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Results of calculations of the electronic structure and studies of the optical properties of the Mn3Al compound in the two-phase crystalline state are reported. The calculated densities of electron states are determined by the wide (~8 eV) 3d band of Mn atoms; the Fermi level is localized within the range of high densities of states. The nature of quantum light absorption is discussed based on the comparison of experimental and theoretical spectra of the interband optical conductivity. It is shown that the calculated structure of energy bands of the compound allows us to qualitatively interpret the frequency dispersion of this spectral parameter. [ABSTRACT FROM AUTHOR]

The structure and optical properties of the Mn2FeAl Heusler alloy have been investigated. It is shown that the alloy crystallizes into a structure of the β-Mn type. The behavior of the optical conductivity of the alloy, which is anomalous for metallic systems (namely, the absence of a contribution from the intraband absorption and the presence of the intensive interband absorption), is observed in the IR spectral range. It is shown that this behavior is due to the following peculiarities of the electronic structure: the Fermi level is located in the region of a high density of states formed by the d states of Mn and Fe atoms. [ABSTRACT FROM AUTHOR]

We report on the results of analysis of magnetic properties and electronic structure, which were obtained by self-consistent ab initio spin-polarized calculations, as well as experimentally determined optical properties of cobalt-based intermetallic compounds YCo3, Y2Co7, and LaCo5. Optical characteristics were measured using ellipsometry in a wide spectral interval. The mechanism of quantum absorption of light in these materials is considered based on comparative analysis of experimental and theoretical spectra of interband optical conduction. Analysis of the crystalline structure and the resultant magnetic, electronic, and optical characteristics revealed peculiarities in the variation of physical properties. which appeared upon an increase in the cobalt content in the intermetallides. [ABSTRACT FROM AUTHOR]

The optical properties of bulk AuCu3-type ordered superconducting binary compounds ScGa3 and LuGa3 have been experimentally investigated for the first time in the wide spectral range and explained in terms of the band structure. First-principles calculations of electronic densities of states and optical conductivities are performed within the framework of LSDA+U method using the LMTO-ASA software package. The measured dielectric functions spectra for both materials exhibit a strong absorption region above ∼ 1 eV, which are in a reasonable agreement with the calculated metal-like energy structures of compounds. Features of quantum light absorption are discussed on the basis of a comparative analysis of experimental and theoretical spectra of interband optical conductivity. Plasma and relaxation frequencies of conduction electrons are determined. [ABSTRACT FROM AUTHOR]

The phenomenon of percolative charge transport on an electrified surface during adsorption of an electrically conducting phase on a dielectric substrate has been considered for the first time. The influence of the adsorption kinetics and nucleation on the formation of percolation clusters ensuring a decrease of the charge with its subsequent neutralization has been studied. It has been established that percolation transitions play a determining role in the stability of an electric charge accumulated on a dielectric surface. An increase in the rate of spontaneous nucleation and initial surface coverage with an electrically conducting phase leads to a decrease in the duration of the percolation transition. [ABSTRACT FROM AUTHOR]

Herein, we report unusual magnetic behavior in arc melted bulk stoichiometric Fe3Al alloy with a D03 structure. The temperature variation in the magnetization measurements revealed two transitions, i.e. one at ∼763 K and another at ∼830 K. Below 763 K, it exhibits ferromagnetic ordering and the nature of the transition is second order. However, the second transition is more complex and detailed analysis of the magnetic data suggested the coexistence of ferromagnetic and paramagnetic phases (two-phase: α + D03/α + B2) and structural transitions triggered by temperature. We observed dual peaks in the magnetic entropy change curve, in accordance with the magnetization results, which corroborate the occurrence of a two-phase system. We believe that the concurrent magnetic ordering and the complex two-phase are associated with the evolution of short-range ordered magnetic clusters having a magnetic moment of ∼103μB in the host matrix. A cluster hypothesis is proposed to explain the observed intricate magnetic behavior of this alloy at high temperature. The estimated critical exponents using a modified Arrott plot, Kouvel–Fisher plot and critical isotherm analysis lie in between the 3D-Heisenberg and 3D-Ising model, indicating a short-range interaction and magnetic inhomogeneity, which again are consistent with the magnetization results. The obtained critical exponents follow the universal scaling behavior, which indicates the renormalization of interactions around the magnetic ordering transition (TC). Despite the obvious larger thermal entropy at very high temperature, our synthesized Fe3Al alloy showed enhanced magnetic entropy changes. The obtained magnetic entropy change for binary Fe3Al alloy shows twice the value of that of other binary/ternary Fe-based alloys. [ABSTRACT FROM AUTHOR]

The optical properties of binary GdFe2 and LuFe2 compounds are studied by the ellipsometric method in the 0.22–17 μm spectral range. A number of spectral and electronic characteristics are determined. The experimental dependences of optical conductivity in the light quantum absorption region are interpreted based on previously published calculations of electronic states densities. [ABSTRACT FROM AUTHOR]

Ellipsometric investigations of the optical properties of Ru2Ge3 and Ru2Sn3 intermetallic compounds are carried out in the wavelength range from 0.22 to 15 μm. The nature of interband light absorption is analyzed based on a comparative analysis of the experimental and theoretical frequency dependences of an optical conductivity. The obtained results confirm the existence of energy gaps at the Fermi level in the electronic spectra of these materials predicted earlier by the band-structure calculations. [ABSTRACT FROM AUTHOR]

The noise generated by different ferrofluid samples when probed by the fiber-optic method has been investigated. It is shown that switching on a magnetic field significantly increases the noise, which is presumably related to fluctuations accompanying the process of aggregate formation. The dependences of the rms noise on the field strength and probe-light intensity have been experimentally determined. A slow decrease in the rms noise after switching off the magnetic field has been found, which indicates relaxation of the aggregates formed by the field. [ABSTRACT FROM AUTHOR]