Materials Literature
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We discuss the infrared reflectivity measurement on a $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ single crystal between $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and room temperature. The nine predicted $ab$-plane $E$ phonon modes are fully and unambiguously determined. The frequencies of the four ${A}_{1}$ $c$-axis phon…
OsB_2 crystallizes in an orthorhombic structure (Pmmn) which contains alternate boron and osmium layers stacked along the c-axis. The boron layers consist of puckered hexagons as opposed to the flat graphite-like boron layers in MgB_2. OsB_2 is reported to become superconducting below 2.1 K. We report results of the d…
Thermodynamic, structural, and electronic properties of isolated copper and iron atoms as well as their complexes with oxygen vacancies in tetragonal lead titanate are investigated by means of first principles calculations. Both dopants exhibit a strong chemical driving force for the formation of ${M}_{\mathrm{Ti}}\en…
We calculate the spin-transfer torque in Fe/MgO/Fe tunnel junctions and compare the results to those for all-metallic junctions. We show that the spin-transfer torque is interfacial in the ferromagnetic layer to a greater degree than in all-metallic junctions. This result originates in the half metallic behavior of Fe…
The optical orientation of the exciton spin in an ensemble of self-organized cubic GaN/AlN quantum dots is studied by time-resolved photoluminescence. Under a polarized quasi-resonant excitation, the luminescence linear polarization exhibits no temporal decay, even at room temperature. This demonstrates the robustness…
In this work, we demonstrate that the interaction of electromagnetic waves with a microstructured material formed by metallic wires connected to a metallic surface can be described using homogenization methods provided an additional boundary condition is considered. The additional boundary condition is derived by taki…
The lineshape in an auto-oscillator with a large nonlinear frequency shift in the presence of thermal noise is calculated. Near the generation threshold, this lineshape becomes strongly non-Lorentzian, broadened, and asymmetric. A Lorentzian lineshape is recovered far below and far above threshold, which suggests that…
A new crosslinking system based on azide-functionalized random copolymers has been defined for the preparation of substrates with controllable surface interactions. The azido group is used for both thermal- and photo-crosslinking, which is found to be very efficient. Furthermore, the use of UV irradiation for crosslin…
Excitons are generally believed not to exist in metals because of strong screening by free carriers. Here we demonstrate that excitonic states can in fact be produced in metallic systems of a one-dimensional character. Using metallic single-walled carbon nanotubes as a model system, we show both experimentally and the…
Abstract A novel polyvinylpyrrolidone (PVP)‐directed crystallization route is successfully developed for the shape‐selective synthesis of ZnO particles with distinctive shapes, including monolayer, bilayer, and multilayer structures, gears, capped pots, hemispheres, and bowls, at temperatures as low as 32 °C. This rou…
First-principles studies identify a vacancy mechanism underlying the unusually high O solubility and nucleation of stable O-enriched nanoclusters in defect-containing Fe. Oxygen, confined as an interstitial, shows an exceptionally high affinity for vacancies, an effect enhanced by spin polarization. If vacancies preex…
The Fokker-Planck equation for the probability $f(r,t)$ to find a random walker at position $r$ at time $t$ is derived for the case that the the probability to make jumps depends nonlinearly on $f(r,t)$. The result is a generalized form of the classical Fokker-Planck equation where the effects of drift, due to a viola…
We develop a quantitatively predictive theory for impurity-band ferromagnetism in the low-doping regime of Ga1-xMnxAs. We compare it with measurements of a series of samples whose compositions span the transition from paramagnetic insulating to ferromagnetic conducting behavior. The theoretical Curie temperatures depe…
We study the three-dimensional structure formation when atoms are deposited onto a substrate with a decagonal quasicrystalline order. Molecular dynamics calculations show that the adsorbate layer consists of ordered nanoscale domains with orientations determined by the underlying substrate symmetry. Depending on the r…
We measure the temperature dependence of the Raman spectra of metallic and semiconducting nanotubes. We show that the different trend in metallic tubes is due to phonon re-normalization induced by the variation in electronic temperature, which is modeled including non-adiabatic contributions to account for the dynamic…
Consider a layer made of a m3m insulator crystal, with faces cut parallel to a symmetry plane. Then bond it onto a semi-infinite mm2 piezoelectric substrate. For a X- or Y -cut of the substrate, a Love wave can propagate in the resulting structure and the corresponding dispersion equation is derived analytically. It t…
Functionally Graded Materials are inhomogeneous elastic bodies whose properties vary continuously with space. Hence consider a half-space (x_2>0) occupied by a special Functionally Graded Material made of an hexagonal (6 mm) piezoelectric crystal for which the elastic stiffness c44, the piezoelectric constant e15, the…
Measurements of resistivities of dilute iron based alloys show strong deviations from Matthiessen's rule. These deviations can be explained by a model in which spin up and spin down electrons conduct in parallel. The results are consistent with the theory of impurity shielding in these alloys. [This 1967 paper provide…
Abstract Polyelectrolyte microcapsules are made by layer‐by‐layer (LbL) coating of a sacrificial template, followed by decomposition of the template, to produce hollow microcapsules. In this paper, we report on the in vivo cellular uptake, degradation and biocompatibility of polyelectrolyte microcapsules produced from…
In situ sol-gel polymerization is demonstrated for fabricating transparent poly(methyl methacrylate) (PMMA)-ZnO quantum dot (QD)- hybrid materials in bulk dimension. The transparent PMMA-ZnO QD hybrid materials exhibit enhanced UV-shielding effects in the entire UV range, even at concentrations as low as 0.02 wt %.