Materials Literature
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The crystal and magnetic structure of the hard magnetic alloy Mn1.074Al0.871C0.005, which has a body centered tetragonal structure, has been investigated. Neutron diffraction data shows that Mn0.992, C0.008 occupy the (0,0,0) site and Mn0.082, Al0.871, C0.047 occupy the ( 1/2 , 1/2 , 1/2 ) site. The magnetic moments o…
The effect of Zr on the hard magnetic properties of Sm(Co0.745−xFe0.200Cu0.055Zrx)7.5 permanent magnets has been examined by correlating the coercive field with the microstructure. Optical and transmission electron microscope studies show that Zr suppresses the precipitation of a SmCoCu phase and controls the size of…
A model is presented for the contribution of ground-state charge transfer between a metal and adsorbate to surface-enhanced Raman scattering (SERS). It is shown that this contribution can be understood using the vibronic theory for calculating Raman intensities. The enhancement is due to vibronic coupling of the molec…
The physical properties of vapor deposited amorphous solid water, (H2O)as, depend strongly on a parameter not investigated before: the state of the vapor prior to deposition on a cryoplate. Supersonic flow conditions give (H2O)as desposits with a very rugged surface, whereas breakup of supersonic flow by a baffle give…
A theoretical description of the static structural, vibrational, and solid-solid phase-transition properties of alkali halides is presented. The description is ab initio involving pseudopotentials and density-functional theory. Using NaCl as a prototypical example, we conclude that properties of alkali halides can be…
Raman spectra in superionic glasses ${(\mathrm{AgI})}_{x}{({\mathrm{Ag}}_{2}\mathrm{O}\ifmmode\cdot\else\textperiodcentered\fi{}n{\mathrm{B}}_{2}{\mathrm{O}}_{3})}_{1\ensuremath{-}x}$ for various values of $x$ ($0.1\ensuremath{\le}x\ensuremath{\le}0.55$) and for various $n (2\ensuremath{\le}n\ensuremath{\le}4)$ are re…
Growth of grains with sizes many times (>50×) larger than the film thickness and with uniform (111) texture, has been achieved in ultrathin (<100 nm) films of Si on SiO2. Growth of these secondary grains is driven by minimization of anisotropic surface energy. As a result, the secondary grain growth rate…
The temperature dependence of the x-ray structure factor has been measured for ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ and ${\mathrm{As}}_{x}{\mathrm{S}}_{1\ensuremath{-}x}$ glasses of compositions $x=0.40,0.33,0.19, \mathrm{and} 0.11$. In all of these glasses, a surprising increase in the first-diffraction-peak intens…
A new type of bolometer detector for the millimeter and submillimeter spectral range is described. The bolometer is constructed of silicon using integrated circuit fabrication techniques. Ion implantation is used to give controlled resistance vs temperature properties as well as extremely low 1/f noise contacts. The d…
Magnetic and crystallographic measurements have been carried out for Mn2−xMxSb (M=Ti, V, Cr, Fe, and Co) in order to study the nature of the transition from ferrimagnetic (Fr) to antiferromagnetic (AF) states. The magnetic phase diagrams have been determined. In the cases of M=Ti and Fe, only the Fr phase is observed.…
The electronic structure of carbon overlayers on Ni(111) has been investigated by using photoemission, energy-loss, and ionization-loss spectroscopy techniques. The combined use of these spectroscopies gives a detailed picture of these surfaces which have important catalytic implications. The carbidic carbon overlayer…
A model, based on the Sm-Co system between SmCo5 (1:5) and Sm2Co17 (2:17 R and 2:17 H), is proposed to describe the metallurgical behavior of Sm(Co,Fe,Cu,Zr)z alloys between 6.8<z<8.5 in the development of hard magnetic properties. The same phases are encountered in both the binary and multicomponent all…
We have calculated the electronic structure of PtMnSb in order to explain the very high magneto-optical Kerr effect (over 2.5° at 720 nm at room-temperature) of this compound. It is shown that this behavior is related to the unusual electronic properties of PtMnSb: it is a half-metallic ferromagnet like NiMnSb. The ex…
A mathematical theory of hysteresis in ferromagnetic materials is presented based on existing ideas of domain wall motion and domain rotation. Hysteresis is shown to occur as a result of impedances to changes of magnetization such as when domain walls are pinned, while the mutual interactions of the magnetic moments a…
Carbon films were prepared by ion-beam as well as rf-discharge deposition, and annealed at temperatures up to 950\ifmmode^\circ\else\textdegree\fi{}C. Raman spectra of these films, in the range 1000-1800 ${\mathrm{cm}}^{\ensuremath{-}1}$, were analyzed via a best fit to computer-generated line shapes, used to simulate…
We report the properties of a new class of high-performance permanent magnets prepared from Nd-Fe-B and Pr-Fe-B alloys. Magnetic hardening is achieved by rapid solidification. Energy products of these isotropic materials can exceed 14 MGOe with intrinsic coercivities of ∼15 kOe. X-ray and microstructural analyses indi…
A new compound composed of Nd, Fe, and a small quantity of B (about 1 wt. %) has been found, which has a tetragonal structure with lattice constants a=0.880 nm and c=1.221 nm. This phase, which has the approximate composition, 12 at. % Nd, 6 at. % B and balance Fe, possesses remarkable magnetic properties. From the ap…
Measurements of DC electrical conductivity and ESR were made on 35TeO 2 -(65-x)V 2 O 5 -xFe 2 O 3 (mol%) glasses. They suggest that when x is changed from 0 to 1, the conductivity increases due to a decrease in effective electron hopping distance between the transition metal ions. When x is increased to greater than u…
Abstract Extreme Farbtonunterschiede bei Perylen‐3,4:9,10‐bis(dicarboximid)‐Pigmenten lassen sich durch eine geometrische Betrachtungsweise der Ergebnisse von Kristallstrukturuntersuchungen deuten. Die bei den meisten N , N ′‐Dialkylperylen‐3,4:9,10‐bis(dicarboximiden) angetroffene parallele Anordnung benachbarter Mol…
Several water-soluble paramagnetic metalloporphyrins were found to increase significantly the relaxation rate (1/T1) of water. Such compounds are known to be selectively retained by tumors in animals, and consequently we identify them as potential contrast agents for tumors in NMR imaging.