Analysis of crystallographic and structural data of polymeric FeM (M = transition metals, lanthanides) complexes

This review covers crystallographic and structural data for almost fifty polymeric FeM complexes (M = transition Cu, Ag, Au, Mo, W, Mn, Co, Ni and Pt and lanthanide elements Sm, Er and Yb) where iron is involved in polymeric chains. The complexes are for the most part yellow or black, but there are complexes of brown, orange, red, purple, blue and green colour. The complexes crystallized in the monoclinic (by far prevails), triclinic, tetragonal, orthorhombic, trigonal, hexagonal and rhombohedral crystal classes. The iron atoms are found in oxidation states 0, +2 and +3, of which +3 by far prevails. The inner coordination spheres about the Fe(0) atom are tetrahedral (FeC₄) or sandwiched (FeC₁₀), Fe(II) atoms are six-coordinated, and Fe(III) are six or even seven-coordinated. The inner coordination about M atoms range from four- through six- to eight-coordinated. The shortest Fe-Fe, Fe-M (transition) and Fe-M (lanthanide) and M-M separations are: 8.08 Å, 3.033 Å for Fe-Cu, 3.010 Å for Fe-Yb and 2.505 Å for Mo-Mo.     

The asymptotics of the solution to the Neumann spectral problem in a domain of the “dense-comb” type

Convergence theorems and asymptotic estimates (as ε → 0) are proved for the eigenvalues and the eigenfunctions of the Neumann problem in a dense singular junction Ω _ɛ of a domain Ω₀ and a large number N of thin cylinders with thickness of order ε=lN⁻¹, where l is the total length of common boundaries for Ω₀ and the cylinders in question. Bibliography: 27 titles. We dedicate the present paper to Olga Arsenievna Oleinik, as a symbol of our deep respect and gratitude Translated from Trudy Seminara imeni I G. Petrovskogo, No. 19. pp. 000-000. 0000.     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

The influence of hydrostatic pressure on Raman spectra of TIS and TlInSe2

First order Raman spectra of TIS and TlInSe₂ single crystals excited with 1.064μm line of the continuously operated YAG: Nd³⁺ laser have been investigated in equilibrium conditions under various hydrostatic pressures up to 1.08 × 10⁹ and 7.06 × 10⁸ Pa, respectively. Mode parameters γ_j = (1/ν_j)(dν_j/dP) were determined for all the Raman bands observed. Comparison of a set of these parameters in both crystals showed that the character of binding interatomic forces in these crystals appeared to be similar. For both crystals the intensity of Raman bands decreased with increasing the pressure.     

The determination of electron mean free paths in solids by depth and angular dependences of inelastically scattered electron spectra

A technique is presented of electron mean free path determination in solids using the spectra of backscattered electrons. The mean free path without energy loss (λ₀) in Ge, and the mean free paths for excitation of volume (λ_v) and surface (λ_s) plasmons in Al, are determined in the electron energy range E₀ = 0.1–10 kev. The depth d_s of surface plasmon localization is estimated for Al.     

Effect of substitution-type disorder in GaS1-xSex layer solid solutions on Raman scattering spectra

An experimental study has been carried out to investigate Raman scattering spectra of GaS_1-xSe_x solid solutions in which a one-dimensional localization of interlayer mode due to a disorder in the layer stacking was observed.     

High temperature (T>300 K) light emitting diodes for 8–12 μm spectral range

Contrary to conventional light emitting diodes for visible and very near infrared utilizing interband (ω>E_g) luminescence, the longer infrared emitting diodes (LIREDs) we describe here utilize intraband (ω<E_g) electron transitions and emit beyond the fundamental absorption range of the material used. Made of indirect band gap semiconductors (like Ge, Si) and, therefore, free from the Auger recombination impact, LIREDs efficiently operate at higher temperatures (T>300 K) in the longer wavelength atmospheric window (8–12 μm). Electrically modulated power emitted is comparable to that for black body sources whereas shorter rise–fall times are due to recombination processes (200 μs) and not dependent on pixel thermal mass and thermal conduction. LIREDs can be made of different semiconductor structures provided the controllable modulation of free carrier concentration in the device base is achieved. The main parameters of Ge based LIREDs under injection mode are reported.     

Optical and Structural Phenomena at Multipulse Interference Femtosecond Laser Fabrication of Metasurfaces on a Thin Film of Amorphous Silicon

JETP Letters - The spatial dependence of the differential conductivity of ultrathin Pb films deposited on the Si(111)7 × 7 surface has been studied by low-temperature scanning tunneling...