Metastable ionic cubic structure I clathrate hydrate formed with tetra-n-butylammonium bromide

1. Download : Download high-res image (143KB)
2. Download : Download full-size image

     

Observation of Persistent Currents in Finely Dispersed Pyrolytic Graphite

The trapped magnetic flux in the finely ground pyrolytic graphite sample annealed at 670 K in air has been observed. Flux trapping occurs on cooling of the sample from room temperature to 10 K in a magnetic field of 1 T. The magnitude and sign of the induced trapped moment remain unchanged when the applied magnetic field is varied within ±1 T at T K. The trapped magnetic flux is manifested in the displacement of the magnetization curve relative to that of the sample cooled in zero field. Displacement magnitude gradually decreases with the temperature increase up to 350 K, not reaching zero. The set of experimental observations probably reflects the presence in the sample of a granular high-temperature superconducting phase.     

Classical Density Functional Theory Approach to the Vibrational Properties and Lattice Specific Heat of a Quasi-One-Dimensional Antiferromagnet KFeSe2

JETP Letters - We have performed ab initio calculations of vibrational properties of KFeSe2 compound utilizing density functional theory. Total and element specific phonon densities of states have...     

The Spectral and Magnetic Properties of Er3+ and Yb3+ Ions in Y2Ti2O7 Crystals with a Pyrochlore Structure

Physics of the Solid State - Cubic Y2Ti2O7 single crystals doped with Er3+ or Yb3+ ions have been studied by the methods of electron spin resonance (ESR) and selective laser spectroscopy. ESR...     

Chiral recognition of N-thiophosphorylated thioureas via nickel(ii) coordination assisted by 4-dimethylaminopyridine

Nickel(ii) complexes were synthesized using chiral N-thiophosphorylated thioureas as the starting compounds and 4-dimethylaminopyridine as a co-ligand. The reaction with racemic thiourea afforded homochiral complexes due to the distortion of the nickel coordination. The unsaturated coordination sphere of nickel ions results in the formation of supramolecular homochiral 1D chains in the crystal through steric key—lock interactions between adjacent molecules. Conformational flexibility of the ligands is responsible for disorder of molecules in the crystals and the occurrence of polymorphs.

     

Structure and Metastability of MF<Subscript>2</Subscript> (M = Ca,Sr, Ba) Fine Powders Mechanochemically Doped with Er<Superscript>3+</Superscript> Ions

In the paper thermal treatment investigations of the MF₂ (M = Ca, Sr, Ba) fine powders mechanochemically doped with Er³⁺ ions using electron paramagnetic resonance and X-ray diffraction are presented. It is shown that the prepared samples are found in the nonequilibrium metastable state characterized by the high concentration of the cationic vacancies and prevalence of the cubic symmetry-doped Er³⁺ ion centers. Vacancies formed when the deformation exceeds the elastic limit serve both as the means for a nonlocal charge compensation and a route for mechanically activated diffusion. Annealing brings the powders to the ground state with the most of the vacancies healed and the trigonal symmetry of the impurity Er³⁺ centers in SrF₂ and BaF₂ due to the local compensation by the interstitial fluorine ion.     

Impact of Impurity Phases and Superstoichiometric Iron on the Critical Temperature of Iron Chalcogenides

JETP Letters - The results of transport and magnetic measurements of iron chalcogenide crystals are analyzed taking into account the data of the chemical composition and impurity phases obtained by...     

Advances in the Study of Gas Hydrates by Dielectric Spectroscopy

The influence of kinetic hydrate inhibitors on the process of natural gas hydrate nucleation was studied using the method of dielectric spectroscopy. The processes of gas hydrate formation and decomposition were monitored using the temperature dependence of the real component of the dielectric constant ε′(T). Analysis of the relaxation times τ and activation energy ΔE of the dielectric relaxation process revealed the inhibitor was involved in hydrogen bonding and the disruption of the local structures of water molecules.     

Coherent X-ray diffraction imaging of nanoengineered polymeric capsules

For the first time, nanoengineered polymeric capsules and their architecture have been studied with coherent X-ray diffraction imaging technique. The use of coherent X-ray diffraction imaging technique allowed us to analyze the samples immersed in a liquid. We report about the significant difference between polymeric capsule architectures under dry and liquid conditions.     

Femtosecond Optical and Magneto-Optical Spectroscopy Study of Magnetic and Electronic Inhomogeneities in a Pd0.94Fe0.06 Thin Film

The results of a femtosecond optical and magneto-optical spectroscopy study of a thin epitaxial film of a low-temperature magnetically soft Pd_0.94Fe_0.06 alloy on a ({dy001})-MgO substrate are reported. The photoinduced demagnetization and magnetization recovery times are determined. The latter increases critically at approaching the ferromagnetic ordering temperature T_C = 190 K from below. It is shown that the reflectivity dynamics after a photoexcitation pulse evolves from a two-exponential in the paramagnetic phase to a four-component at 80 K < T < T_C, simplifying to a three-component at T < 50 K. According to our interpretation, such an evolution, along with the manifestation of an additional increasing component in the magnetic response at 80 K < T < T_C, indicates a magnetic and electronic inhomogeneity of the film associated with the distribution of local iron concentrations. The fraction of small-scale inclusions of the paramagnetic phase is estimated as ≈10 vol %.