Materials Literature
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The anisotropic magnetostriction of the cubic Laves-phase compounds RCo2 (R = Pr, Nd, Gd, Tb, Dy, Ho, and Er) has been measured from 4.2 K to above the ordering temperatures. Large magnetostrictions are observed for all compounds except GdCo2 the largest effect being in TbCo2. An attempt is made to deduce the single c…
Raman, far infrared, and electronic absorption spectra have been recorded for the [NiCl4(H2O)2]2− anion in dirubidium tetrachlorodiaquonickelate(II), Rb2NiCl4⋅2H2O. The vibrational spectra are analyzed in terms of an effective anion symmetry sufficiently low to remove all eigenstate degeneracies, while the d-electron…
A liquid crystal field-effect light valve with high-speed turn-off operation is described. The three-terminal device is symmetric in its turn-on/turn-off operation and uses digital rather than multifrequency addressing.
The magnetization of magnetite was measured with high accuracy in the temperature region of the transition. The decrease of the saturation magnetization of about 0.1% was observed on cooling. The observed changes of the apparent magnetization along various directions are quantitatively explained in terms of the orthor…
The α–β transformation of berlinite (AlPO 4 ) at 586 °C was studied by X-ray diffraction. Atomic displacements were obtained from results of least-squares refinement of data taken between room temperature and 600 °C using reflections whose intensity is unaffected by Dauphiné twinning. The results suggest a rotational…
We have carried out a comparative study of the dc conductivity in tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) and its isostructural selenium analogs TSeF-TCNQ (tetraselenafulvalene) and cis/trans-DSeDTF-TCNQ (diselenadithiafulvalene) below their metal-insulator transitions. Our study reveals the presence of…
To specify the condition for the anomalous thermal expansion due to a large spontaneous volume magnetostriction in ferromagnetic Laves phase intermetallic TFe 2 compounds, thermal expansion measurements for some TFe 2 compounds were made. The obtained results suggest that the anomaly is sensitive to the interatomic di…
An absolute gravimetric method of measuring surface and interfacial tensions of liquids by pulling a sphere through the interface is examined. The method also permits simultaneous measurement of the contact angle of the liquid on the sphere surface; this enables corrections to be made for incomplete wetting of the sol…
The system Mn 2 Sb (1- x ) As ( x ) (0≦ x ≦1) is found to be solid solutions of the Cu 2 Sb type by X-ray analysis. A magnetic phase diagram has been produced by magnetic measurments in the temperature range 80 to 1100 K. Transition from antiferromagnetic to ferrimagnetic states with increasing temperature was observe…
X-ray measurements have been carried out on paratellurite (${\mathrm{TeO}}_{2}$) at pressures up to 89 \ifmmode\pm\else\textpm\fi{} 1 kbar. Based on both single-crystal and polycrystalline data, a phase transformation from the tetragonal $P{4}_{1}{2}_{1}2 ({D}_{4}^{4})$ space group to the orthorhombic $P{2}_{1}{2}_{1}…
When acetonitrile solutions of tetrathiafulvalene [i.e., (C3S2H2)2; herein called TTF] and iodine, I2, are allowed to mix by diffusion, monoclinic crystals are formed with the approximate composition (TTF)7I5. These crystals have an electrical conductivity along the needle axis c of 300 ohm−1⋅cm−1 at room temperature.…
The magnetic interactions in Heusler alloys Pd 2 MnSn and Ni 2 MnSn have been investigated using neutron spin wave scattering. The spin wave dispersion relations along the [00ζ], [ζζ0] and [ζζζ] directions have been observed across the whole magnetic Brillouin zone. The results have been analyzed using a Heisenberg Ha…
We have studied the effects of water and defects on the Raman spectrum of fused silica. Intensities of defect lines at 604 and 490 cm−1 were found to increase with fictive temperature and to decrease with increasing OH content. The results suggest that water in the melt is preferentially trapped at the defect sites. T…
A two-parameter tight-binding theory of the electronic structure of 4:2-coordinated materials is proposed. The parameters, a covalent and a polar energy, are fitted to the optical absorption spectra. The valence energy bands and density of states are calculated. In terms of these a consistent interpretation of all the…
The exact Landau level structure of graphite has been obtained for the magnetic field parallel to the c -axis with the aid of the numerical calculation. Special emphasis is layed on the effect of the trigonal warping in band structure which has been treated approximately up to the present. The peculiar behaviour of La…
The crystal structures of a number of copper selenides have been re-examined using X-ray powder diffraction intensity data. |F 0 | values for Cu 1•8 Se at room temperature (a = 5.765 Å) are satisfied by a model based on space group Fm3m with 4 Se atoms per unit cell on the fcc sites, 5.2 Cu atoms on the tetrahedral si…
The Slater-Koster linear-combination-of-atomic-orbitals (LCAO) interpolation method is applied to fit the results of nonrelativistic augmented-plane-wave (APW) calculations at symmetry points in the Brillouin zone for several metallic transition-metal dioxides with the rutile structure, namely, ${\mathrm{RuO}}_{2}$, $…
The conduction threshold which occurs in resistor networks when a certain fraction has zero conductivity can be treated as a sort of critical point. This critical point is also relevant to mixtures of resistors with finite conductivities a and b, in the limit a<<b. A homogeneous function representation is proposed for…
The thermal diffusivity of polycrystalline BN has been measured from 100 to 800K using a 'flash' technique; published specific heat data have been used to evaluate the thermal conductivity. Over a limited temperature range the results have been confirmed by steady-state measurements. The results have been compared wit…
The thermal conductivity of composites made from epoxy-resin Epikote 828 with metal-powder fillers has been measured from 1.7 to 300K. The metals were Cu, Ag, Au, Al, Sn, Pb, stainless steel and bronze, and in almost all cases the particles were spherical or rounded. At 20K and above the thermal conductivity is indepe…