Materials Literature
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Mass-selected carbon ion beam deposition (MSIBD) was used to demonstrate that the diameter of a carbon nanotube could be as small as 0.4 nm, the theoretical limit predicted but never experimentally reached so far. The deposition was performed at an elevated temperature much lower than the high temperatures (800–1000 °…
The rate for cross slip of screw dislocations during annihilation of screw dipoles in copper is determined by molecular dynamics simulations. The temperature dependence of the rate is seen to obey an Arrhenius behavior in the investigated temperature range: 225-375 K. The activation energy and the effective attempt fr…
Cold-pressed powder compacts of CrO2 show large negative magnetoresistance (MR) due to intergranular tunneling. Powder compacts made from needle-shaped nanoparticles exhibit MR of about 28% at 5 K. Temperature dependence of the resistivity indicates that the Coulomb blockade intergranular tunneling is responsible for…
The magnetic anisotropy of epitaxial colossal magnetoresistance films on SrTiO3 substrates is dominated by the strain or magnetocrystalline anisotropy depending on the orientation of the film. While the magnetic anisotropy of (001) films is determined by magnetocrystalline anisotropy, that of (110) films is determined…
Using density-functional theory we identify a new low-energy structure for GaAs(001) in an As-poor environment. The discovered geometry is qualitatively different from the usual surface-dimer based reconstructions of III-V semiconductor (001) surfaces. The stability of the new structure, which has a c(8x2) periodicity…
A neutron scattering study of the Mott-Hubbard insulator ${\mathrm{LaTiO}}_{3}$ ( ${T}_{N}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}132\phantom{\rule{0ex}{0ex}}\mathrm{K}$) reveals a spin wave spectrum that is well described by a nearest-neighbor superexchange constant $J\phantom{\rule{0ex}{0ex}}=\phantom{\ru…
Neutron scattering has been used to study the nature of the ferromagnetic transition in a single crystal of the perovskite La0. 7Ca0.3MnO3. Diffuse scattering from lattice polarons develops as the Curie temperature is approached from below, along with short range polaron correlations that are consistent with stripe fo…
The temperature variation of the resistivity $\ensuremath{\rho}$ and specific heat $C$ have been measured for prototypical half-metallic ferromagnets, ${R}_{0.6}\mathrm{Sr}{}_{0.4}{\mathrm{MnO}}_{3}$, by controlling the one-electron bandwidth $W$. We have found variations in the temperature scalings of $\ensuremath{\r…
Theory of electrical spin injection from a ferromagnetic (FM) metal into a normal (N) conductor is presented. We show that tunnel contacts (T) can dramatically increase spin injection and solve the problem of the mismatch in the conductivities of a FM metal and a semiconductor microstructure. We also present explicit…
The influence of a c(2x2) ordered interface alloy of 3d transition metals at the ferromagnet/nonmagnet interface on interlayer exchange coupling (IXC), the formation of quantum well states (QWS) and the phenomenon of Giant MagnetoResistance is investigated. We obtained a strong dependence of IXC on interface alloy for…
A recent letter by Xue et al. (PRL v.83, 1235 ('99)) reports a Fermi-Liquid (FL) angle resolved photoemission (ARPES) lineshape for quasi one-dimensional Li0.9Mo6O17, contradicting our report (PRL v.82, 2540 ('99)) of a non-FL lineshape in this material. Xue et al. attributed the difference to the improved angle resol…
We present a theory of spin and orbital states in Mott insulator LaTiO3. The spin-orbital superexchange interaction between d(1)(t(2g)) ions in cubic crystal suffers from a pathological degeneracy of orbital states at the classical level. Quantum effects remove this degeneracy and result in the formation of the cohere…
With a conventional lens sharpness of the image is always limited by the wavelength of light. An unconventional alternative to a lens, a slab of negative refractive index material, has the power to focus all Fourier components of a 2D image, even those that do not propagate in a radiative manner. Such "superlenses" ca…
Impregnation of low-density polyethylene (LDPE) with styrene using supercritical (SC) CO 2 as the swelling agent was studied at 35 °C in a pressure range from 90 to 160 bar. The concentration of styrene in the fluid phase ranged from 0 to 1.668 mol/L. The soaking time varied from 4 to 36 h. In the presence of azobis(i…
Dilute blends of two guest monodisperse n -alkanes one, n -C 122 H 246, shorter and one, n -C 246 H 494, longer than the pure host, n -C 162 H 326, have been investigated regarding the kinetics and morphology of both spherulitic growth and cellulation to clarify the related phenomena in polymers. All samples were crys…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA Tris-hydroxymethyl-Substituted Derivative of Gd-TREN-Me-3,2-HOPO: An MRI Relaxation Agent with Improved EfficiencySharad Hajela, Mauro Botta, Sabrina Giraudo, Jide Xu, Kenneth N. Raymond, and Silvio AimeView Author Information Department of Chemistry, University of C…
A novel synthetic route to heterobifunctional poly(ethylene glycol) (PEG) derivatives containing both mercapto and acetal terminal groups was established in this study using anionic ring opening polymerization of ethylene oxide (EO) using potassium 3, 3-diethoxypropanolate (PDP) as the initiator, followed by the succe…
The structure of a single thread of Nephila edulis silk has been studied by in situ X-ray diffraction from a living spider. A systematic increase of orientational order with increasing silking speed up to 40 mm s-1 was observed. Within a few mm from the spinnerets exit, crystalline domains with a beta-poly(L-alanine)…
Readily available N-acylbenzotriazoles 2a-q efficiently acylate aqueous ammonia and primary and secondary amines to give primary, secondary, and tertiary amides in good to excellent yields. The wide applicability of the procedure is illustrated by the preparation of (i) alpha-hydroxyamides from alpha-hydroxy acids and…
We report the magnetotransport properties up to 7 T in the organic highly conducting Langmuir-Blodgett(LB) films formed by a molecular association of the electroactive donor molecule bis(ethylendioxy)tetrathiafulvalene (BEDO-TTF) and stearic acid CH$_3$(CH$_2$)$_{16}$COOH. We show the logarithmic decrease of dc conduc…