Materials Literature
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Surface second harmonic generation was used to obtain approximate orientational distributions of the side chains and the adsorbed liquid crystal (LC) molecules on a rubbed side-chain polyimide surface. Both the side chains and the LC molecules appear to be well aligned in the rubbing direction but tilted away from the…
${}^{139}\mathrm{La}$ rf enhancement experiments are shown to be an excellent tool for detecting changes of the local magnetic anisotropy in colossal magnetoresistance manganites. Based on this, we discuss the possibility of orbital ordering in ferromagnetic (FM) ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mat…
Abstract Six kinds of aromatic poly(amic acid) films, the precursor of polyimides, were uniaxially drawn by constant loads during thermal curing with varying the final curing temperature and the load. The in‐plane birefringence (Δn) generated by uniaxial orientation of polyimide molecules in the film plane was investi…
Smectic blue phases ( BP(Sm)) are thermotropic liquid crystalline phases which exhibit both three-dimensional orientational order, such as classical blue phases, and smectic positional order. BP(Sm) appear as the three-dimensional counterpart of twist grain boundary phases. X-ray scattering and optical polarizing micr…
We have investigated the local structure and photoluminescence properties of ultrasmall Ge islands grown on Si(111) covered with SiO2. Scanning electron microscopy and transmission electron microscopy measurements show that the islands have a hemispherical shape, and depending on the growth temperature, can be either…
We have grown epitaxial (Ba0.5, Sr0.5)TiO3 (BST) thin films on Si with very thin yttria-stabilized zirconia (YSZ) buffer layer. The thin YSZ buffer layer affects the stress state of the epitaxial BST layer as well as the growth behavior of the BST layer, i.e., the degree of epitaxy. The epitaxial BST films grown on Si…
The excitonic properties of high-quality ZnO/Zn0.88Mg0.12O multiquantum wells grown by laser-molecular-beam epitaxy were investigated using temperature-dependent optical absorption spectra from 5 K to room temperature. The strength of exciton-longitudinal-optical (LO) -phonon coupling was deduced from the temperature…
Inelastic neutron scattering was used to study the temperature (T) dependence of the lattice excitations in La 0.7Ca 0.3MnO (3). An optical Jahn-Teller phonon exhibits continuous but anomalous damping with increasing temperature in the ferromagnetic-metallic phase and collapses above the Curie temperature T(C) (240 K)…
The contribution of the itinerant states to the magnetocrystalline anisotropy (MA) energy of ${\mathrm{YCo}}_{5}$ and isostructural compounds has been calculated using a fully relativistic optimized LCAO band-structure scheme within the framework of density-functional theory in local spin density approximation (LSDA),…
The structural and physical properties of pseudocubic thin-film BaTi1−xFexO3(0.5⩽x⩽0.75) grown by pulsed-laser deposition are reported. This material is of interest because the corresponding bulk compounds have hexagonal structure for comparable x, and because the films are both ferroelectric and ferrimagnetic well ab…
Coupled magnetic–mechanical–electric effects in a composite with ferromagnetic rare-earth–iron alloys (e.g., Tb1−xDyxFe2) filled in ferroelectric polymers [e.g, poly(vinylidene-fluoride–trifluoroethylene) copolymer] are studied by using the Green’s function technique. Numerical results suggest a possible giant linear…
Devising ultrathin barrier layers to prevent Cu diffusion into SiO2-based dielectrics is a major challenge that must be met to increase the speed, number density, and performance of microelectronics devices. Here, we demonstrate the use of near-zero-thickness (<2-nm-thick) self-assembled molecular monolayers (S…
Bond contraction in the surface layers induces a compressive stress on the inner part of a grain and results in a size effect for ferroelectric materials in the nanometer size range. By using the Landau-Ginsburg-Devonshire free energy approach, the phase transitions and intrinsic ferroelectric properties of the lead z…
We investigate the highly frustrated spin and orbital superexchange interactions in cubic vanadates. The fluctuations of t(2g) orbitals trigger a novel mechanism of ferromagnetic interactions between spins S = 1 of V3+ ions along one of the cubic directions which operates already in the absence of Hund's rule exchange…
The piezoelectric properties of (1−x) Pb(Mg1/3Nb2/3)O3–xPbTiO3 (x=0.3–0.35), ceramics with a high degree of 〈001〉 fiber texture were investigated for possible actuator applications. Piezoelectric coefficients (d33) in excess of 1200 pC/N associated with strain levels up to >0.3% were observed in samples prepare…
The Peierls distortions in a two-dimensional electron-lattice system described by a Su-Schrieffer-Heeger type model extended to two-dimensions are numerically studied for a square lattice. The electronic band is just half-filled and the nesting vector is ($π/a$, $π/a$) with $a$ the lattice constant. In contrast to the…
The charge-density-wave transition in $\mathrm{TiSe}{}_{2}$, which results in a commensurate $(2\ifmmode\times\else\texttimes\fi{}2\ifmmode\times\else\texttimes\fi{}2)$ superlattice at temperatures below $\ensuremath{\sim}200\mathrm{K}$, presumably involves softening of a zone-boundary phonon mode. For the first time,…
We investigate theoretically the switching characteristics of semiconducting carbon nanotubes connected to gold electrodes under an external (gate) electric field. We find that the external introduction of holes is necessary to account for the experimental observations. We identify metal-induced gap states (MIGS) at t…
We calculate the interaction between two spherical colloidal particles embedded in the isotropic phase of a nematogenic liquid. The surface of the particles induces wetting nematic coronas that mediate an elastic interaction. In the weak wetting regime, we obtain exact results for the interaction energy and the textur…
Waves propagate through disordered systems in a variety of regimes. There is a threshold of disorder beyond which waves become localized and transport becomes restricted. The intensity I of the wave transmitted through a system has a dependence on the length L of the sample that is characteristic of the regime. For ex…