Berlin 2015 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 12: Poster Session on Ferroic Domain Walls - Multiferroics (DF with KR/MA/TT)

MA 12.7: Poster

Montag, 16. März 2015, 19:00–21:00, Poster C

Domain walls in lithium niobate investigated by Raman spectroscopy and density functional theory — •Sergej Neufeld¹, Michael Rüsing², Gerhard Berth², Artur Zrenner², Wolf Gero Schmidt¹, and Simone Sanna¹ — ¹Lehrstuhl für Theoretische Physik, Universität Paderborn — ²Department Physik, Universität Paderborn

The intensity of the Raman signal associated to different phonon modes of LiNbO₃ is strongly modified by the presence of ferroelectric domain boundaries [1]. The intensity modulation can be exploited to map domain structures, thus using Raman spectroscopy as a non-destructive imaging tool for the investigation of polarization-domains and domain walls [2]. Unfortunately, the origin of the modifications in the Raman signal is currently unknown. In an attempt to understand the mechanisms leading to the modification of the measured intensity, we have modeled Raman scattering efficiencies from first-principles. Thereby the Raman susceptibility tensor is calculated within the density functional theory following the approach proposed by Ghosez and co-workers [3]. The approach is validated with the TO bulk phonon modes of A₁ and E symmetry and then applied to domain boundaries. The bulk Raman intensities calculated for all possible combinations of the polarization of incoming and scattered photons are in good agreement with the measured spectra. Results for simplified domain wall models are presented and discussed. [1]P. S. Zelenovskiy et. al., Appl. Phys. A 99, 741 (2010). [2]G. Berth et al., Ferroelectrics 420, 44 (2011). [3]M. Veithen et al., Phys. Rev. B 71, 125107 (2005).