Materials Literature
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Structural and dielectric evidences are advanced to show that the ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{TiO}}_{3}$ (SCT) system undergoes an antiferroelectric (AFE) phase transition in the composition range $0.18\ensuremath{\le}x\ensuremath{\le}0.40$. Stabilization of the AFE phase, instead of the…
The cyclic hexamer obtained by the condensation of furan and acetone can be used as a convenient starting material for the syntheses of calix[6]pyrrole 1 and of several “hybrid systems” containing both furan and pyrrole units. The solid-state structure of 1 shows a water molecule held inside the cavity by six hydrogen…
Efforts have been made to characterize the mechanical properties of carbon nanotubes. Previous work has concentrated on the tubes' longitudinal properties, and studies of their radial properties have lagged behind. We have used a scanning probe microscope with an indentation/scratch function to investigate the radial…
A model for the transport of nitrogen in austenitic stainless steel at temperatures around 400 °C is presented and discussed. The model considers the diffusion of nitrogen under the influence of trapping and detrapping at trap sites formed by local chromium. Nitrogen depth profiles simulated on the basis of the model…
The underlying physical phenomena behind the increased reflection/diffraction efficiency of holographically formed polymer-dispersed liquid crystal gratings formed from blended oligomers are investigated. Using parameters determined by in situ diffraction measurements during grating formation, a phenomenological diffu…
Optical conductivity data of the intermetallic compounds $({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{V}}_{x}{)}_{3}\mathrm{Al}$ ( $0\ensuremath{\le}x\ensuremath{\le}0.33$) reveal that their density of states around the Fermi energy ( ${E}_{F}$) is strongly reduced as $x$ is increased. In particular, ${\mathrm{Fe}}_{2}\…
The two-orbital model for manganites with both noncooperative and cooperative Jahn-Teller phonons is studied at hole density x = 0.5 using Monte Carlo techniques. The phase diagram is obtained by varying the electron-phonon coupling and the t(2g)-spins exchange. The insulating CE-type charge- and orbital-ordered state…
A thermodynamic theory is developed for dense laminar domain structures in epitaxial ferroelectric films. It is found that, at some critical misfit strain between the film and substrate, the 90 degrees c/a/c/a domain structure becomes unstable with respect to the appearance of the polarization component parallel to do…
We suceeded in the preparation of polycrystalline Ca_2FeReO_6 which has a Curie temperature of 540 K, the highest value of all magnetic perovskites investigated up to now. This material has been characterised by X-ray and neutron powder diffraction. We found at 548 K a monoclinic unit cell (space group P2_1/n) with a=…
The elaboration of solids from the molecular scale by a kinetically controlled methodology is one of the main challenges of molecular chemistry. In the long term, this should permit the design of solids with desired properties. Here, some examples are given which show a few methods that have been used for the preparat…
Monodisperse, rodlike molecules 1 composed of repeating individual chromophores that have substantial electronic interactions in the ground state have been synthesized by the meso – meso coupling of porphyrins. The 128-mer (n=63) at about 106 nm long is the longest such system known. The S1 states are delocalized over…
We report that calculating the Gibbs free energy of the alpha-Al2O3 (0001) surfaces in equilibrium with a realistic environment containing both oxygen and hydrogen species is essential for obtaining theoretical predictions consistent with experimental observations. Using density-functional theory we find that even und…
We construct the 1/S spin-wave expansion for double exchange ferromagnets at T=0. It is assumed that the value of Hund's rule coupling, J_H, is sufficiently large, resulting in a fully saturated, ferromagnetic half-metallic ground state. We evaluate corrections to the magnon dispersion law, and we also find that, in c…
Using Brownian molecular dynamics simulation, we study the surface dynamics near the reconstruction transition of W(100) via a model Hamiltonian. Results for the softening and broadening of the surface phonon spectrum near the transition are compared with previous calculations and with He atom scattering data. From th…
We have measured the 161 Dy Mössbauer effects on the cubic ferroquadrupolar ordering compound DyB 6 . In the antiferromagnetic phase, the Mössbauer spectra are interpreted well by a single set of hyperfine parameters which gives the Dy magnetic moment of 9.8 µ B . The nuclear quadrupole splitting implies that the crys…
Aliphatic polypyromellitimides having high crystallinity were synthesized by the high-pressure thermal polycondensation of the nylon-salt-type monomers XPME composed of aliphatic diamines and pyromellitic acid p-diethyl esters. The polymer-forming reactivity of the salt monomers XPME was comparable to that of the pare…
The microscopic a parameter, which alone is needed to describe the surface sensitive dependence of second-harmonic generation from jellium metals, is calculated within a time-dependent local-density-functional approximation for frequencies between zero and twice the bulk plasmon. The calculations incorporate an extrin…
New types of second-order nonlinear optical properties of hexagonal ${\mathrm{YMnO}}_{3}$ have been studied, caused by the coexistence of the noncentrosymmetric ferroelectric ordering of charges and the centrosymmetric spin ordering below its Neel temperature ${T}_{N}.$ Using time-dependent perturbation theory and the…
Compositionally modulated structures consisting of La2/3Ca1/3MnO3 ferromagnetic (FM) layers and La1/3Ca2/3MnO3 antiferromagnetic (AF) layers, with layer thickness 1.5 nm ⩽tFM,tAF⩽6 nm, were grown on (100)LaAlO3 by pulsed laser deposition. Thermomagnetic and isothermal magnetic measurements reveal an exchange-biasing m…
The surface shape and the spatial distribution of strain in GaInAs/InP multilayer gratings is experimentally determined by combining high-resolution x-ray diffraction and grazing-incidence diffraction. Dramatic deformations of the diffraction patterns in the measured reciprocal space maps of such gratings indicate a s…