5050

It is well known that chemistry of the A-cation in ferroelectric oxides with a perovskite ABO₃ structure influences the lattice strain and is therefore crucial for the structural instability. Incipient ferroelectrics can be turned to the real ones under negative pressure which in bulk systems can be achieved in solid solutions between chemically related compounds. According to recent observations, similar behavior is observed in a solid solution of EuTiO3 and BaTiO3 perovskite oxides. While pure EuTiO₃ is a quantum paraelectric which also exhibits antiferromagnetic properties, mixed Eu_1−xBa_xTiO₃ compound turns out to be ferroelectric at x>0.2.

We have studied the role of Eu cations on the lattice instability in negatively strained EuTiO₃ and ordered Eu_1−xBa_xTiO₃ compounds for x>0.2. We have found a significant Eu off-centering both in the mixed compounds and in pure EuTiO₃. The influence of hydrostatic pressure on polarization in Eu_1−xBa_xTiO₃ have also been studied, which allowed us to derive a phonon picture of the observed Eu cation off-centering together with its detailed electronic structure view.