Materials Literature
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Application of rigorous integral method for computing the efficiency of arbitrary profile relief gratings used in all the optical spectral range is presented in this paper. The main progress of the method and the programs lays in numerical solution algorithm. In particular, an approximation of Green-function and its n…
Using path-integral Monte Carol simulations and an ab initio effective Hamiltonian, we study the effects of quantum fluctuations on structural phase transitions in the cubic perovskite compounds SrTiO3 and BaTiO3. We find quantum fluctuations affect ferroelectric (FE) transitions more strongly than antiferrodistortive…
Copper zinc ferrites ( Cu 1−x Zn x Fe 2 O 4 ) with x = 0.1, 0.2, 0.3 were prepared by solid state reaction technique. The samples were presintered at 900°C for 40 to 45 hrs and finally at 950°C for 4 hrs followed by air quenching. The lattice parameter, X-ray densities (D m ), grain size, bulk densities (D) and porosi…
Abstract An efficient combination of electrospray mass spectrometry (ES‐MS), spectrophotometric and 1 H‐NMR titrations in solution is used to characterize the assembly of the segmental ligand 2‐{6‐[1‐(3,5‐dimethoxybenzyl)‐1 H ‐benzimidazol‐2‐yl]pyridin‐2‐yl}‐1, 1′‐dimethyl‐5,5′‐methylene‐2′‐(5‐methylpyridin‐2‐yl)bis[1…
The interstitial oxygen centers in silicon and germanium are reconsidered and compared in an analysis based on the first-principles total-energy determination of the potential-energy surface of the centers, and a calculation of their respective low energy excitations and infrared absorption spectra. The total-energy c…
Abstract Recent developments in research on polyimides for high temperature applications have led to the synthesis of many new polymers. Among the criteria that determines their thermal oxidative stability, isothermal aging is one of the most important. Isothermal aging studies require that many experimental factors a…
We study the Jahn-Teller effect of positive fullerene ions $^2$C$_{60}^{+}$ and $^1$C$_{60}^{2+}$. The aim is to discover if this case, in analogy with the negative ion, possesses a Berry phase or not, and what are the consequences on dynamical Jahn-Teller quantization. Working in the linear and spherical approximatio…
Highly conductive ruthenium oxide (RuO2) has been epitaxially grown on LaAlO3 substrates by pulsed laser deposition. The RuO2 film is (h00) oriented normal to the substrate surface. The heteroepitaxial growth of RuO2 on LaAlO3 is demonstrated by the strong in-plane orientation of thin films with respect to the major a…
We report on the first measurements of the angle resolved energy distribution of correlated electrons created in single scattering events by low energy ( ${E}_{p}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}14$--25 eV) electrons. We combined coincidence and time-of-flight techniques to measure simultaneously ene…
This Letter addresses basic questions concerning ferroelectric order in positionally disordered dipolar materials. Three models distinguished by dipole vectors that have one, two, or three components are studied by computer simulation. Randomly frozen and dynamically disordered media are considered. It is shown that f…
We have performed transport and $^{13}C$ NMR measurements on the sulfur-based Bechgaard salt, (TMTTF${)}_{2}$Br, at different pressures. At low pressures the ground state antiferromagnetism is commensurate with the lattice, while at high pressures many signatures of incommensurate density waves are found. Evidence tha…
Micro-Raman spectroscopy and x-ray diffraction measurements have been used to identify the presence of hexagonal diamond polytypes in chemical vapor deposited diamond films. The presence of additional reflections, in addition to the normal cubic diamond reflections in the diffraction spectra and bands at 1306 and 1193…
Record values of colossal magnetoresistance (CMR) have been achieved in the antiferromagnetic phase of the La1−xCaxMnO3 system. At 125 K, the CMR of the La0.5Ca0.5MnO3 reaches nearly 1 000 000%. It increases exponentially to 100 000 000% at 57 K. While the ground state is primarily an antiferromagnet, application of a…
Rayleigh-Brillouin light-scattering spectroscopy performed on oriented samples of tetragonal SrTi${\mathrm{O}}_{3}$ reveals the presence of a new doublet at low temperatures. This scattering, also seen in KTa${\mathrm{O}}_{3}$, appears in addition to the broad central peak already reported by Lyons and Fleury. The lik…
Using electron paramagnetic resonance (EPR), we show the alignment of defect dipoles along the direction of the spontaneous polarization in polycrystalline BaTiO3 ceramics by subjecting the capacitors to a dc bias at elevated temperatures. The alignment is demonstrated to occur via orientation dependent EPR signals in…
A method is presented to obtain {\it ab initio} upper and lower bounds to surface energies of stress-driven discommensurate surface structures, possibly non-periodic or exhibiting very large unit cells. The instability of the stressed, commensurate parent of the discommensurate structure sets an upper bound to its sur…
We develop a molecular model of non-uniform deformations within the framework of liquid crystal rubber elasticity. We show that, similarly to the uniform case, the theory is not sensitive to the molecular details of polymer liquid crystal involved and the resulting elastic free energy is quite universal. The result of…
A method is presented for evaluating the dislocation mobility from measurements of the amplitudedependent internal friction in a vibrating solid. The formulation is based on an idea that the forward and backward motion of dislocations occurs during each period of a steady-state vibration, which is impeded by friction…
Manganese-zinc ferrite Mn1−xZnxFe2O4 with different values of x is prepared by the usual ceramic technique. X-ray analysis shows that the samples are cubic spinels (single phase). The lattice parameter, the theoretical density, the bulk density, and the porosity are deduced and their variation with Zn2+ additions is s…
The retention and imprint properties of ferroelectric Pb(Zr0. 53Ti0. 47)O3 (PZT) and SrBi2Ta2O9 (SBT) thin films are studied. A simple characterization technique which consists of four measurement pulses is used to differentiate the retention and imprint effects. The high concentration of oxygen vacancies in PZT capac…