Effect of the degradation of ion-exchange resins on the quality of high-purity water prepared by ion-exchange deionization

In the course of water deionization on ion-exchange filters of mixed action, charged with a mixture of KU-2×8 ch.s. cation exchanger and AV-17×8 ch.s. anion exchanger, which are ion-exchange resins of nuclear class, the water being treated is contaminated with soluble organic substances originating from degradation of the resins. Their concentration can reach 20 µg L–1, gradually decreasing to 5–6 µg L–1. Procedures were suggested for determining soluble organic substances washed out from the ion-exchange filters, including gravimetric determination of their sum in aqueous extracts from the organic ion exchangers, spectrophotometric determination in water being purified on the ion exchangers, and preconcentration of electrically charged forms of soluble organic substances by electroosmosis.     

Doping-induced temperature evolution of a helicoidal spin structure in the MnGe compound

The helicoidal magnetic structure of a MnGe compound doped with 25% Fe is studied by means of small-angle neutron scattering in a wide temperature range of 10–300 K. Analysis of the scattering-function profile demonstrates that magnetic structures inherent to both pure MnGe and its doped compounds are unstable. The doping of manganese monogermanide is revealed to lead to higher destabilization of the magnetic system. In passing from MnGe to Mn_0.75Fe_0.25Ge, the magnetic-ordering temperature T _N decreases from 130 to 95 K, respectively. It is demonstrated that, at temperatures close to 0 K, the intensity of the contribution to scattering from stable spin helices decreases and the intensity of scattering by spin helix fluctuations increases with increasing impurity-metal concentration. An increased intensity of anomalous scattering caused by spin excitations existing in the system is observed. Helicoidal fluctuations and spin excitations corresponding to low temperatures indicate the quantum nature of the instability in the doped compound. However, MnGe doping with Fe atoms has no influence on the compound’s magnetic properties at temperatures of higher than T _N. The temperature range of short-range ferromagnetic correlations is independent of concentrations and is restricted by temperatures T ranging from 175 to 300 K.     

NMR Analysis of the Magnetic Structure and Hyperfine Interactions in a FeP Binary Helimagnetic

Physics of the Solid State - An NMR analysis of 31P nuclei in metallic iron phosphide FeP has been performed both in a zero field and by sweeping the external magnetic field at several fixed...     

Electron–Hole Dimers in the Parent Phase of Quasi–2D Cuprates

Physics of the Solid State - The key feature of parent cuprates of the La2CuO4 type, in addition to their high ionic polarizability and closeness to polarization catastrophe, is identified as their...     

Optical 4<Emphasis Type="Italic">f</Emphasis>-4<Emphasis Type="Italic">f</Emphasis> transitions in multiferroic HoMnO<Subscript>3</Subscript>

In the absorption spectra of the hexagonal single-crystal manganite HoMnO₃ in the paramagnetic ferroelectric state, lines near 1.1 and 2.0 μm were observed associated with the transitions ⁵ I ₈ → ⁵ I ₆ and ⁵ I ₈ → ⁵ I ₇, respectively, within the 4f ¹⁰ configuration of the Ho³⁺ ion. At T = 80 K, to the ⁵ I ₈ → ⁵ I ₇ transition corresponds one band at 1.9 μm for both polarizations E ∥ c and E ⊥ c. As the temperature increases from 80 to 293 K, a low-energy band with a peak at 2.04 μm for E ⊥ c and a peak at 2.07 μm for E ∥ c arises associated with transitions from an excited Stark level of the ground ⁵ I ₈ multiplet to the Stark levels of the ⁵ I ₇ multiplet and with an increase in the population of the initial Stark level, the energy of which is ～100 K.     

Birthday of Vladislav Veniaminovich Malakhov

Chronicle

Birthday of Vladislav Veniaminovich Malakhov     

Sixth all-Russia conference on environmental analysis “Ekoanalitika-2006”

Chronicle

Sixth all-Russia conference on environmental analysis “Ekoanalitika-2006”     

Structure and properties of the surface alloy formed by irradiating a film/substrate system with a high-intensity electron beam

A film/substrate system has been treated with a submillisecond high-intensity electron beam. Examinations have shown that the electron-beam treatment of the film/substrate system resulted in alloying of the surface layer of the material throughout the melt which was accompanied by the formation of nanodimensional phases.     

Pseudogap phase in cuprates: Oxygen orbital moments instead of circulating currents

Circulating current loops within the cuprate unit cell are proposed to play a key role in the physics of the pseudogap phase. However, main experimental observations motivated by this sophisticated proposal and seemingly supporting the circulating current model can be explained within a simple and physically clear microscopic model. It has been argued that, instead of a well-isolated Zhang-Rice (ZR) singlet ¹ A _1g , the ground state of the hole center [CuO₄]^5? (cluster analog of Cu³⁺ ion) in cuprates should be described by a complex ¹ A _1g -^1,3 B _2g -^1,3 E _u multiplet, formed by a competition of conventional hybrid Cu 3d-O 2p $b_{1g} (\sigma ) \propto d_{x^2 - y^2 }$ state and purely oxygen nonbonding O 2p?? states with a _2g (??) and e _{ux, y} (??) symmetry. In contrast to inactive ZR singlet we arrive at several novel competing orbital and spin-orbital order parameters, e.g., Ising-like net orbital magnetic moment, orbital toroidal moment, intra-plaquette??s staggered order of Ising-like oxygen orbital magnetic moments. As a most impressive validation of the non-ZR model we explain fascinating results of recent neutron scattering measurements that revealed novel type of magnetic ordering in pseudogap phase of several hole-doped cuprates.     

The isotope effect and phase separation in (La0.5Pr0.5)0.7Ca0.3MnO3 films: Optical data

A new approach to the study of phase separation in lanthanum manganites is proposed based on the combined investigation of their optical and magnetooptical characteristics providing information about the conducting and ferromagnetic regions, respectively. Effects of the ¹⁸O isotope substitution for ¹⁶O in the epitaxial films of (La_0.5Pr_0.5)_0.7Ca_0.3MnO₃ (grown on SrTiO₃ or LaAlO₃ substrates) upon the IR absorption spectra and the equatorial Kerr effect measured in the 1.5–3.8 eV range were studied. A giant drop in the temperature of maximum resistance of the film grown on SrTiO₃ and disappearance of the metal-insulator transition in the film on LaAlO₃, observed upon the isotope exchange, are accompanied by a decrease in the contribution of free charge carriers to the absorption spectra, by the appearance of bands due to localized states, and by a decrease in magnitude of the equatorial Kerr effects. Measurements of the Kerr effect and the temperature variation of the optical transmission show evidence of the presence of ferromagnetic metal regions in the ¹⁸O-isotope-substituted (La_0.5Pr_0.5)_0.7Ca_0.3MnO₃/LaAlO₃ film at low temperatures, with a general semiconductor character of the resistivity behavior in the entire temperature range studied. Changes observed in the absorption spectra are explained based on a model of the pseudo-Jahn-Teller polar centers and phase separation. The optical and magnetooptical data show evidence of a percolation nature of the giant isotope effect in manganites.