Materials Literature
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We have studied the magnetic properties of (GaMnAs)m/(GaAs)n superlattices with magnetic GaMnAs layers of thickness between 8 and 16 molecular layers (ML) (23-45 Å), and with nonmagnetic GaAs spacers from 4 ML to 10 ML (11-28 Å). While previous reports state that GaMnAs layers thinner than 50 Åare paramagnetic in the…
Crackling noise is observed in many disordered non-equilibrium systems in response to slowly changing external conditions. Examples range from Barkhausen noise in magnets to acoustic emission in martensites to earthquakes. Using the non-equilibrium random field Ising model, we derive universal scaling predictions for…
We studied the influence of sample preparation and defects in the superconducting properties samples using atomic ratios of Mg:B=1:1 and Mg:B=1:2. Samples were characterized by SEM, and XRD, and the magnetization properties were examined in a SQUID magnetometer. The presence of Mg vacancies was determined by Rietveld…
The effects of structure and morphology on lithium storage in single-wall carbon nanotube (SWNT) bundles were studied by electrochemistry and nuclear magnetic resonance techniques. SWNTs were chemically etched to variable lengths and were intercalated with Li. The reversible Li storage capacity increased from LiC(6) i…
The glass transition temperature (Tg) in water is still uncertain, with conflicting values reported in the literature. As with other hyperquenched glasses, water exhibits a large relaxation exotherm on reheating at the normal rate of 10 kelvin (K) per minute. This release of heat indicates the transformation of a high…
Reduction of an oxide in hydrogen is a method frequently employed in the preparation of active catalysts and electronic devices. Synchrotron-based time-resolved X-ray diffraction (XRD), X-ray absorption fine structure (NEXAFS/EXAFS), photoemission, and first-principles density-functional (DF) slab calculations were us…
Recent research in several groups has identified a new class of metal colloidal nanoparticles that is able to enhance the efficiencies of surface-enhanced Raman scattering (SERS) by as much as 10 14 −10 15 fold. This enormous enhancement allows single-molecule detection and spectroscopy at room temperature. Previous s…
Introduction A key feature of the chemistry of layered materials is the location of molecules (guests) of interest within the relatively constrained region of the interlayer. As such, the incorporation of guest molecules into layered hosts affords a versatile approach towards obtaining novel nanocomposite materials. O…
Abstract Isotactic polypropylene hollow fibers were produced by melt spinning. Spinning speeds up to 1880 m/min were used, and sample hollowness (percentage void in cross section) ranged from 0 to 69%. The fiber samples were characterized using dynamic mechanical analysis, birefringence, tensile testing, and different…
Abstract Polyimide hybrid films containing bimetalic compounds were obtained by codoping poly(amic acid) with a barium and titanium precursor prepared from BaCO 3 , Ti(OBu) 4 , and lactic acid followed by casting and thermal curing. FTIR, WAXD, and XPS measurements showed that barium and titanium precursor could be tr…
The diffusivity, permeability, and solubility coefficients of O 2, N 2, CO 2, and CH 4 have been measured in PVC and in four samples of PVC functionalized with mercapto pyridine groups up to 6.8, 11, 21, and 46 mol %. It has been found that the permeability of all four gases progressively increases by a factor of more…
ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTPhotochromic Dendrimers Containing Six AzobenzenesLi-Xin Liao, Denise M. Junge, and Dominic V. McGrathView Author Information Departments of Chemistry, University of Arizona, Tucson, Arizona 85721, and University of Connecticut, Storrs,…
We describe a model in which ${f(T)=M(T)/M}_{\mathrm{max}}$ represents both the fraction of the itinerant electron density in the double-exchange (DE) theory and the magnetization \ensuremath{\sigma} in the current carrier density collapse (CCDC) theory. With this model, we have checked the DE and CCDC theories with o…
We present a scheme to identify quasicrystals based on powder diffraction data and to provide a standardized indexing. We apply our scheme to a large catalog of powder diffraction patterns, including natural minerals, to look for new quasicrystals. Based on our tests, we have found promising candidates worthy of furth…
Good quality extended x-ray absorption fine structure (EXAFS) spectra near the Ga K edge have been collected in wide pressure and temperature ranges (namely 0--16 GPa, 298--498 K) using the dispersive setup installed at the LURE synchrotron radiation facility and diamond anvil cell as pressure device. Energy dispersiv…
We study x-ray absorption spectra below the O $1s$ threshold in Sc-doped stoichiometric strontium titanate $({\mathrm{SrTiO}}_{3}).$ We find hole states at the top of the valence band and acceptor-induced levels just above the Fermi level. The x-ray absorption spectra features and their temperature dependence are in g…
The cosubstituted solid solution In 2 - 2 x Sn x Zn x O 3 - δ was acceptor-doped with Zn 2+ to form In 2 - x - y Sn x Zn y O 3 - δ ( y > x ). A 4% Zn 2+ “excess” can be introduced in In 1.6 Sn 0.2 Zn 0.2 O 3 - δ while maintaining the bixbyite structure. The n-type conductivity of the doped material decreases with zinc…
The electrical conductivity, Hall effect, and thermoelectric coefficient of Zn/Sn-cosubstituted In 2 O 3 (In 2 - 2 x Sn x Zn x O 3 - δ ), undoped In 2 O 3, and indium−tin oxide (ITO) were studied vs cation composition, state of reduction, and measurement temperature (over the range of 4.2−340 K). Carrier contents and…
We report on magnetic susceptibility, magnetization, electric resistivity, and ESR experiments on single crystals of the covalent-chain antiferromagnetic compounds $\mathrm{TlFe}{X}_{2}$ $(X=\mathrm{S},$ Se). Collinear magnetic order with strongly reduced moments sets in at ${T}_{\mathrm{N}}=196 \mathrm{K}$ for ${\mat…
The molecular models of tubular aluminumsilicate, imogolite, and tubular gibbsite for the comparison with imogolite were investigated by means of molecular dynamics simulations. The stability of these two models was tested in terms of the tube radii. It was shown that the total energy of tubular gibbsite is decreasing…