Materials Literature
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Nd-Fe-B permanent magnets prepared by rapid solidification have been extensively characterized by transmission electron microscopy at all stages of their development. Grains in the as-spun ribbons range in size up to several micrometers in their largest dimension. Excess Nd is trapped within some of the larger grains…
Magnetic susceptibility measurements of high purity MgO single crystals (<50-wt. ppm transition metals) by means of a vibrating-sample magnetometer shows an anomaly at 800 K. At the same temperature the electric conductivity increases anomalously, the static dielectric constant epsilon increases from 9 to approximatel…
Magnetization, magnetic susceptibility, and crystal structure are investigated on the ternary chromium arsenides CrM′As (M′=Ru,Rh,Pd) and ternary manganese phosphides and arsenides MnM′P(M′=Rh,Pd) and MnM′As(M′=Ru,Pd). MnRhP, MnRuAs, and MnPdAs are ferromagnets with a Curie temperature of Tc=401, 496, and 210 K, respe…
Anisotropic Nd-Fe-B magnets are produced from melt-spun ribbons by hot working technique. The processing is facilitated by improved workability. In order to obtain a sound magnet, it is important to suppress the crack initiation and growth. An investigation was carried out to study the deformation mechanism of the all…
We have succeeded in forming single-phase MnBi in its two ferromagnetic phases, the low-temperature phase (LTP) and the quenched high-temperature phase (QHTP). The formation process involves rapid solidification into the amorphous state followed by thermal annealing. The crystallization of the amorphous material invol…
Experimental results concerning the reduction of the amplitude nonuniformity of a Metglas 2605SC magnetostrictive delay line (MDL) after stress relief and current annealing under stress are reported. Nonuniformity is defined here as the fluctuation of the peak voltage V0 received by a coil around the MDL at a fixed po…
The influences of varying cerium, neodymium, cobalt, and silicon concentrations on the magnetic properties of Ce-Fe-B type magnets were investigated. The results indicated that magnets containing 13.5 at.% of cerium exhibits superior magnetic properties to those exhibited by magnets with higher rare-earth element comp…
From magnetization (M) and magnetostriction (λ) measurements as a function of magnetic field and stress, the temperatures of anisotropy compensation, Tm, for technologically important TbxDy1−x(Fe1−yTy)1.9 [T=Co,Mn (0.3≤x≤0.5) (0≤y≤0.3)] were determined. Measurements of M and λ encompassing Tm were made under compressi…
Using frequency-dependent dielectric susceptibility, we have studied three different types of relaxation phenomena, namely primary (\ensuremath{\alpha}), secondary (\ensuremath{\beta}), and conductivity (c) relaxation, in a sample of 25 vol % benzyl chloride in toluene. The measurement covers ten decades of frequency:…
Neutron diffraction, in conjuction with substitution of deuterium (D) for hydrogen (H), has been used to determine the structure of interlayer water in sodium- and nickel-substituted vermiculites. We have measured the intensities of the (00l) Bragg reflections as a function of relative humidity and H/D content, up to…
The electronic structure of the two-dimensional Penrose lattice is studied by numerical diagonalization of a tight-binding Hamiltonian for finite systems with up to 3571 sites. We have analyzed the smoothness of the energy spectrum and localization behavior of the wave functions by level statistics and a generalized p…
We report a full-band-structure calculation of frequency-dependent second-harmonic generation in odd-period strained [(Si${)}_{\mathit{n}}$/(Ge${)}_{\mathit{n}}$]/Si (001) superlattices for n=1, 3, and 5. We derive sum rules to show that for materials with filled valence bands and empty conduction bands, independent o…
The oxidation rate of silicon small particles prepared by a gas-evaporation method and with diameters ranging from about 20 to 500 nm is investigated by high-resolution transmission electron microscopy. It is found that the oxidation rate of silicon small particles is less than the rate for wafers, and decreases with…
Preisach-type models are suggested for the description of strain hysteresis of magnetostrictive materials. It is pointed out that the strain hysteresis has some peculiar properties in comparison with magnetic hysteresis. These peculiarities of strain hysteresis are discussed in detail along with the identification pro…
A new class of diluted magnetic semiconductor (DMS) based on a III-V semiconductor is reviewed. The new DMS, (In,Mn)As, was made possible by low temperature molecular beam epitaxial growth. Magnetic measurements and x-ray diffraction showed homogeneous incorporation of Mn in the films under certain growth conditions,…
A series of interstitial ternary nitrides R2Fe17N3−δ has been prepared via a gas-solid reaction for R=Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Y. These nitrides have structures related to the Th2Zn17 or Th2Ni17 structures of the R2Fe17 parent compounds, but the unit cell volumes are 6%–7% greater, and the Curie…
We report on x-ray scattering studies of the nematic to smectic-A transition in 4-cyano-4'-octylbiphenyl under nonequilibrium shear-flow conditions. As the transition is approached, the interplay between the viscous frictional and the flow-induced-fluctuation forces on the nematic director leads to a series of regimes…
A detailed self-consistent field theory is used to calculate the properties of end-adsorbed polymer chains, or polymer ‘‘brushes,’’ in equilibrium with a blend of adsorbing B polymer and nonadsorbing A polymer. The brush properties depend on χab, Na/Nb and β, where χab is the Flory interaction parameter characterizing…
X-ray-absorption fine-structure (XAFS) measurements of lead from 10 K through and above the melting transition at 600 K have been carried out. A cumulant expansion analysis provides data on the first four moments of the radial distribution of the first shell, which are used to construct a consistent temperature-depend…
Potential n-type dopants in diamond are investigated via ab initio methods. The well-known distortions around the deep donor N are found to arise from the interaction of the N lone pair with a C dangling bond. P, Li, and Na are all shallow dopants, but their solubilities are muh too low for doping via in-diffusion. Li…