Materials Literature
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Recent studies show that the magnetic properties of epitaxial thin films of magnetite (Fe3O4) deviate strongly from bulk behavior: it is difficult to saturate thin films, ultrathin films may become super paramagnetic, their saturation magnetization drops to zero, and the local magnetic moments are oriented out of plan…
We report both experimental measurements and molecular simulations of the melting and freezing behavior of simple fluids in porous media. The experimental studies are for carbon tetrachloride and nitrobenzene in controlled pore glass (CPG) and Vycor. Differential scanning calorimetry (DSC) was used to determine the me…
The improvement in oxygen barrier properties of poly(ethylene terephthalate) (PET) by incorporation of an impermeable phase such as crystallinity or talc platelets was examined. Crystallinity was induced by crystallization from the glassy state (cold crystallization). Microlayering was used to create talc-filled struc…
Through a systematic investigation of the complete dielectric tensor, between 0.5 and 5.0 eV, of Fe3O4 and of related spinel ferrites, i.e., MgFe2O4, Li0.5Fe2.5O4, NiFe2O4, and CoFe2O4, we have established that intervalence charge transfer and intersublattice charge transfer transitions dominate the optical and magnet…
The electronic structure of yttrium aluminum garnet $({\mathrm{Y}}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12})$ is studied by means of first-principles local-density calculations. Results on band structure, density of states, partial density of states, effective charges, bond order, charge-density distributions, equilibriu…
A new class of nanocrystalline alloys with composition Fe44Co44Zr7B4Cu1 has been developed. This and similar alloys of general composition (Fe, Co)–M–B–Cu (where M=Zr, Hf, Nb, etc.) have been named HITPERM. They offer large magnetic inductions and excellent soft magnetic properties at elevated temperatures. Thermomagn…
We have synthesized nine rodlike compounds of nanometric dimension with general formula [M(bpy) 3 -(ph) n -M‘(bpy) 3 ] 4+ (M = M‘ = Ru(II); M = M‘ = Os(II); M = Ru(II), M‘ = Os(II); bpy = 2,2‘-bipyridine; ph = 1,4-phenylene; n = 3, 5, 7; the central phenylene unit bears two alkyl chains for solubility reasons; the met…
We develop a mean-field theory of carrier-induced ferromagnetism in diluted magnetic semiconductors. Our approach represents an improvement over standard Ruderman-Kittel-Kesuya-Yosida model allowing spatial inhomogeneity of the system, free-carrier spin polarization, finite temperature, and free-carrier exchange and c…
Linear response methods applied to electron systems often display a level of accuracy which is notable when viewed in terms of the strengths of perturbing interactions. Neglect of higher response terms is in fact justifiable in many cases and it can be shown to stem from an intrinsic interference between atomic and el…
We show that electron-ion structure factors in fluid metallic systems can be well understood from an application of linear response in the electron system, combined with hard-sphere like correlation for the ionic component. In particular, we predict that electron-ion structure factors fall into two general classes, on…
We propose a novel ultrafast pulsed laser deposition (PLD) technique, which eliminates the well-known problem of contamination of the films produced by PLD with particulates ejected from the target. The method uses low energy, picosecond duration laser pulses delivered onto a target at rates of several tens of MHz and…
Density-functional theory (DFT) studies are performed to examine geometric and electronic properties of orthorhombic bulk ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$ as well as of its (010) oriented surface. Electronic states, total energies, as well as atom forces (used to obtain equilibrium geometries) are computed with the…
Research on the magnetocaloric effect and its application for cooling near room temperature over the past few years has helped to move this phenomenon from a scientific curiosity to an emerging technology. Two of the most important advances include the demonstration which proved that it is possible to obtain significa…
Highly sulfonated polyaniline prepared via a synthetic scheme using leucoemeralding base (LEB−SPAN) has been studied using X-ray photoelectron spectroscopy (XPS). A sulfonation level ( S / N ratio) as high as 0.80 ± 0.10 has been revealed in XPS analysis, agreeing well with the element chemical analysis results (∼0.78…
A magnetic sheet made of Fe–Si–Al flakes was found to have excellent permeability and electromagnetic-interferences characteristics in a quasimicrowave band. The flakes prepared by attrition were embedded in a polymer with their planes lying parallel to the sheet plane. This sheet exhibits a peculiar dual dispersion i…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTCyclodextrin-Modified Gold Nanospheres. Host−Guest Interactions at Work to Control Colloidal PropertiesJian Liu, Sandra Mendoza, Esteban Román, Matthew J. Lynn, Renliang Xu, and Angel E. KaiferView Author Information Center for Supramolecular Science, Department of Che…
Modified SERS (surface-enhanced Raman scattering) substrates are based on self-assembled monolayers (SAMs) formed from compounds such as alkanethiols. Chain lengths ranging from ethanethiol to octadecanethiol were used to investigate properties of modified SERS substrates. These properties include determining the magn…
We study photoinduced electron transfer from derivatives of poly(p-phenylenevinylene) (PPV) and nanocrystals of cadmium selenide via photoluminescence (PL) quenching and photoinduced absorption (PIA) spectroscopy. Using size-dependent quantum confinement to vary the energy levels of the nanocrystal acceptors, and chem…
A first-order transition above the Curie temperature for ferromagnetic La(FexSi1−x)13 (x=0.86 and 0.88) compounds has been confirmed by applying a magnetic field. The magnetic state changes from the paramagnetic to the ferromagnetic state and the transition field increases with temperature, indicating an itinerant ele…
We report experimental and theoretical investigations on the pressure dependence of the Raman-active radial and tangential vibrational modes of single-wall carbon-nanotube bundles. Using 514.5-nm excitation, we find that the radial mode intensity disappears beyond 1.5 GPa, and the tangential mode intensity also drops…