Materials Literature
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Quantum phase interference and spin-parity effects are studied in biaxial molecular magnets in a magnetic field at an arbitrarily directed angle. The calculations of the ground-state tunnel splitting are performed on the basis of the instanton technique in the spin-coherent-state path-integral representation, and comp…
Results of measurements of dynamic tensile strength (“spall strength”) of aluminum single crystals are presented. In the shock-wave experiments the load duration was about 40 ns, the initial temperature was varied from 20 to 648 °C that is only 12 °C less than the melting temperature of aluminum. Under these condition…
Excitation pattern and decay kinetics of ultraviolet photoluminescence of porous silica are investigated between 4.5 and 10 eV by means of synchrotron radiation. Spectra are dominated by a 3.7 eV emission similar to the recently observed ultraviolet emission of oxidized porous Si and Si nanostructures. Emission intens…
The influence of local electronic correlations on the properties of colossal magnetoresistive manganites is investigated. To this end, a ferromagnetic two-band Kondo lattice model is supplemented with the local Coulomb repulsion missing in this model and is analyzed within dynamical mean-field theory. Results for the…
We have fabricated a (La1−xSrx) MnO3/SrTiO3 heterostructure and measured the temperature dependence of magnetization and resistivity under white light irradiation. We found that increased resistivity and a decrease of the metal-to-insulator transition temperature by 10 K occur under illumination of light at a waveleng…
A continuous CO2 laser beam was focused on a surface of hexagonal boron nitride under low nitrogen pressure, inducing a stiff radial temperature gradient, rising locally over the dissociation temperature. Boron nitride nanotubes and faceted boron nitride onions were found on the heated surface, segregated in specific…
Single-crystal Co2MnGe Heusler alloy films were epitaxially grown on GaAs (001) substrates by molecular beam epitaxy. In situ reflection high-energy electron diffraction patterns and Auger spectroscopy confirmed the high-quality growth and stoichiometry. At 5 K, a saturation magnetization of 1000 emu/cm3 was measured.…
We study quantum-classical escape-rate transitions for uniaxial and biaxial models with finite spins S=10 (such as Mn_12Ac and Fe_8) and S=100 by a direct numerical approach. At second-order transitions the level making a dominant contribution into thermally assisted tunneling changes gradually with temperature wherea…
We study strongly nonlinear disordered media using a functional method. We solve exactly the problem of a nonlinear impurity in a linear host and we obtain a Bruggeman-like formula for the effective nonlinear susceptibility. This formula reduces to the usual Bruggeman effective medium approximation in the linear case…
Neutron inelastic scattering measurements of the polar transverse optic phonon mode dispersion in the cubic relaxor $\mathrm{Pb}({\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{2/3}{)}_{0.92}{\mathrm{Ti}}_{0.08}{\mathrm{O}}_{3}$ at 500 K reveal anomalous behavior in which the optic branch appears to drop precipitously into the acou…
The theoretical strength of diamond has been calculated for the <100>, <110>, and <111> directions using a first principles approach and is found to be strongly dependent on crystallographic direction. This elastic anisotropy, found at large strains, and particularly the pronounced minimum in cohesion in the <111> dir…
A ZnO diode was fabricated by using a laser-doping technique to form a p-type ZnO layer on an n-type ZnO substrate. A zinc-phosphide compound, used as a phosphorous source, was deposited on the ZnO wafer and subjected to excimer-laser pulses. The current–voltage characteristics showed a diode characteristic between th…
Three types of triphenylmethane leuconitrile derivatives incorporating one, two, and three monoaza-15-crown-5 moieties have been designed to attain photocontrol of metal-ion complexation primarily by intramolecular electrostatic repulsion. Photochromism of the crowned triphenylmethane leuconitriles is influenced by th…
Two mononuclear copper(II) complexes with the unsymmetrical tridentate ligand 2-[((imidazol-2-ylmethylidene)amino)ethyl]pyridine (HL), [Cu(HL)(H2O)](ClO4)2.2H2O (1) and [Cu(HL)Cl2] (2), have been prepared and characterized. The X-ray analysis of 2 revealed that the copper(II) ion assumes a pentacoordinated square pyra…
The preparation, structure, and electrochemical and electrocatalytical properties of a new polyoxometalate-based organic/inorganic film, composed of cetyl pyridinum 11-molybdovanadoarsenate (CPMVA) molecules, have been studied. Cyclic potential scanning in acetone solution led to a stable CPMVA film formed on a highly…
The near-infrared CD spectrum of ytterbium complexed by DOTMA, [DOTMA = (1 R,4 R,7 R, 10 R )-α,α‘,α‘ ‘,α‘ ‘‘-tetramethyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid)] is presented. This is the first report of a near-infrared CD spectrum in solution of the f−f transitions of ytterbium in a complex whose so…
When p-type silicon is contacted to a noble metal in HF solution containing an oxidizing agent, a galvanic cell can be formed. The oxidizing agent is reduced at the metal and the semiconductor is etched. To achieve a similar effect with n-type silicon, illumination is required. On the other hand, a galvanic cell is fo…
Photochemical ligand substitution of fac-[Re(X2bpy)(CO)3(PR3)]+ (X2bpy = 4,4'-X2-2,2'-bipyridine; X = Me, H, CF3; R = OEt, Ph) with acetonitrile quantitatively gave a new class of biscarbonyl complexes, cis,trans[Re(X2bpy)(CO)2(PR3)(MeCN)]+, coordinated with four different kinds of ligands. Similarly, other biscarbony…
Hydrolysis of Si−O−Si linkages of β-cristobalite by a single H 2 O molecule is studied within the cluster approach at the DFT (B3LYP) and MP2 levels of theory. The 6-31G(d) and 6-311G(d) basis sets are used. Cluster models, including from 6 up to 14 Si atoms, of the (001) and (111) surface planes are considered. These…
We report a colorimetric method for the in situ study of electrochromic polymers based on the CIE system of colorimetry. This method is useful for the comparison of the electrochemical and optical properties of conjugated polymers, and for gaining control of the color of dual polymer electrochromic devices. Twelve ele…