STRUCTURE,MAGNETIC, AND MAGNETOCALORIC PROPERTIES OF SUBMICRONIC YTTRIUM IRON GARNET PARTICLES

Journal of Structural Chemistry - Scanning electron microscopy, X-ray diffraction, Raman and Mössbauer spectroscopies, field and temperature dependences of magnetic saturation and...     

Mössbauer study of new functional metal/polymer nanocomposites with spatially oriented FeGa particles

Mössbauer spectroscopy has been applied to study the structure and magnetostriction interdependence of metall/polymer composites with spatially oriented FeGa particles in a polymer matrix. Composites were synthesized combining modified polyurethane with nanocrystalline mechanosynthesized particles of magnetostrictive FeGa composition through polymerization to achieve a considerable magnetostrictive response. To increase magnetoelastic effects a spatial particle arrangement in the polymer matrix was generated. The magnetostrictive composition of the mechanosynthesized particles has been determined by Mössbauer spectroscopy, X-ray diffraction and TEM at different stages of ball milling. The microstructure of the composites via the particle orientation in the polymer has been researched by SEM and Conversion Mössbauer spectroscopy with the registration of resonant X-rays. The spatial particle inhomogeneity and magnetic anisotropy have been analyzed in order to reveal the factors determining the functional properties of the manufactured composites. Three-fold enhancement of the magnetostrictive response for FeGa/polyurethane composites with non-standard magnetic anisotropy has been demonstrated.     

Formation of x-ray images by means of thermal action of a light beam on the surface of a diffracting crystal

The results of experimental investigations of the formation of the spatial structure of x-ray diffraction beams (x-ray images) from the KDP crystal surface under its illumination by a light beam spatially modulated in intensity are presented. A simulation of the x-ray image, depending on the parameters of the diffraction peak of a crystal and on the conditions of the creation of a temperature deformation field at its surface, has been carried out.     

Lower concentration limit of carbon filtration combustion

For mixtures of carbon materials and an inert filler, dependences of the characteristics of the filtration combustion wave on the gaseous oxidizer supply rate at a fuel content in the mixture of less than 7 wt % were obtained. The existence of a lower concentration limit for a steady-state filtration combustion wave was established. It was demonstrated that at a given intensity of heat loss, the concentration limits are determined by the reactivity of the carbon material and the oxidizer supply rate. At the effective coefficient of heat loss α = 8 W/(m² K), effective conductivity of mixture material λ = 2 W/(m K), and air supply rate G = 0.1 m/s, the lowest fraction of carbon in the mixture at which combustion is still possible was 4.5 wt % for carbon-carbon composite, 2.5 wt % for activated birch coal, and 2.0 wt % for birch coal, the most reactive kind of carbon.     

Thermally induced adjustment of the parameters of X-ray diffraction peaks from crystals

The effect of nonuniform thermal action of a light beam on the parameters of a diffraction peak for a calcite crystal is studied. It is shown that the spatial intensity distribution in an X-ray beam can be corrected by controlling the thermally induced mismatch between Bragg reflections from local areas in a crystal.     

Terahertz spectroscopy of quantum-well narrow-bandgap HgTe/CdTe-based heterostructures

The energy spectra of quantum-well narrow-bandgap Hg_{1 ? y} Cd _y Te/Cd _x Hg_{1 ? x} Te heterostructures have been studied. The dependences of the effective cyclotron mass on the density (in classical magnetic fields) and the transition energy (in quantizing fields) have been obtained from the cyclotron resonance measurements. These dependences confirm the near-linear dispersion law for the electrons with small mass at the band bottom (the minimum cyclotron mass measured is 0.003 m ₀). The interband photoconductivity of the CdHgTe-based structures with the long-wavelength photoresponse edge lower than 6 meV has been demonstrated.     

Effects of the Electron—Electron Interaction in the Magneto-Absorption Spectra of HgTe/CdHgTe Quantum Wells with an Inverted Band Structure

JETP Letters - Magneto-absorption in HgTe/CdHgTe quantum wells with an inverted band structure in magnetic fields up to 30 T has been studied. It has been shown that the positions of...     

Probing States of a Double Acceptor in CdHgTe Heterostructures via Optical Gating

JETP Letters - Photoconductivity spectra in a HgTe/CdHgTe double quantum well with a normal band structure have been studied. Photosensitivity bands associated with the ionization of a mercury...