Ellipsometric Studies of NdMnO$\text{}_{3}$ Single Crystals

Ellipsometric studies of NdMnO$\text{}_{3}$ single crystals of orthorhombic symmetry were carried out in the spectral range 0.5-5.0 eV. Experimental data, which were obtained on the (001)$\text{}_{pc}$-type planes of pseudo-cubic system, were analyzed in the model of biaxial crystal. For the first time, three componentsε$\text{}_{x}$,ε$\text{}_{y}$,ε$\text{}_{z}$ of the effective dielectric function for manganites of orthorhombic symmetry were determined. From ellipsometric data, the spectra of optical conductivity and loss function were also calculated and considered. The fine structure of the spectra and optical anisotropy was the basis for discussion of the microscopic origin of the optical transitions responsible for the optical features. The electronic excitations due to dipole-forbidden spin-allowed transitions of the d-d-type in Mn-ions, f-f-type in Nd-ions and charge-transfer 2p(O)-3d(Mn) transitions were taken into account. The data for NdMnO$\text{}_{3}$ were compared with those obtained for other related undoped and doped single crystals of perovskite-type structure, LaMnO$\text{}_{3}$, (LaBa)(MnCo)O$\text{}_{3}$ and (LaCa)CoO$\text{}_{3}$.