Materials Literature
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Piezoelectric force microscopy is employed to study the ferroelectric domain structure in a 600nm thick epitaxial BiFeO3 film. In the as-grown film, a mosaic-like domain structure is observed. Scans taken with the cantilever pointing along the principal crystallographic directions enabled us to reconstruct the polariz…
We characterize three nonstandard electrohydrodynamic instabilities in nematic liquid crystals composed of bent-core molecules. In addition to their shape, another important attribute of this material is that the anisotropy in the electrical conductivity changes sign as the frequency of the applied electric field chan…
Great improvement in the output power density of diamond FETs on a diamond homoepitaxial layer grown using a high-purity source gas is reported. For a device with a gate length of 0.1 µm and gate width of 100 µm, at 1 GHz, maximum output power density of 2.1 W/mm, maximum power gain of 10.9 dB, and power added efficie…
Abstract This paper describes the classification of magnetic point and space groups which are also referred to as antisymmetry groups or black-and-white groups . These groups play an important role in the description of discrete point sets in which the points are not only characterized by their spatial coordinates but…
We predict theoretically that the effective in-plane thermal conductivity of polar, amorphous thin films can be increased by surface phonon-polaritons significantly beyond their intrinsic bulk values. We show that the thermal conductivity due to surface phonon-polaritons increases with decreasing film thickness. In pa…
The dielectric spectra of CaCu3Ti4O12 is characterized by a large permittivity (εr>10000) with only a weak dependence on temperature over the temperature range 200–400 K. In this work, doping with 0.1–1.0 wt % ZrO2 has been shown to dramatically reduce the dielectric loss. At 0.5 wt % ZrO2,tanδ remains below 0.…
A Laser-stimulated synthesis of large silver nanoaggregates consisting of hundreds to thousands of nanoparticles is investigated. It is shown that the morphology of the synthesized nanostructures can be controlled with light and monitored via the evolution of the colloid absorption spectra. A solution method is demons…
The characterization of Pt/TiO2 (Degussa P25) catalyst system using atomic resolution Z-contrast images and electron energy loss spectroscopy in the scanning transmission electron microscope has recently revealed that Pt particles have a strong tendency to nucleate on the rutile phase of TiO2 rather than anatase. Comp…
This paper examines the response of electrolyte-saturated polymer gels, embedded with charged spherical inclusions, to a weak gradient of electrolyte concentration. These composites present a model system to study microscale electrokinetic transport processes, and a rigorous theoretical prediction of the bulk properti…
The sponge skeleton of the spine of sea urchins is found to be generated from nanocrystals 20–50 nm in size (main image). The nanocrystals make up the oriented architectures of various living species (see insets) in association with biopolymers; together they are in the form of inorganic–organic nanocomposites. This n…
We investigate the spin-Hall effect in a two-dimensional heavy-hole system with Rashba spin-orbit coupling using a nonequilibrium Green's function approach. Both the short- and long-range disorder scatterings are considered in the self-consistent Born approximation. We find that, in the case of long-range collisions,…
Results of structural neutron diffraction study, magnetization, and electron spin resonance (ESR) measurements are presented for insulating ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Ba}}_{x}{\mathrm{MnO}}_{3}(x=0.25)$ with the Curie temperature ${T}_{C}\ensuremath{\approx}129\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Det…
Using first-principles density functional calculations, we study the possible phases of CeMnNi$_{4}$ and show that the ground state is ferromagnetic. We observed the hexagonal phase to be lowest in energy whereas experimentally observed cubic phase lies slightly higher in energy. We optimized the structure in both pha…
The permeability of certain polymer membranes with impenetrable nanoinclusions increases with the particle volume fraction (Merkel et al., Science, 296, 2002). This intriguing observation contradicts even qualitative expectations based on Maxwell's classical theory of conduction/diffusion in composites with homogeneou…
Thermoelectric properties of a nanocontact made of two capped single wall nanotubes (SWNT) are calculated within the tight-binding approximation and Green's function method. It is found that semiconducting nanotubes can have high Seebeck coefficient very near the actual Fermi energy. This in turn leads to very high fi…
The amorphous conducting carbon films have been prepared at three different preparation temperatures with different boron-doping levels. The structural and transport properties of the same have been studied. X-ray diffraction measurements show that the 'd' value of the carbon depends both on atomic percentage of B in…
Magnetic and electric properties of a single crystal of ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{CoO}}_{3}$ have been experimentally studied. The system attains a ferromagnetic spontaneous moment below 170 K and exhibits a reentrant spin-glass phase below 100 K. In the ordered and the reentrant phases, the low-…
Boron doped amorphous conducting carbon films show MI transition induced by doping. In this paper we discuss the ac conductivity of the films, which lie on the insulating side of MI transition. The ac conductivity data is analyzed as a function of frequency as well as temperature for both real as well as imaginary par…
We present the results of Monte Carlo simulations of the magnetic properties of a model for a single nanoparticle consisting in a ferromagnetic core surrounded by an antiferromagnetic shell. The simulations of hysteresis loops after cooling in a magnetic field display exchange bias effects. In order to understand the…
The spin polarization of ferromagnetic alkali-metal iron antimonides KFe4Sb12 and NaFe4Sb12 is studied by point-contact Andreev reflection using superconducting Nb and Pb tips. From these measurements an intrinsic transport spin polarization Pt of 67% and 60% for the K and Na compound, respectively, is inferred which…