Nanoscale phase separation in La0.7Ca0.3MnO3La_{0.7}Ca_{0.3}MnO_3 films: evidence for the texture driven optical anisotropy

The IR optical absorption (0.1-1.5 eV) in the $La_{0.7}Ca_{0.3}MnO_3$ films on LAO substrate exhibits the drastic temperature evolution of the spectral weight evidencing the insulator to metal transition. Single crystal films were found to reveal strong linear dichroism with anomalous spectral oscillations and fairly weak temperature dependence. Starting from the concept of phase separation, we develop the effective medium model to account for these effects. The optical anisotropy of the films is attributed to the texturization of the ellipsoidal inclusions of the quasimetal phase caused by a mismatch of the film and substrate and the twin texture of the latter.Comment: 6 pages, 5 Encapsulated PostScript figures, uses RevTeX

Nanoscale Phase Separation in La0.7Ca0.3MnO3 Films: Evidence for Texture-driven Optical Anisotropy

The infrared optical absorption (0.1 eV < ℏω < 1.5 eV) in La0.7Ca0.3MnO3 films on LaAlO3 substrates exhibits a drastic temperature evolution of the spectral weight, evidencing an insulator-to-metal transition. Single-crystal films were found to reveal strong linear dichroism with anomalous spectral oscillations and fairly weak temperature dependence. Starting from the concept of phase separation, we develop an effective medium model to account for these effects. The optical anisotropy of the films is attributed to the texturization of the ellipsoidal inclusions of the quasimetal phase caused by a mismatch of the film and substrate and the twin texture of the latter.The work was supported by INTAS 01-0654, Federal programme (contract No 40.012.1.1. 1153-14/02), grants RFBR No 01-02-96404, No 02-02-16429, RFMC No E00-3.4-280, E02-3.4-392, CRDF No REC-005 and UR 01.01.042

Formation of CdxPb1−xS/Cd1-δS Thin-film Two-phase Compositions by Chemical Bath Deposition: Composition, Structure, and Optical Properties

The possibility of forming thin-film two-phase compositions CdxPb1-xS/Cd1−δS using chemical bath deposition from aqueous media with adding various cadmium salts has been demonstrated. The crystal structure, chemical composition, morphology, and the band gap were studied by the X-ray diffraction, scanning electron microscopy, elemental analysis, Auger and Raman spectroscopy, and diffuse reflectance measurements. The formation of a CdxPb1−xS/Cd1−δS substitutional solid solution phase in well-faceted crystallites on the substrate of an X-ray amorphous CdS phase was experimentally shown. The observed difference in the composition of the films deposited with adding different cadmium salts is the result of the effect of the nucleophilicity of the anionic component of these salts on the kinetics of thiourea decomposition. The results demonstrate the possibility of forming thin-film two-phase compositions or heterostructures on the base of cadmium and lead sulfides in one technological stage using chemical bath deposition, which can be important for the creation of solar cells. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.The research was financially supported in part by 211 Program of the Government of the Russian Federation (No. 02.A03.21.0006), was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (Themes No. AAAA-A18-118020190112-8 (“Flux”), No. AAAA-A18-118020290104-2 (“Spin”), and No. AAAA-A19-119031890025-9) and in part supported by RFBR (projects No. 18-29-11051-mk, 20-48-660041-r-a)

Appearance of itinerant electrons detected by IR spectroscopy and its correlation with surface magnetism in Co-doped TiO2 nanopowders

IR absorption and magnetic data for the titanium dioxide nanopowders are studied. Additional absorption in IR range is revealed in nanocrystalline TiO2 and Co-doped TiO2 after reducing annealing and explained by appearance of the oxygen vacancies and delocalised charge carriers. Increasing of the absorption in IR range after annealing of Co-doped TiO2 in vacuum (or decreasing of this contribution after annealing in air) correlates with arising (or vanishing) of ferromagnetic contribution. © 2018 The Authors, published by EDP Sciences.This work was supported by the Russian Scientific Foundation, Grant No. 16-12-10004

Optical indication of metallic clusters in the layered manganites

Optical absorption in the bi-layered manganites \chem{La_{2 - 2{\it x}}Sr_{1 + 2{\it x}}Mn_{2}O_{7}} ($x=0.3$ and 0.4) was studied and metallic clusters were revealed in the temperature range T_\ab{C} in the composition with $x=0.4$. The existence of metal clusters is considered as the principal cause of magnetoresistance, the tails of magnetization and ferromagnetic correlations, which are observed in this manganite up to temperatures several times exceeding the temperature T_\ab{C} of 3D magnetic ordering