Materials Literature
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Metal organic framework-5 (MOF-5) was recently suggested to possess an exceptionally large negative thermal-expansion coefficient. Our direct experimental measurement of the thermal expansion of MOF-5 using neutron powder diffraction, in the temperature range of 4 to 600 K, shows that the linear thermal-expansion coef…
We present new simulation results for the specific heat in a classical model of a binary mixture glass-former in two dimensions. We show that in addition to the formerly observed specific heat peak there is a second peak at lower temperatures which was not observable in earlier simulations. This is a surprise, as most…
When an excess charge carrier is added to a one-dimensional (1D) semiconductor immersed in a polar solvent, the carrier can undergo self-localization into a large-radius adiabatic polaron. We explore the local optical absorption from the ground state of 1D polarons using a simplified theoretical model for small-diamet…
We develop the cluster self-consistent field method incorporating both electronic and lattice degrees of freedom to study the origin of ferromagnetism in Cs$_{2}$AgF$_{4}$. After self-consistently determining the harmonic and anharmonic Jahn-Teller distortions, we show that the anharmonic distortion stabilizes the sta…
We demonstrate voltage control of the magnetic anisotropy of a (Ga,Mn)As device bonded to a piezoelectric transducer. The application of a uniaxial strain leads to a large reorientation of the magnetic easy axis, which is detected by anisotropic magnetoresistance measurements. Calculations based on the mean-field kine…
A series of dimesitylboron (B)- or ditolylamino (N)-substituted ladder-type pentaphenylenes (PP) has been designed and synthesized. The UV-vis absorption spectra of compounds BPPN, BPPB, and NPPN reveal an identical maximum wavelength at 432 nm, which indicates that the B and N centers have very similar contributions…
We present an atomistic 3-D simulation study of the performance of graphene-nanoribbon (GNR) Schottky-barrier field-effect transistors (SBFETs) and transistors with doped reservoirs (MOSFETs) by means of the self-consistent solution of the Poisson and Schrodinger equations within the nonequilibrium Green's function (N…
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We have investigated the effect of partial isovalent anion substitution in Ga1-xMnxAs on electrical transport and ferromagnetism. Substitution of only 2.4% of As by P induces a metal-insulator transition at a constant Mn doping of x=0.046 while the replacement of 0.4% As with N results in the crossover from metal to i…
SrEr$_2$O$_4$ has been characterised by low-temperature powder neutron diffraction, as well as single crystal specific heat and magnetisation measurements. Magnetisation measurements show that the magnetic system is highly anisotropic at temperature above ordering. A magnetic field of 280 kOe applied at $T=1.6$ K does…
It is shown that a k=0, A_{2u} distortion of the terbium tetrahedral network in Tb2Ti2O7 accounts for the apparent isolation of single tetrahedra as seen in neutron scattering studies. Single tetrahedron collective spin states, rather than individual spins, account for the main features of the spin liquid state, namel…
Spin kinetics in $n$-type InAs quantum wells under intense terahertz laser fields is investigated by developing fully microscopic kinetic spin Bloch equations via the Floquet-Markov theory and the nonequilibrium Green's function approach, with all the relevant scattering, such as the electron-impurity, electron-phonon…
The spin-spiral (SS) type of magnetization is studied with the Hubbard model. Consideration of noncollinearity of the magnetic moments results in a phase diagram which consists of regions of the SS and paramagnetic states depending on the number of electrons and the parameter U/t (U is the Hubbard repulsion, and t is…
The capability to control the type and amount of charge carriers in a material and, in the extreme case, the transition from metal to insulator, is one of the key challenges of modern electronics. By employing angle-resolved photoemission spectroscopy we find that a reversible metal to insulator transition and a fine-…
The combined effects of hydroxyl/amino functional groups of aromatics and surface O-containing groups of carbon nanotubes on adsorption were evaluated. When normalized for hydrophobicity, 2,4-dichlorophenol and 2-naphthol exhibited a greater adsorptive affinity to carbon nanotubes and graphite (a model adsorbent witho…
This Account provides an overview of the methods that are currently being used to study the electromagnetics of silver and gold nanoparticles, with an emphasis on the determination of extinction and surface-enhanced Raman scattering (SERS) spectra. These methods have proven to be immensely useful in recent years for i…
Gold, enigmatically represented by the target-like design of its ancient alchemical symbol, has been considered a mystical material of great value for centuries. Nanoscale particles of gold now command a great deal of attention for biomedical applications. Depending on their size, shape, degree of aggregation, and loc…
The use of adjustable speed drives has introduced new electrical stresses in stator insulation systems. Many applications, in which the inverter and motor are placed at different locations, have led to further enhancement of these stresses and to unexpected failures within these motors. In this article, the main respo…
SmCo5 sintered magnets are produced according the following main processing: milling until single crystal particle size, compaction and sintering. It is necessary high density to maximize remanence, but small grain size to maximize coercivity. A sintering model able to incorporate both, the densification rate and the…
Boron carbide (B4C) and silicon carbide (SiC) are materials with high hardness and low density what make them very useful in various applications, such armor plates. Hot press sintering of B4C-SiC composites was studied. The powder mixture was obtained in situ by carbothermal reduction using B2O3, SiO2 and carbon blac…