Influence of Nonstoichiometry on the Magnetic Properties of CeFe2:Mn Alloys

JETP Letters - Experimental dependences of the spontaneous magnetic moment per 3d atom on the impurity concentration for doped CeFe2:Mn alloys are surprising. The concentration dependences of the...     

Electronic structure and chemical bonding in bismuth sesquioxide polymorphs

The electronic structure of the α-Bi₂O₃, Β-Bi₂O₃, and γ-Bi₂O₃ phases was investigated by the ab initio self-consistent LMTO method in a tight binding approximation and by the semiempirical Hückel method. The total and partial densities of states and Mulliken overlap populations were obtained. The stability of bismuth oxide polymorphs is discussed based on the results of the total energy calculations for crystals. An analysis of chemical bonding shows that the Bi-O interaction plays the leading role. The Bi-Bi metallic bond is absent. Mechanisms of oxygen ion migration and possible stabilization of the structure of the superionic conductor δ-Bi₂O₃ are discussed.     

Optical Properties of FeGe2 Single Crystal

Physics of the Solid State - The reflection spectra of FeGe2 single crystal in a wide spectral region and in the temperature range from 80 to 310 K are studied. The energy of plasma oscillations,...     

Genesis of the electronic spectrum and magnetic properties of a high-temperature phase of nonstoichiometric strontium ferrite SrFeO<Subscript>3–δ</Subscript> (0 ≤ δ ≤ 0.5)

The genesis of the electronic spectrum and magnetic properties of a high-temperature cubic phase of SrFeO_3–δ with the disordered distribution of oxygen vacancies under the variation of their concentration has been studied in the coherent-potential approximation within the LDA + U formalism. Experimental tendencies of the fundamental electron-energy and magnetic characteristics in SrFeO_3–δ under the variation of oxygen nonstoichiometry within the homogeneity region, 0 ≤ δ ≤ 0.5, have been described.     

Oxide ion conductors of the BIMEVOX family: Synthesis, structure, and conductivity

The synthesis, stable existence regions, structure, and migration characteristics of complex oxides of the BIMEVOX family were studied experimentally and theoretically. The temperature, composition, and oxygen partial pressure dependences of the conductivity of the samples obtained were determined. The contribution of oxide ion transport decreased as the temperature and oxygen partial pressure lowered. Quantum-chemical calculations of β-Bi₄V₂O₁₁ and γ-Bi₄V₂O₁₁ were performed to analyze the relative stabilities of the phases and the influence of dopants.     

Positive magnetoresistivity of Fe0.95Co0.05Ge2 single crystals inside the region of a magnetic phase transition

We report on the detection of two narrow peaks of positive magnetoresistivity in the temperature dependence of the magnetoresistivity of a Fe_0.95Co_0.05Ge₂ single crystal in the vicinity of a “smeared” first-order phase transition. The position of these peaks correlates with the position of singularities in the temperature dependence of the temperature derivative of the electrical resistivity and magnetic susceptibility. We show that these singularities in the transport and magnetic properties are, probably due to the presence of two percolation transitions with temperature in the magnetic subsystem of the crystal. Zh. éksp. Teor. Fiz. 112, 690–697 (August 1997)     

Electronic structure of rutile simultaneously doped with carbon and nitrogen atoms in the coherent potential approximation

The coherent potential method has been used for calculating the electronic structure and magnetic properties of rutile with a disordered arrangement of impurity carbon and nitrogen atoms in the oxygen sublattice: TiO_{2 ? x ? y} C _x N _y , x(y) = 0, 0.03, and 0.06. The tendencies to changes in the magnetic moment and photocatalytic activity with variations in the carbon-nitrogen composition of codoped rutile have been analyzed using the obtained data.     

Investigation of the influence of nonstoichiometry and doping with carbon and nitrogen on the electronic spectrum of rutile by the coherent potential method

The electronic spectra and magnetic properties of rutile (TiO₂), nonstoichiometric rutile (TiO_{2 ? δ}), and stoichiometric and nonstoichiometric rutiles doped with carbon or nitrogen (TiO_{2 ? y ? δ}C _y and TiO_{2 ? y ? δ}N _y , y(δ) = 0, 0.03, 0.06) have been calculated using the coherent potential method. The used method of investigation has made it possible for the first time to calculate the disordered arrangement of impurity atoms and vacancies in the oxygen sublattice with their arbitrary concentration. The changes in the electronic spectrum and magnetic properties with variations in the concentration of dopants have been investigated. The possible photocatalytic activity of considered compositions has been analyzed.     

2,3,5-Trichlorocyclopent-2-enone derivatives in the Friedel–Crafts reaction with methoxybenzenes and the anticancer activity of the products

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Elastic properties of La<Subscript>0.82</Subscript>Ca<Subscript>0.18</Subscript>MnO<Subscript>3</Subscript> single crystal

The temperature dependences of the velocity of longitudinal sound waves and the internal friction in a La_0.82Ca_0.18MnO₃ single crystal with the Curie temperature T _C = 181 K have been studied. As temperature decreases, the single crystal is shown to undergo the transition from the pseudocubic O* to the Jahn–Teller O’ phase at T ~ 254 K and the reverse transition from O’ to O* phase at T ~ 84 K. The velocity of sound and the internal friction in the O’ phase are found to be significantly smaller than those in the O* phase.