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DF: Fachverband Dielektrische Festkörper

DF 11: Poster Session

DF 11.25: Poster

Donnerstag, 29. März 2007, 14:30–18:00, Poster C

Second harmonic generation studies of Sr_1−xBa_xNb₂O₆ single crystals — •Markus Heckhoff, Theo Kleinefeld, Vladimir Shvartsman, and Wolfgang Kleemann — Angewandte Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany

Sr_1−xBa_xNb₂O₆ (SBN) are polar oxides with the unfilled tungsten bronze structure and a single component order parameter. Upon increasing the Sr²⁺ concentration x a gradual transformation from ferroelectric to relaxor behavior is observed. The mechanism of this transformation is still under discussion and targeted investigations are urgently demanded. We present results of second harmonic generation (SHG) studies of SBN single crystals with different Sr/Ba ratios (x = 0.4, 0.5, 0.61, 0.75). Since the intensity of the SHG signal in polar materials is proportional to the polarization squared, this method is useful for investigating the phase transition. From the temperature dependence of the SHG signal, I_2ω(T), we obtained information on the evolution of the order parameter in the vicinity of the Curie temperature. The SHG data for compositions from ferroelectric (x=0.4) to extreme relaxor-like (x=0.75) SBN are compared. In order to obtain information on the domain structure, I_2ω(T) was analyzed as a function of the light incidence angle.