Ellipsometric studies of NdMnO3 single crystals

Henryk Szymczak Gintautas J. Babonas 1Alfonsas Reza 1Marek Baran 3Jan Fink-Finowicki Sergei V. Shiryaev 2Ritta Szymczak 3

1. Semiconductor Physics Institute, A.Gostauto 11, Vilnius LT-2600, Lithuania
2. The Institute of Solid State & Semiconductor Physics, Belarus NAS (ISSSP), P. Brovka, Minsk 220072, Belarus
3. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland

Abstract


The fine structure of optical spectra of manganites was the object of wide discussions. However, so far the microscopic origin of the optical transitions responsible for the optical features in NIR-VIS-UV region is still not completely understood.
In the present work the ellipsometric studies of NdMnO3 single crystals were carried out. For the first time, all the components of the dielectric function for manganites of orthorhombic symmetry were determined. The analysis of the fine structure of the spectra and optical anisotropy was the basis for the discussion of the microscopic origin of the optical transitions responsible for the optical features. The data for NdMnO3 were compared with those obtained for other perovskites, LaMnO3, LaBaMnCoO3 and LaCaCoO3.
NdMnO3 single crystals of orthorhombic symmetry were grown by electrodeposition technique. Ellipsometric measurements were performed by photometric ellipsometer with rotating analyzer in the spectral range 0.5-5.0 eV. The ellipsometric data obtained on the {001}-type planes were analyzed in the model of biaxial crystal and the dielectric function components were determined. The fine structure of the dielectric function spectra was decomposed into the contributions of several Lorentzian-type lines. From the experimental data the spectra of optical conductivity and loss function were also calculated and analyzed.
Two types of electronic excitations were used for interpretation of the fine structure in the optical spectra. In the region 1-3 eV the optical features are assigned to dipole-forbidden spin-allowed intraconfigurational transitions between crystal-field split 3d levels in Mn-ions. In the region 2-3 eV the structure due to f-f transitions in Nd3+ ions was resolved. In the region of higher photon energies the spectra are due to charge-transfer transition 2p(O)-3d(Mn). The difference between the charge-transfer transitions in NdMnO3 and LaCoO3 is also noticed and discussed.

 

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Presentation: poster at E-MRS Fall Meeting 2003, Symposium D, by Henryk Szymczak
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-11 12:53
Revised:   2009-06-08 12:55