Materials Literature
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The one-exciton, one-magnon system is treated for a suitable antiferromagnetic insulator, Mn${\mathrm{F}}_{2}$. Zone-edge excitons and magnons are found to interact quite strongly. Bound states are found to exist under favorable circumstances. The line shapes of magnon sidebands of excitonic transitions are modified.…
We have extended earlier work on the Raman spectrum of quartz to both higher and lower temperatures (6-900\ifmmode^\circ\else\textdegree\fi{}K), and find evidence for the assignment of features in the 130- to ${200\ensuremath{-}\mathrm{c}\mathrm{m}}^{\ensuremath{-}1}$ region as second order. Anomalies in the temperatu…
It was recently suggested that the metal-nonmetal transition which occurs in ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ at \ensuremath{\simeq}120\ifmmode^\circ\else\textdegree\fi{}K may be of the Mott-Wigner type. Present results on the effects of pressure on the transition temperature and the conductivity of the low-tempe…
Ferroelectric properties in gadolinium molybdate are shown to originate from a new mechanism completely different from that in conventional ferroelectric materials. In this crystal the spontaneous polarization results from an elastic instability which gives rise to a spontaneous strain in the original piezoelectric pa…
With the help of the correlation-function formula given by McLennan, an expression for the viscosity tensor is obtained within the Hartree-Fock approximation using the cubic anharmonic momentum-flux operator. In the Debye approximation for phonons and with a simple expression for relaxation time, solutions are obtaine…
The weak-field magnetoresistance coefficients have been measured in niobium-doped SrTi${\mathrm{O}}_{3}$ at 4.2, 77, and 120\ifmmode^\circ\else\textdegree\fi{}K. The results at 77 and 120\ifmmode^\circ\else\textdegree\fi{}K are consistent with a conduction-band structure consisting of minima along the $〈100〉$ reciproc…
The optical density between 2400 and 7000 Å of the vapor in equilibrium with Si–Te samples containing between 10 and 100 at.% Te was measured for sample temperatures between 500° and 940°C. The partial pressures of Te2(g), pTe2, were obtained from the optical densities at 4357, 5000, and/or 5500 Å, where SiTe(g) does…
The frequencies and symmetries of the even-parity lattice vibrations of BaClF, BaBrF, and SrClF are determined by means of polarized Raman scattering from oriented single crystals. The polarizations and frequencies of the vibrations are interpreted in terms of symmetry coordinates.
The band structures of the lead salts PbS, PbSe, and PbTe have been studied by electro-optic methods. Electroabsorption and electroreflectance measurements have been made over the energy ranges 0.25 to 0.65 eV and 0.6 to 5.5 eV, respectively, using an electrolyte to produce electric fields at the surface of these mate…
Lattice vibrations in elemental crystals can possess a first-order electric moment, and thus exhibit reststrahlen (symmetry-allowed one-phonon infrared absorption), by the mechanism of displacement-induced charge redistribution (dynamic charge). By a group-theoretical investigation of the relation between symmetry and…
Abstract A new theoretical analysis is made of the elastic constants of crystalline native cellulose. Primary interatomic forces are considered in the calculation of the Young modulus in the chain direction, where we retrieve a result identical to that of Treloar. Hydrogen bonds provide the main mechanism for determin…
Measurements of the magnetization and differential susceptibility of GdAl${\mathrm{O}}_{3}$ have been made in pulsed magnetic fields in the temperature range 1.3-100\ifmmode^\circ\else\textdegree\fi{}K. It is found that GdAl${\mathrm{O}}_{3}$ is a uniaxial antiferromagnet with the easy axis of magnetization along the…
An electron-paramagnetic-resonance study of rare-earth impurities in II-VI compounds has been made. Isolated trivalent rare-earth ions are found to be substitutional for the metal ion in the zinc-blende crystals. Spectra from trivalent ions both at the isolated substitutional site and incorporated in additional unknow…
A comprehensive study of the properties of "source-free" wave fields (i.e., diffracted wave fields expressible by plane-wave expansions containing only homogeneous waves) is summarized. The theorems proved in the study are stated. A new series mode expansion for "source-free" wave fields in included.
The triple-point pressure of four grades of graphite was determined to be 103 atm (absolute). The triple-point temperature varied from one grade to another with values ranging from 4183 \ifmmode\pm\else\textpm\fi{} 10 to 4299 \ifmmode\pm\else\textpm\fi{} 25\ifmmode^\circ\else\textdegree\fi{}K. The solidus-liquidus tem…
A model of hard spheres immersed in a uniform background potential, which has been successfully applied to the calculation of atomic self-diffusion in liquid metals, is shown to give a quantitative description of the velocity of sound, the compressibility, and their temperature dependences in liquid metals of widely d…
30Beyond n, use of an asymptotic formula as discussed in Ref. 23 is suggested, which is (if adapted to the present calculations) for lines involving upperand lover-state principal quantum numbers n and e' Q p ~I 8 (e) = -5 1++ y e dy+d in the quasistatie broadening, and elect~'. m impact broadening.
Three points in Fig. They are the I point in the conduction band, and the two adjacent points along the
Abstract Relationships between the mechanical properties of electrodeposited iron and the pH of the bulk of the solution were obtained for a chloride/fluoborate plating bath. Both ultimate tensile strength and percentage elongation at fracture passed through a maximum over a narrow range of pH. Structural studies usin…
Single crystals of barite grown in this laboratory by a chemically reacted flux method have been cleaved parallel to (001) and (110) planes and the cleavage faces have been studied by multiple beam interferometry. The cleavage faces were etched in HCl and H2SO4 and the etch patterns were compared with those produced o…