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The phase transition temperatures of identically prepared BaTiO 3 polycrystalline materials (ceramics) doped with the iron group elements are investigated. The valence states and 3d electron configurations of the dopants were determined by means of magnetic susceptibility measurements. The structure stabilities depend…
Presents a pulsed NMR study on a single crystal of 2H-NbSe 2 at atmospheric pressure and under hydrostatic pressure of 21 kbar in the temperature range 4.2-273K. Analysis of Knight shift (KS) and nuclear spin-lattice relaxation (NSLR) time data in the normal state are consistent with N(E F )=2.4 states/eV spin and an…
I show that intrinsic plasmons are created in x-ray photoemission experiments on the conduction bands of simple metals. Unlike the core case, the plasmons are produced by many-body effects and are a direct consequence of electron correlation. A theory of the intrinsic plasmon production is given and a calculation of t…
By direct spatial imaging and spectral analysis of recombination luminescence we have observed in silicon (1) the drift of photoproduced excitons from the crystal surface into a strain potential well; (2) ideal-gas behavior of the strain-confined excitons in the well between 25 and 5 K; (3) a real-space condensation n…
The ordering of Fe ions in the layer crystals FexNbS2 (x ≦ 0.67) is studied as a function of composition and temperature. At the compositions x = 0.25 and 0.67 unexpected phases occur at room temperature in slowly cooled specimens. These crystals undergo order-disorder reactions on heating and in some cases the disord…
Les résultats de travaux sur la structure magnétique de MnCoSi sont présentés. Les mesures ont été effectuées sur deux échantillons obtenus par des méthodes différentes. Une transition de phase ferro-antiferromagnétique a été observée sur les deux échantillons. La température de transition montre une forte dépendance…
Thin films of polyvinylchloride (PVC) with different concentrations of Cu and Fe have been prepared using a solution growth technique. Spectrophotometric methods were employed for the estimation of the metal concentration. The metal doped PVC films were characterized using electronic spectra, infrared spectra, and ele…
In order to gain further information concerning the nature of the $d$ electrons in ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$ we have measured the polarization-dependent reflectivity and evaluated the optical constants in the range 0.7-10 eV. The $d$-electron homopolar bonding between cation pairs plays a crucial role in t…
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Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation J. H. Sinfelt, G. H. Via, F. W. Lytle; Extended x‐ray absorption fine structure (EXAFS) of suppor…
The valence force field previously obtained on α and β polymorphs of quartz is applied to the other principal crystalline forms of SiO2. A correlation is found between certain vibrations belonging to different symmetry species. The calculated frequencies of cristobalite fit the whole experimental spectra with as much…
The atomic surface structures of the close-packed faces of single crystalline cobalt in the bulk hcp and bulk fcc phases have been determined by low-energy electron diffraction. The two separate structures were monitored on a single-crystal sample cycled through the surface-transformation temperature of 450 \ifmmode\p…
The electron-paramagnetic-resonance signal that appears when Si is crushed, cleaved, or abraded is shown to be proportional to the areas of microcracks induced in the specimen. These are shown to be more prevalent than previously realized. Detailed consideration shows that a wide variety of previously inexplicable dat…
The electronic conductivity of synthetic boron-doped diamonds is studied in the temperature range 12-1300\ifmmode^\circ\else\textdegree\fi{}K. It is shown that in the low-temperature range (below 150-100\ifmmode^\circ\else\textdegree\fi{}K) the results are best interpreted in terms of variable-range hopping. An attemp…
X-ray photoelectron spectra of the valence bands and core levels for electron binding energies ranging from 0 to 45 eV, are presented for the two perovskite-type compounds BaTi${\mathrm{O}}_{3}$ and KNb${\mathrm{O}}_{3}$. Theoretical band structures and densities of states are calculated using a parametrized tight-bin…
The energy band structure of Ti${\mathrm{Se}}_{2}$, determined in the local-density approach yields a semimetal (band overlap 0.20 \ifmmode\pm\else\textpm\fi{} 0.05 eV) with holes at $\ensuremath{\Gamma}$ and electron pockets only at $L$. The dimensions of the electron pocket indicate the presence of (7-8) \ifmmode\ti…
Expressions are derived in the harmonic approximation which relate the first-order Raman and infrared spectra of a disordered solid to a common set of vibrational densities of states. The calculations assume no periodicity, and using standard approximations lead to expressions involving explicitly defined matrix eleme…
Raman-active inter-conduction-band transitions from the ${\ensuremath{\Delta}}_{1}$ to ${\ensuremath{\Delta}}_{{2}^{\ensuremath{'}}}$ bands in heavily doped $n\ensuremath{-}\mathrm{Si}$ ($n\ensuremath{\simeq}1.5\ifmmode\times\else\texttimes\fi{}{10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$) interfere with the zone-cent…
Excitation spectra of the 4.44-eV intrinsic luminescence in a single crystal of Ca${\mathrm{F}}_{2}$ at liquid-nitrogen temperature was measured using synchrotron radiation in the x-ray region. The intrinsic luminescence at 4.44 eV is due to self-trapped exciton recombination. The intensity of the emitted uv light was…
Abstract When metals are subjected to stress at temperatures in excess of about one third of their melting temperature, it is found that they deform continuously and that they can sustain the stress for a limited time referred to as the rupture life. Constitutive equations are proposed which describe the macroscopic b…