Structural Determination of Epitaxial Formations in Layered Cuprates

The fragment approximation is used for the description of the layered cuprate structures. The characteristic structural features are distinguished which genetically relate all the layered cuprates. The classification scheme for the whole family of layered cuprates is analyzed in the fragment approximation and a possible extension of the scheme is discussed

Epitaxial Intergrowth of Isostructural Phases in Bi-2212 Single Crystals

The isostructural phases in Bi-2212-type HTSC were studied by structural and optical methods. The epitaxial intergrowth was shown to be a feature typical of single crystals composed of several isostructural phases. The physical properties of the multi-phase samples were interpreted on the basis of reference mono-phase samples. A presence of the intergrowth interface was assumed to be responsible for particular features in multi-phase samples

OPTICAL SPECTRA OF THE A2B2C52TYPE SEMICONDUCTORS

Les spectres d'absorption et les spectres dérivés obtenus par la méthode de modulation de longueur d'onde ont été étudiés au voisinage du bord d'absorption fondamentale de composés ternaires A2B2C52 à gap pseudo-direct. Les spectres de réflexion de quelques composés A2B2C52 à gap direct ont été mesurés dans la région de 1 à 12 eV et exploités par analyse de Kramers-Kronig.The wavelength modulated and conventional absorption spectra of pseudodirect bandgap A2B2C52 compounds have been investigated in the region of the absorption edge. The reflectance spectra of some direct bandgap A2B2C52 semiconductors have been measured in the range 1 to 12 eV and the Kramers-Kronig analysis has been performed

Spectral ellipsometry of La1-xMnO3 films with different degree of epitaxy

The dependence of the optical spectra of La1-xMnO3 films on the degree of epitaxy was investigated. Films of La1-xMnO3-δ (x ≈ 0.1) were grown by metal organic chernical vapor deposition on SrTiO3 and Al2O3 (r-plane cut) substrates. The films are supposed to possess a different degree of epitaxy because of various matching conditions between substrate and film lattices. The optical spectra were obtained in the range 0.5-5.0 eV by spectroscopic ellipsometry technique making use of photometric ellipsometer. Fine structure in the spectra of pseudodielectric function is discussed taking into account the excitations of Drude-type free electrons along with the charge-transfer 2 p(O) → 3d(Mn) and dipole-forbidden d-d(Mn3+) transitions. In this model the difference in the spectra of two type samples with different degree of epitaxy was considered

Magnetic Properties of Spin-Ladders (A2\text{}_{2}Cu2\text{}_{2}O3\text{}_{3})m\text{}_{m} (CuO2\text{}_{2})n\text{}_{n}

Magnetization M(T) and M(H) data of single crystals of the S=1/2 quasi-one-dimensional system (A$\text{}_{2}$Cu$\text{}_{2}$O$\text{}_{3}$)$\text{}_{m}$(CuO$\text{}_{2}$)$\text{}_{n}$ with various A-site constituents are compared. The studied orthorhombic, incommensurate crystals are characterized by m/n=5/7,7/10, and 9/13. The role of rare-earth ions located in A-sites is discussed

Ellipsometric Studies of NdMnO 3

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$\text{}_{3}$

Ellipsometric Studies of NdMnO3\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$\text{}_{3}$

Optical Response of La1−x\text{}_{1-x}MnO3\text{}_{3}/Al2\text{}_{2}O3\text{}_{3} Films

La$\text{}_{1-x}$MnO$\text{}_{3}$ films grown by metal organic chemical vapor deposition technique on r-plane cut Al$\text{}_{2}$O$\text{}_{3}$ substrates were investigated. The change of the optical response over the La$\text{}_{1-x}$MnO$\text{}_{3}$/Al$\text{}_{2}$O$\text{}_{3}$ sample surface was investigated along with the temperature dependence of magnetization. The mostly pronounced difference in the spectra of dielectric function occurred in the region of the d-d transitions of Mn-ions. The changes in the optical spectra and magnetic properties were correlated to the structural features of thin film