ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 56, (2) 95 - 101 (2012)


OPTICAL INVESTIGATIONS OF La0.7Ca0.3-xKxMnO3 (x = 0.00, 0.05 and 0.10) PROBED BY SPECTROSCOPIC ELLIPSOMETRY
 
Sdiri N. 1, Boukhachem A. 2, Dhahri E. 1
 
1 Laboratoire de Physique Appliquée, Faculté des Sciences de Sfax, Tunisia
2 Unité de physique des dispositifs à

Keywords: K doped manganites, Spectroscopic ellipsometry, Complex index, Dispersion, Phase transition
 

Using spectroscopic ellipsometry, we have studied the optical properties of doped manganites at the paramagnetic state in polycrystalline La0.7Ca0.3-xKxMnO3 samples for (x = 0.00, 0.05 and 0.10) in the energy range of 3.2-5.5 eV at room temperature. The surface morphology of the samples was obtained by using atomic force microscopy (AFM). Refractive indices, extinction coefficients, the transmission ellipsometric parameters Ψ and Δ are investigated at different wavelengths. The study of the optical conductivity σ reveals that optical behaviour and the activated transport in the paramagnetic state of these materials are consistent with Jahn-Teller small polaron. In addition, the spectrum of the complex dielectric constant ε reveals peaks for all samples, the results may be explained by the presence of space charges from the strongly dipole-allowed O(2p)−Mn(3d) transition.


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