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

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