307 research outputs found
Determination of exchange energies in the sawtooth spin ring {Mo75V20} by ESR
The magnetism of the polyoxometalate cluster {Mo75V20}, containing a sawtooth
ring of 10 corner-sharing triangles located on the equator of the barrel-shaped
molecule, has remained debatable since it is masked by contributions from
impurities as well as temperature-independent paramagnetism. In this article we
demonstrate the usefulness of ESR measurements since the temperature dependence
of the ESR intensity can discriminate between impurity and molecular
contributions. We determine the exchange parameters and therefore also the
low-lying spectrum of {Mo75V20}, especially the low-lying singlet states which
so far have been probed solely by specific heat measurements.Comment: 5 pages, 5 figures, submitted to PR
Композиционные силикатные краски с улучшенными технологическими сойствами
The composition of one-packing silicate paint on the basis of liquid glass modified by acrylic dispersion in number of 5%, including inactive filler in number of 15% in the form of talc and chalk, zinc oxide ranging from 5 to 9% as a hardener, and an active silica component which contents changes depending on its nature was developed. Liquid glass compositions with usage of aerosol and activated quartz sand was received. They improved characteristics and increased viability approximately to one year
Изучение свойств нитрид-, карбидкремниевого (Si[3]N[4]-SiC) композиционного материала
Materials based on silicon carbide and nitride occupy a certain segment of ceramics market due to its thermal and chemical stability, thermal conductivity and hardness. In presented report properties, composition, structure and catalytic activity of silicon nitride and silicon carbide Si[3]N[4]-SiC material have been studied. The behavior of 5% mas. Ag supported on Si[3]N[4]-SiC has been investigated in the process of gas-phase catalytic oxidation of ethylene glycol to glyoxal
Метод анализа иерархий, как метод решения проблем, возникающих при выборе информационных систем
Magnetic characterization of the frustrated three-leg ladder compound [(CuCl2tachH)3Cl]Cl2
We report the magnetic features of a new one-dimensional stack of
antiferromagnetically coupled equilateral copper(II) triangles. High-field
magnetization measurements show that the interaction between the copper
triangles is of the same order of magnitude as the intra-triangle exchange
although only coupled via hydrogen bonds. The infinite chain turns out to be an
interesting example of a frustrated cylindrical three-leg ladder with competing
intra- and inter-triangle interactions. We demonstrate that the ground state is
a spin singlet which is gaped from the triplet excitation.Comment: 6 pages, 9 figures, revised version submitted to Phys. Rev. B. More
information at http://obelix.physik.uni-osnabrueck.de/~schnack
Ag(II) as spin super-polarizer in metal fluoride clusters
Using quantum mechanical calculations, we examine magnetic (super)exchange
interactions in prototypal molecular fluoride clusters containing late
transition metals or selected lanthanides, as well as Ag(II). By referencing to
analogous species comprising closed shell Cd(II) we provide evidence that the
presence of Ag(II) may modify the magnetic properties of such systems
(including metal metal superexchange) to an unprecedented degree, specifically
both coupling sign and strength may markedly change. Remarkably, this happens
in spite of the fact that the fluoride ligand is the least susceptible to spin
polarization among all monoatomic ligands known in chemistry. Ag(II), with one
hole in its d shell, stands as spin superpolarizer, and this feature could be
exploited in spintronics and diverse molecular devices.Comment: 6 pages, 3 figures, 2 tables, and 19 pages of supplementary
informatio
Structural phase transitions and magnetic superexchange in MIAgIIF3 perovskites at high pressure
Pressure induced phase transitions of MIAgIIF3 perovskites where M = K, Rb,
Cs, have been predicted theoretically for the first time for pressures up to
100 GPa. The sequence of phase transitions for M = K and Rb consists of an
orthorhombic to monoclinic and back to orthorhombic transition, associated with
progressive bending of infinite chains of corner sharing [AgF6]4 minus
octahedra and their mutual approaching via secondary Ag...F contacts. In stark
contrast, only a single phase transition i.e. tetragonal to triclinic, is
predicted for CsAgF3, associated with substantial deformation of the Jahn
Teller-distorted first coordination sphere of AgII and association of the
infinite [AgF6]4 minus chains into a polymeric sublattice. The phase
transitions markedly decrease the coupling strength of intra-chain
antiferromagnetic superexchange in MAgF3 hosts lattices.Comment: 7 pages, 3 figures, and electronic supplement of 25 page
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