Materials Literature
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In this paper, the hyperfine quadrupole interaction at the Zr-Ti site of (PZT) polycrystalline samples is studied for the first time. Powders for x = 0, 0.1, 0.2, 0.4, 0.6, 0.8, 0.9 and 1 were prepared and characterized by XRD. The lattice constants and space groups were obtained as functions of Ti concentration. PAC…
The temperature dependence of the acoustic dispersion relation, $\ensuremath{\Omega}(Q,T)$, has been determined across the liquid-glass transition in o-terphenyl using inelastic x-ray scattering in the $1--6{\mathrm{nm}}^{\ensuremath{-}1}$ momentum transfer ( $Q$) range. From this the infinite frequency sound velocity…
Resistance measurements in the ``normal'' state of $(\mathrm{TMTSF}{)}_{2}{\mathrm{PF}}_{6}$ under pressure for different magnetic field orientations show striking features below 5 K. We observe metallic behavior $(\frac{\mathrm{dR}}{\mathrm{dT}}>0)$ when the field is aligned along the intermolecular tunneling dire…
A microscopical model is proposed, describing the origin and properties of three closely spaced zero-phonon lines observed in the green Cu band in ZnO:Cu crystals labelled and . These excitations are known to be formed by a charge-transfer reaction with hole bound states. These lines are shown to originate from an int…
Experiments in which the Raman linewidth was measured as a function of temperature (7-1183 K) and pressure (0-400 bar) were performed on the (111) and (100) planes of single crystals of the cubic anti-fluorite . The temperature dependence of the lattice constant was determined by x-ray diffraction (11-295 K). From the…
The stability of the $\ensuremath{\epsilon}$ phase of zirconium hydride is studied using the pseudopotential plane wave method. The fluorite structure is mechanically unstable with respect to a tetragonal distortion. However, the minimum corresponding to $c>a$ is almost degenerate in energy with that for $c<a$.…
Taking into account the bilinear coupling between the tunneling protons and the displacements of the electron shells of the surrounding ${\mathrm{PO}}_{4}$ groups, we present a new model of hydrogen-bonded ferroelectrics. The model is an extension of both the tunneling model and the nonlinear polarizability model and…
We have made ferroelectric memory capacitors by depositing a SrBi2Ta2O9 thin film on a Si substrate separated by an ultrathin buffer layer of silicon nitride film. The hysteresis in the capacitance–voltage curves suggests a sizable memory window of 2 V with a programming voltage swing of ±7 V. The switching time is es…
Using first principles variable cell shape molecular dynamics, we predict a new structure for silica. This structure results from annealing $\ensuremath{\alpha}$-quartz at pressures near a major phonon instability. The new phase is obtained by rotations of ${\mathrm{SiO}}_{4}$ tetrahedra producing edge-sharing ${\math…
We extended the sensitivity of fluorescence polarization anisotropy measurements to the single molecule level by studying the polarization response of single fluorophores rapidly rotating in liquid. Comparison with a simple model calculation allows us to obtain information on the hindered motion as well as on the rota…
Computer simulations suggest that ultrathin metal wires should develop exotic, non-crystalline stable atomic structures, once their diameter decreases below a critical size of the order of a few atomic spacings. The new structures, whose details depend upon the material and the wire thickness, may be dominated by icos…
Photocrystallization of amorphous selenium (a-Se) films under illumination by polarized light with 632.8 or 647.1 nm wavelength has been studied by Raman spectroscopy. Preferential orientation of trigonal crystalline, selenium (t-Se) obtained as a result of photocrystallization has been observed, threefold c axis of t…
The magnetoresistance (MR) associated with domain boundaries has been investigated in microfabricated bcc Fe (0.65 to 20 $μ$m linewidth) wires with controlled stripe domains. Domain configurations have been characterized using magnetic force microscopy. MR measurements as a function of field angle, temperature and dom…
The effect of domain walls on electron transport has been investigated in microfabricated Fe wires (0.65 to 20 $μm$ linewidths) with controlled stripe domains. Magnetoresistance (MR) measurements as a function of domain wall density, temperature and the angle of the applied field are used to determine the low field MR…
Long-range magnetic ordering in R_2 Ba Ni O_5 (R=magnetic rare earth) quasi-1-dimensional mixed-spin antiferromagnets is described by a simple mean-field model that is based on the intrinsic staggered magnetization function of isolated Haldane spin chains for the Ni-subsystem, and single-ion magnetization functions fo…
Linear-chain nickelates with the composition (Nd_x Y_{1-x})_2 Ba Ni O_5 (x=1, x=0.75, x=0.5, and x=0.25) are studied in a series of neutron scattering experiments. Powder diffraction is used to determine the temperature dependence of the magnetic structure in all four systems. Single-crystal inelastic neutron scatteri…
Numerical simulations were performed to predict the performance of microwave plasma reactors with various reactor geometries. The simulations include the calculation of the electric field distribution using the finite integration theory and the determination of the plasma density distribution based on a breakdown fiel…
The conditions for the self-organized formation of ordered hexagonal structures in anodic alumina were investigated for both oxalic and sulfuric acid as an electrolyte. Highly ordered pore arrays were obtained for oxidation in both acids. The size of the ordered domains depends strongly on the anodizing voltage. This…
The heat capacities of (NH4)2PbCl6 and (ND4)2PbCl6 were measured at temperatures between 13 K and 300 K. A gradual phase transition was found at 77.8±0.3 K for (NH4)2PbCl6 with an associated transition entropy of 3.0 J K−1 mol−1. The transition temperature shifted to 81.0±0.3 K in (ND4)2PbCl6. A sharp first order tran…
We report an experimental result of the thermally induced morphological transition from lamellar to gyroid phase in a binary blend of polystyrene-block-polyisoprene (SI) diblock copolymers. Two SI copolymers employed in this study have almost the same molecular weights but different volume fractions of polystyrene (PS…