Materials Literature
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Miniaturized triblock copolymers have been found to self-assemble into nanostructures that are highly regular in size and shape. Mushroom-shaped supramolecular structures of about 200 kilodaltons form by crystallization of the chemically identical blocks and self-organize into films containing 100 or more layers stack…
We use recent theoretical advances to develop a new functional form for interatomic forces in bulk silicon. The theoretical results underlying the model include a novel analysis of elastic properties for the diamond and graphitic structures and inversions of ab initio cohesive energy curves. The interaction model incl…
The shape of metallic constrictions of nanoscopic dimensions (necks) formed using a scanning tunneling microscope (STM) is shown to depend on the fabrication procedure. Submitting the neck to repeated plastic deformation cycles makes possible to obtain long necks or nanowires. Point-contact spectroscopy results show t…
Pd and Pt have been shown to be highly polarizable when mixed with ferromagnets like Ni, Fe, and Co. In these alloys the total moment, or magnetization cloud, is produced by the magnetic moment plus the induced moment on the surrounding atoms. With diffuse magnetic scattering of neutrons, it is possible to measure the…
We have developed an artificial preparation scheme to produce ferrite films in which magnetic and nonmagnetic layers were alternated at the atomic scale. Laser ablation deposition (LAD) was used to deposit layers of lithium ferrite and aluminum oxide to a thickness ranging between 2–3 Å each. In contrast to previous e…
Phosphorus doped polycrystalline diamond films were grown by hot-filament chemical vapor deposition using trimethyl phosphite as the doping source. Phosphorus incorporation into the diamond films was established using secondary ion mass spectroscopy. Current–voltage characteristics were measured and the resistivities…
The use of additives of corundum structure M{sub 2}O{sub 3} (M=Cr, Al) is an effective way of promoting grain growth of uranium dioxide. The high-temperature compressive deformation of large-grained UO{sub 2} doped with these oxides has been investigated and compared with that of pure UO{sub 2} with a standard microst…
Ferrimagnetic Nd6Fe14−xAlx compounds with x=3, 3.5, and 4 have been studied by magnetization measurements in fields up to 9 T. Néel temperatures were determined from Mössbauer spectra to be 308, 286, and 239 K, respectively. The net magnetization at T=4.2 K is 3.6 μB/f.u.(x=3), 2.2 μB/f.u.(x=3.5), and zero for x=4. Me…
In this work we have studied in detail the effect of MgO on magnetic properties and intergranular microstructure. We have found that both coercivity and thermal stability can be remarkably enhanced by the intergranular addition of MgO. For Nd22Fe71B7 magnets with 2 wt % MgO addition, the coercivity at room temperature…
Mossbauer effect studies (ME) for members of the alkylene-diammonium series, (CH2)n(NH3)2Fe(II)Cl4, where n=3, 4, 5, and 6 are presented. At 78 K the ME spectra reveal similar general features showing an 8 line well split hyperfine spectra; the effective magnetic field is in the range 18.5–20 T. Fitting the magnetizat…
Ceramic samples of composition (La1−xGdx)2/3Ca1/3MnO3 were prepared and used as targets to grow films onto LaAlO3 substrates by pulsed laser deposition. Comparison of the electrical resistance and thermopower, measured vs temperature and applied magnetic fields, indicates transport dominated by positively charged smal…
The cationic ring-opening polymerization of six-membered cyclic pseudoureas, 2-(1-pyrrolidinyl)- (2a) and 2-morpholino-5,6-dihydro-4H-1,3-oxazine (2b), was examined, which proceeded in two different ways, depending on the nature of initiator. The polymerization of 2 with methyl p-toluenesulfonate or trifluoromethanesu…
In this article the effects of dipolar and exchange interactions on the remanence ratio and coercivity in granular solids are examined using a generalized three-dimensional Monte Carlo model. This model allows the final configuration of magnetic moments to be calculated as a function of concentration, temperature and…
Using the interference of laser beams, we have fabricated the periodic arrays of submicron wires in Fe/C and Fe/Cr thin-film alloys. The array formation is found to arise from iron agglomeration in interference maxima. The dramatic decay of the in-plane magnetic anisotropy was observed in the fabricated arrays with de…
BaCoS 2 is a layered Mott–Hubbard insulator that orders antiferromagnetically near 300 K. We report magnetic susceptibility measurements on polycrystalline BaCoS2 from 77 to 800 K, and in- and out-of-plane measurements on single crystals from 2 to 350 K. We also report a powder neutron refinement of the magnetic struc…
Noise generated by a transformer core has been reduced by improving material and design, but further reduction is still required. To obtain the reduction, the comprehension of noise generating mechanism is important. It is achieved by detailed investigation of core vibration. A vibration measuring system utilizing a l…
This form of strontium germanium trioxide has the same structure as that reported by Hilmer [Sov. Phys. Crystallogr. (1963). 7(5), 573–576] except that it has monoclinic rather than hexagonal symmetry. Two forms of SrGeO3 are known at present: this monoclnic form and a triclinic form reported by Nadezhina, Pobedimskay…
The phase transformation and magnetic properties of nanocomposite (Nd0.95La0.05)9.5(Fe1−xCrx)81.5B9, where x=0, 0.033, 0.067, and 0.1, melt–spun ribbons have been studied. For Cr-free ribbons (i.e, x=0,) a slight substitution of La for Nd decreases the crystallization temperature of the over-quenched ribbons. Moreover…
The x-ray-photoemission spectra of the core levels and valence-band region of ${\mathrm{NiS}}_{2}$ is interpreted in terms of a cluster model in the impurity limit. The d-d and p-d charge-fluctuation parameters are evaluated and the nature of the lowest-lying ionization state is investigated.
Micromagnetic Barkhausen signals from magnetic materials originate from the discontinuous changes in magnetization under the action of a changing applied magnetic field. Barkhausen emissions that are detected by a sense coil come predominantly from a surface layer. In iron based materials this layer is about 500 μm th…