Materials Literature
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Les structures magnétiques de TMn2O5 (T = Lu, Er, Y, Ho, Tb, Nd) ont été étudiées par diffraction neutronique. Pour toutes ces terres rares, l'ordre des spins des Mn3+ et Mn4+ est hélimagnétique, avec un vecteur de propagation κ = ½ 0 τ: la maille chimique est donc doublée suivant a, et les spins d'une maille à l'autr…
The anisotropic viscoelastic and heat-conductivity properties of nematic liquid crystals offer the possibility of obtaining thermal convection with very low thresholds in homeotropic films heated from above. We present experiments on $p\ensuremath{-}\mathrm{m}\mathrm{e}\mathrm{t}\mathrm{h}\mathrm{o}\mathrm{x}\mathrm{y…
An initial oxidation process is studied on 5.59 at. % Si–Fe alloy (100) and iron (100) single crystals by the photoelectric work function combined with Auger electron spectroscopy in the low-pressure range of oxygen (10−8−10−6 Torr). A 46-V Auger peak of iron is split into two peaks (41 and 49 V) followed by an oxygen…
The thermal conductivity of cerium magnesium nitrate has been measured over the temperature range 0.2-1.5\ifmmode^\circ\else\textdegree\fi{}K. When an assumption is made that the surface of the crystal is damaged to a depth of 150 \ensuremath{\mu}m by sandblasting, the conductivity measurements are entirely described…
The specific heat of titanium sesquioxide, ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$, and the mixed system, ${\mathrm{Ti}}_{2}{\mathrm{O}}_{3}+x%$ ${\mathrm{V}}_{2}$${\mathrm{O}}_{3}$, with $x$ ranging from 1.9 to 10.3 wt% has been measured between 0.4 and 20 K. The Debye temperature at 0 K for pure ${\mathrm{Ti}}_{2}$${\…
A modified form of the Mitchell---Makinson time-dependent perturbative calculation of the surface photoelectric effect has been carried out based on a significantly improved treatment of surface-polarization charge-density variations. The approach taken allows calculation of the excitation current back into the metal…
For $T>{T}_{t}\ensuremath{\simeq}68$ \ifmmode^\circ\else\textdegree\fi{} C, V${\mathrm{O}}_{2}$ is a metal with the rutile structure. For $T<{T}_{t}$, V${\mathrm{O}}_{2}$ is a semiconductor with a monoclinic structure. We have found semiconducting energy bands for the low-temperature structure from a parametrize…
The interaction of CO with a (110) nickel surface has been investigated using a number of techniques. Auger electron spectroscopy was used to follow the chemical composition of the surface. Using LEED, two ordered chemisorbed CO structures were found to form on the clean surface at room temperature. A (2 × 1) structur…
Fowler's hypothesis commonly used to interpret results of photoemission into the vacuum has been extended to deal with the problem of internal photoemission. This leads to the empirical relation $Y\ensuremath{\propto}{(E\ensuremath{-}{E}_{t})}^{2}$ between the quantum efficiency $Y$ and the photon energy $E$, currentl…
The theory is developed for thermally stimulated currents (TSC) that flow in optically or electrically excited insulators and semiconductors in which the field is sufficiently high and the (active) region in which the free carriers are generated is sufficiently thin (e.g., reverse-biased junctions, thin films, etc.) s…
The dispersion of the Raman cross sections of several phonon modes in CdS and ZnO using a wide range of laser energies has been measured. The ${E}_{1}(\mathrm{LO})$ and multi-LO (2-LO, 3-LO and 4-LO) modes in CdS have been studied over the energy range extending from $0.45{E}_{\mathrm{ex}}$ (exciton energy) to $1.1{E}…
Infrared-reflectivity spectra have been obtained for a large number of group-IV (Ti, Zr, Hf) and group-VI (Mo, W) transition-metal dichalcogenides. Three distinct types of spectra have been identified: In Zr${\mathrm{S}}_{2}$, Hf${\mathrm{S}}_{2}$, and Hf${\mathrm{Se}}_{2}$, very strong reststrahlen with effective cha…
Uniformly oriented thin liquid-crystal layers are required for most liquid-crystal device applications and physical investigations. Usual methods for obtaining orientation rely on a substrate interface which has an orienting action on the liquid-crystal molecules. In previously described methods the orienting interfac…
The refractive-index behavior (magnitude and dispersion) of a variety of optical glasses and amorphous semiconductors is discussed within the same oscillator framework applied earlier to single-crystal refractive-index data. Apart from density differences associated with voids and inefficient packing of disordered ato…
The kinetics of vacancy production have been studied in high-purity MgO powders after irradiation by 20 MeV protons. The rate of formation of cation vacancies fits a model of interstitial-vacancy recombination. Isochronal annealing curves show that the cation vacancy is destroyed over a narrow temperature range betwee…
A macroscopic theory of surface polaritons on semi-infinite magnetic media is presented. The general nature of surface polaritons on magnetic media is discussed. In the configuration k, M 0 , and n mutually perpendicular (where k is the propagation wavevector, M 0 is the static magnetization of the medium, and n is th…
An investigation has been made of the photon pulses and the associated current pulses in the pre-onset stage of a positive point corona in air at atmospheric pressure. The transition from burst pulses to streamer pulses is discussed.
We have measured the correlation range for fluctuations of the orientational order parameter in the isotropic phase of the liquid crystal $p$-methoxy benzylidene, $p\ensuremath{-}n$ butyl aniline (MBBA). The correlation range was found to diverge as ${(T\ensuremath{-}{T}_{c}*)}^{\frac{\ensuremath{-}1}{2}}$, in agreeme…
We have measured the valence-band density of states and the energies of the core levels of crystalline and amorphous GeTe with x-ray photoemission. The density of states of the amorphous form is found to be very similar to that of the crystal. The present results indicate that the atomic orbitals primarily determine t…
Brillouin-scattering results are reported for monodomain samples of $\ensuremath{\beta}$-methyl butyl $p$ [($p$-methoxy benzylidine)amino] cinnamate in both the smectic-$A$ and -$B$ phases. For both phases theoretical predictions are confirmed concerning the number and polarizations of the propagating hypersonic waves…