Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
FeSe thin films were prepared on GaAs(100) substrate by the selenization of Fe films using molecular-beam epitaxy. FeSe compound thin films were obtained at a substrate temperature above 380 °C. From the depth profiles of Fe and Se in the selenized film measured by Auger electron spectroscopy, it was confirmed that an…
Ferromagnet-insulator-ferromagnet tunnel junctions with one NiMnSb electrode were studied to test the 100% conduction electron spin polarization predicted from band structure calculations performed on this compound. This phenomenon, known as half-metallic ferromagnetism (HMF), should result in significantly larger jun…
CrO 2 films were deposited on Al2O3 and TiO2 by high-pressure decomposition of CrO3. They are metallic, with a residual resistivity ρ0 in the range 0.2–10 μΩ m. The resistivity below Tc varies as ρ0+αT2+βT7/2 as expected for a correlated fully spin-polarized d band. At Tc the resistivity changes slope but the sign rem…
Evidence for variable range hopping (VRH) is presented in resistivity measurements in thin films and bulk samples of different substituted x=0.3 manganese perovskites. The necessity to modify the Mott VRH model is shown and we have developed a model based on magnetic localization hopping, which is used to reproduce te…
Spherical, monodisperse, submicrometer-sized particles in the CoxNi(100−x) system have been synthesized by the polyol process over the whole chemical composition range. These fine particles have been insulated by a chemical treatment in solution by a superficial layer of MnO2. The microwave permeability of these passi…
We report an ab initio calculation of the binding energies and the nature of the excitonic states in the near-gap absorption spectrum of a real solid, ${\mathrm{Li}}_{2}$O. We calculate the ground-state properties using density-functional theory together with soft pseudopotentials. Applying Hedin's GW approximation fo…
Structural changes of tussah (Antheraea pernyi) silk fibroin films induced by heat treatment were studied as a function of the treatment temperature in the range 200–250°C. The DSC curve of tussah films with α-helix molecular conformation displayed characteristic endo and exo peaks at 216 and 226°C, respectively. Thes…
The effect of Fe doping (<20%) on the Mn site in the ferromagnetic (x=0.37) and the antiferromagnetic (x=0.53) phases of La1−xCaxMnO3 has been studied. Upon doping, no appreciable structure changes have been found in either series. However, conduction and ferromagnetism have been consistently suppressed by Fe d…
A probable heterodiamond ${\mathrm{BC}}_{2}$N structure that can be obtained from compression of graphitic ${\mathrm{BC}}_{2}$N at low temperature is proposed using first-principles calculations. The structure consists of a rhombohedral atomic arrangement and has a large bulk modulus comparable to that of diamond as w…
Permanent magnets play a vital role in modern society as a component in a wide range of devices utilized by many industries and consumers. In 1995, the world production of permanent magnets was estimated to be valued at $3.6 billion and growing at an annual rate of 12%. Bonded permanent magnets are the fastest growing…
Within the framework of a partial-density approach, the confinement of vibrations in spherical Si nanocrystals is studied and the Raman frequency shifts of Si spheres with different sizes are derived based on the Raman spectra obtained by a bond-polarizability model. The results obtained by the bond-polarizability mod…
The attributes of electron field emission from disordered matrix arrays of carbon nanotubes are studied and found to be quite reproducible in spite of the disorder, density, and quality variations from sample to sample. At low applied electric fields, the electron field emission current-voltage characteristics qualita…
In the substitutionally disordered narrow-gap semiconductor Pb_{1-x}Ge_xTe, a finite-temperature cubic-rhombohedral transition appears above a critical concentration $x \approx 0.005$. As a first step towards a first-principles investigation of this transition in the disordered system, a (hypothetical) ordered cubic P…
We apply ab initio quantum chemical methods to calculate correlation effects on cohesive properties of NiO, thereby extending a recently proposed scheme to transition-metal oxides with partially filled d bands. We obtain good agreement with experiment for the cohesive energy and show that the deviation of the lattice…
The bare and hydrogen-covered diamond (100) surfaces were investigated through pseudopotential density-functional calculations within the local-density approximation. Different hydrogen coverages, ranging from one to two, were considered. These corresponded to different structures (1\ifmmode\times\else\texttimes\fi{}1…
A “colossal” negative magnetoresistance (CMR) occurs in manganites at a first-order ferromagnetic transition. The Mn4+ and high-spin Mn3+ ions each contain localized t3 configurations; the t3–pπ–t3 superexchange interactions are antiferromagnetic. The orbital degeneracy of localized Mn3+:t3e1, Eg5 configurations is li…
The exciton-phonon coupling strength of PbS nanocrystals that strongly confine both charge carriers is investigated using resonant Raman scattering. The strength of this coupling (Huang-Rhys parameter S\ensuremath{\sim}0.7) is four orders of magnitude greater than that predicted theoretically for the intrinsic states…
Anomalous magnetic properties of organic coated NiFe2O4 nanoparticles have been reported previously (Berkowitz et al.).5 These properties included low magnetization with a large differential susceptibility at high fields and shifted hysteresis loops after field cooling, while Mössbauer spectra indicated that all of th…
The oxidation of liquid-gallium surfaces has been investigated with surface x-ray scattering techniques. By exposing the liquid-metal surface at room temperature to doses on the order of 180 L of oxygen where 1 L=${10}^{\mathrm{\ensuremath{-}}6}$ Torr s, a gallium oxide film with a well-defined thickness of \ensuremat…
The changes in density, wave functions, and self-consistent potentials of solids, in response to small atomic displacements or infinitesimal homogeneous electric fields, are considered in the framework of the density-functional theory. A variational principle for second-order derivatives of the energy provides a basis…