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Double manganite PrBaMn2O6 with ordered alternate stacking of PrMnO3/BaMnO3 layers attracts a special interest due to presence of two magnetic phase transitions close to room temperature; that makes it perspective magnetocaloric and magnetoresistive material. Besides the magnetic phase transition, the structural transition accompanied with the elongation of the a-axis and the contraction of the c-axis was experimentally detected. The origin of structural phase transition is studied by X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), IR absorption spectroscopy, magnetometry and dynamical mean-field theory (DMFT) for electronic structure calculations. It is found that the structural phase transition is caused by splitting of eg-doublet states due to the tendency towards orbital ordering at the metal-insulator phase transition.

The calcium-doped PbS films are produced by using the chemical bath deposition method (CBD) on glass and sitall substrates. The influence of the calcium doping on the structural, morphological and optical properties of these films is studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical spectroscopy, and energy dispersive X-ray spectroscopy (EDX). The lead sulfide films have cubic structure (B1). The inclusion of calcium in the crystal structure of PbS up to 0.11 at. % is confirmed by the elemental, radiographic and energy-dispersive analyzes. The band gap Eg in the undoped PbS film is estimated as 0.40 ± 0.01 eV at 295 K and 0.38 ± 0.01 eV at 90 K and decreases with calcium doping by ∼0.02 eV. It is shown that doping of lead sulfide films with calcium by adding CaCl2 up to 5.0 mmol/l results in the increase in the photoresponse to IR radiation in 1.7 times.

For double manganites PrBaMn2O6 with different degree of A-site ordering, magnetic and optical properties in near-IR range were studied. Full ordered manganite is characterized by antiferromagnetic state at low temperatures; magnetic phase transition from antiferromagnetic to ferromagnetic state occurs near TN = 262 K and to paramagnetic state near TC = 305 K. Partially disordered manganite consists of few fractions with different state of A-site ordering and shows the transition from ferromagnetic state to paramagnetic one at 190 K. For disordered manganite weak ferromagnetic contribution is observed below 130 K. The optical density spectra and the temperature dependences of light transmission indicate a change in behavior of the charge carrier system (metal–insulator transition) near the magnetic phase transitions. The magnetotransmission effect was measured for the first time in double manganites PrBaMn2O6. Spectral dependence of magnetotransmission lets associate this effect with an increase in the fraction of delocalized charge carriers when a magnetic field is applied.

Films of cubic substitutional CdxPb1−xS solid solutions have been synthesized by the chemical bath deposition with varying cadmium acetate salt Cd(CH3COO)2 in the reaction mixture within 0.01–0.08 mol/l on quartz substrates. The crystal structure, chemical composition and morphology were studied by the X-ray diffraction, scanning electron microscopy, elemental analysis, Auger spectroscopy, and Raman spectroscopy, as well as the evolution of the optical and photoelectric properties was determined. The thickness of the deposited films changes from ~ 0.4 to ~ 1.0 μm, and the content of cadmium x in the CdxPb1−xS solid solution varies from 0.036 to 0.090. All the CdxPb1−xS films have B1 crystal structure (NaCl type), but differ in the morphology (the size, form and predominant orientation of the particles forming the films). Forming the substitution solid solution is confirmed by the shift of the Raman lines at 72 and 134 cm−1 toward higher frequencies. The optical band gap determined from the absorption spectra varies from 0.46 to 0.70 eV. The dependences of the photoresponse value (volt-watt sensitivity) and the dark resistance on cadmium acetate concentration in the solution are represented.

Thin polycrystalline films of cubic lead sulfide doped with iron (II) PbS:Fe have been synthesized by chemical bath deposition from aqueous solutions of lead acetate, sulfidizing agent, and complexing and alkaline agents in the presence of FeCl2 salt in the concentration range from 10−5 to 7 × 10−3 M. At the iron (II) chloride concentration lower than [FeCl2] = 5 × 10−3 M, the crystal lattice parameter of PbS increases indicating the interstitial position of Fe2+ ions. At [FeCl2] = 5 × 10−3 M, the substitution of iron ions for lead ones is found. The absorption spectra show that on increasing FeCl2 concentration in the reaction bath up to 10−3 M, the band gap of the synthesized PbS:Fe films hardly changes (Eg∼0.4 eV); only the growth of the impurity bands near the absorption edge is observed. At [FeCl2] = 5 × 10−3 M, the blue shift of the absorption edge occurs, the band gap increases to 0.58 eV, and the impurity absorption band shifts toward the higher energies. Cooling the films in the magnetic field influences the intensity of the impurity absorption bands associated with iron when Fe2+ ions are located in interstitial position. The observed changes in the optical spectra are explained by the difference in the band structure and the position of the impurity levels when Fe2+ ions are at the interstices or in the Pb ions position.

The magnetic, transport and elastic properties of CaMn 0.96 Mo 0.04 O 3 polycrystal are reported. The magnetic data of the paramagnetic region point to the magnetic polarons. The transition from the paramagnetic state into the antiferromagnetic state of G-type occurs near 93 K, the crystal orthorhombic structure being unchanged. The transition from the paramagnetic orthorhombic phase into the C-type antiferromagnetic monoclinic phase is revealed at about 130–140 K, the transition taking place in small regions of the sample.

The magnetic properties of nanopowders of Nd0.5Sr0.5MnO3 manganite, obtained by ball milling method, and IR magnetotransmission (the relative change in transmission of infrared radiation in a magnetic field) of composites based on the nanopowders are studied and compared with properties of Nd0.5Sr0.5MnO3 single crystal and coarse grain powder. The strong decrease of the magnetization at transformation of the single crystal to coarse grain powder is associated with the martensitic nature of the charge-ordered state (CO), TCO∼150 K. With a further decrease of particles size the magnetization decreases sharply above 150 K and is less significant in the region below 150 K, where a plateau in temperature dependence of magnetization and magnetotransmission takes place. The plateau is explained by modification of the manganite properties at milling and associated with competition of the ferromagnetic and antiferromagnetic contributions in cores and surface of the nanoparticles and change in the degree of localization of charge carriers in the magnetic field. The high value of the magnetotransmission (up to 9%) in a wide temperature range for nanocomposites are promising for creation of magnetically controlled infrared optoelectronic devices.

Magnetic, transport and optical properties of the Ca0.85Eu0.15MnO3 single crystal are studied and discussed in comparison with the properties of polycrystalline sample. The magnetic data show existence the two magnetic phase transitions under cooling: the transition near 150 K occurs from the paramagnetic orthorhombic to C-type antiferromagnetic monoclinic phase with the charge/orbital ordering in some part of the crystal; and at 90 K the transition from the paramagnetic to G-type antiferromagnetic phase takes place in another part of the crystal with the orthorhombic structure. The magnetoresistance of the Ca0.85Eu0.15MnO3 single crystal has features at temperatures of these phase transitions. Differences in the properties of single crystal and polycrystalline sample with the same content of Eu are associated with the ordering of oxygen vacancies that appear under the crystal growth. The reflection spectra in infrared range confirm the existence of the electron conductivity in a narrow band at room temperature.

We demonstrate that the colossal magnetoresistance (CMR) manganites doped with the monovalent cations of the large ionic radius A (A = Na+, K+, Ag+) reveal enhanced sensitivity of the electrical resistance to the magnetic field near the room temperature. The main obstacle to their practical application is severe difficulty of the synthesis, in particular, that of the thin films because of the high volatility or low thermal stability of the oxides of these doping elements. But the preparation of the films in two steps allows for the materials with the superior CMR characteristics. At the first step, epitaxial single phase precursor La1−xAyMnO3 (0.3 ≥ x > y) is formed on the single crystal substrate due to the epitaxial stabilization by the single source MOCVD (metalorganic chemical vapor deposition) using thd-complexes. The second step is the isopiestic annealing with the powder mixture determining the high concentration of the volatile oxide in the gas phase resulting in the saturation of La1−xAxMnO3 (x = y) films by the gas phase transport. The film transformations are studied with XRD and HREM. The high magnetoresistance MR and magnetotransmission MT with the linear magnetic field (H) dependence near the room temperature (dMR/dH up to 45%/T, dMT/dH up to 15%/T) are reported.

Reflection spectra, resistivity, thermopower and the Hall effect of Ca 1− x La x MnO 3 (0.03⩽ x ⩽0.12) single crystals are studied. It is shown that the optical spectra are described by the Drude model. Concentration of the charge carriers is determined to be equal to doping ∼10 21 cm −1 . In contrast to lightly hole-doped manganites, in Ca 1− x La x MnO 3 conductivity has a band character. The optical effective mass m * of electrons and effective mass of density of states of the conduction band m d * are found to be about 2 – 3 m 0 and ∼ 10 m 0 , respectively. The width of the conduction band is estimated as ∼1 eV. The revealed difference between optical effective mass and effective mass of density of states is attributed to the anisotropic dispersion law and multivalley character of the conduction band.

The magnetic, transport, and optical properties of electron-doped Ca 1− x La x MnO 3− δ single crystals with x ⩽0.12 were studied. The magnetic measurements show that in single crystals with x = 0 and 0.05 the G-type AFM phase with weak FM component is realized and in crystals with x = 0.10 and 0.12 the G- and C-type AFM phases coexist. The C-type magnetic structure arises at less concentration of La than in polycrystalline samples as a result of oxygen vacancies being additional source of electrons. Under magnetic transitions in the G- and C-type phases, resistivity and magnetoresistance of the doped single crystals have anomalies. Optical absorption in IR range indicates formation of a charge gap in crystals with x = 0.10 and 0.12 at appearance of the C-AFM and monoclinic phase with orbital/charge ordering. By comparing optical and transport properties, heterogeneous electronic state and its relation with heterogeneous magnetic state are shown.

The optical spectra (reflection and absorption) of La0.85Sr0.15MnO3 (LSM) and La0.85Ba0.15MnO3 (LBM) single crystals are studied in the infrared range, where the interaction of charge carriers with light dominates. In paramagnetic state, the small lattice polarons dominate the optical properties of LBM single crystal but in the optical spectra of LSM crystal the polarons manifest themselves weaker. The activation energy of polaron hopping Ea is determined.

Optical absorption spectra, transverse Kerr effect, resistivity and magnetoresistance of polycrystalline films La1−xSrxCoO3 (x=0.15;0.25;0.35) are studied. The temperature dependences of optical and magneto-optical properties were found to have specific features which can be caused by changes in spin state of Co3+ ions. The results obtained support the phase separation scenario in doped cobaltates. Magnetic interaction between different phases is controlled by the number of Co3+ (intermediate-spin state, S=1) ions in the orbital ordered state.

The investigation of optical and magnetooptical properties of La x MnO 3 (0.83⩽ x ⩽1.10) films revealed the changes of spectra and of electronic structure caused by the deviation from the stoichiometry and by strain in the films. Transversal Kerr effect data, temperature dependencies of magnetotransmission and magnetoresistance give the evidence for existence of charge and magnetic phase separation. The experimental results are discussed within the theoretical model of effective medium.

The charge and magnetic states of LaMnO 3 single crystal with electron doping by Ce (7%) have been studied and compared with undoped manganite and a Sr-doped compound. Extensive study including investigation of magnetic, transport properties, infrared optical absorption, electron-spin resonance, and neutron scattering have been performed. The substitution of La by donor impurity of Ce results in a partial compensation of holes induced by cation vacancies. Results are explained by charge segregation and “modulated” canted antiferromagnetic state.