Papers by Author: Pietro Galinetto

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Authors: Maria Cristina Mozzati, Andréy G. Badalyan, Giulia Demaestri, Pietro Galinetto, Francesco Rossella, Veronica Bermúdez, Carlo B. Azzoni, Giorgio Samoggia
Abstract: EPR and optical absorption measurements have been performed on nearly stoichiometric lithium niobate single crystals with iron in traces and in 0.1% molar nominal amount. Thermal treatments in reducing atmosphere allowed to obtain samples with different Fe2+/Fe3+ ratios. The Fe2+/Fe3+ dynamic has been observed by irradiating the samples with UV and visible light in the temperature range 4-300 K: the photochromic effect resulted to be more evident in the strongly reduced crystals. A simple model to explain the photochromic behavior in nearly stoichiometric LiNbO3:Fe is proposed.
Authors: Andréy G. Badalyan, Carlo B. Azzoni, Pietro Galinetto, Maria Cristina Mozzati, Lubomir Jastrabik, Jan Rosa, Miroslav Hrabovsky, P.P. Syrnikov, V.A. Trepakov
Abstract: The UV illumination effects in KTaO3 single crystals with Cu2+ impurity ions have been studied by electron paramagnetic resonance method. Single crystals both “as-grown” and thermally treated in oxygen atmosphere were investigated. It was found that the EPR signal of the Cu2+ centers decreases in the “as-grown” crystals during UV-irradiation at 365 nm, in the wholeinvestigated temperature range (3.7- 300 K). On the contrary, for the oxidized specimens a sizeable increase of the EPR signal of Cu2+ centers (except the signal from exchange coupled pair centers) is observed under UV illumination in some temperature regions.
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