bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slip-Induced Directional Order in Fe-Ni Alloys. II. Experimental Observations
Authors: Chin G. Y. , Nesbitt E. A. , Wernick J. H. , Vanskike L. L. 
Published: January 2005

The results of an extensive investigation into the nature of slip-induced directional order in Fe-Ni alloys near the 75% Ni composition are reported in this paper. Single crystal rods of 4–79 moly-Permalloy were swaged in the [111] and [001] orientations, as were crystals of the following orientations subjected to plane strain compression: (001) [100], (001) [110], (110) [001], (110) [1̄12], (110) [1̄10], (111) [1̄12], (112) [1̄10] and (112) [1̄1̄1]. Magnetic torque measurements show that all crystals developed a uniaxial anisotropy upon deformation, with the easy magnetic direction in good agreement with our previous theoretical deductions. In the [001] swaged crystal, deviation of the observed easy axis from the calculated value was rationalized in terms of unequal participation of the expected slip systems.
In all cases of plane strain compression, the induced anisotropy constant rose to a maximum value, and then decreased, as the thickness reduction was increased. In one experiment, crystals of a 2%Mo-76% Ni-22%Fe alloy received a long-range-ordering treatment at 475°C for 190 h prior to plane strain compression in the (110) [1̄12] orientation. The anisotropy energy reached a maximum value of 460 000 erg/cm3, the highest value of slip-induced anisotropy thus far reported in Fe-Ni alloys. As for the anisotropy decrease at large reductions, reorientation of slip-induced atom pairs as a result of lattice rotation, is undoubtedly a factor. However, this explanation is not valid for the (110) [1̄12] orientation, which remained stable even after 98% reduction. A more widely applicable mechanism is advanced, whereby the decrease in anisotropy is attributed to randomization of the atom pairs through slip across antiphase ordered domain boundaries, both those grown-in and those created by intersecting slip.
Additional observations have been made of the crystallographic texture and magnetic squareness in cold-formed polycrystalline Permalloy tapes, which are currently used as magnetic memory elements in storage devices. The results are satisfactorily explained in terms of slip-induced directional-order theory. Implications of seeded single crystals to these results are discussed.
Thermal Emission Microscope Studies of Cesium Surface Ionization on Porous Refractory Metals
Authors: Jamba D. M. , Husmann O. K. 
Published: January 2005

Quantitative thermal emission microscope studies of cesium surface ionization on porous tungsten emitters show under clean surface conditions a surface migration length in the 2-μ range. The migration length from the pore exit is under this condition fairly independent of the flow rate per pore and the emitter temperature. It is therefore concluded that 107 pores/cm2 (traverse counting technique) yield maximum ionization efficiency on porous tungsten.
Clean surface conditions were checked by Richardson work function measurements with the built-in Faraday cage. Also, the ion-current transition pattern in the threshold region was used for judgement of the surface condition. In case of a contaminated surface, a smooth transition from high to low ion current with decreasing temperature was observed in contrast to the steep ion-current change-over in the threshold region under clean surface conditions. Also the surface migration length increased on the contaminated surface.
Molybdenum, sputtered onto the porous tungsten substrate, showed a uniform work function over the entire emitter area with φ=4.20 eV.
Space-Charge-Limited Currents in Copper Phthalocyanine Thin Films
Authors: Sussman Alan 
Published: January 2005

Measurements of space-charge-limited currents have been made on evaporated thin films of the compound copper phthalocyanine using Ohmic contacts. A complete study of the current as a function of voltage, temperature, thickness, and illumination indicates that all the results are consistent with the assumption of an exponential distribution of trapping states of the form Nt(E) = kTcP0 exp (E/kTc), where kTcP0 is a parameter related to the total trap density.
Practical techniques for obtaining values for the mobility, density of states, total trap density, trap distribution in the vicinity of the Fermi level, and trap capture cross section are outlined and values reported.
Electrical Properties of Copper Phthalocyanine Thin Films as Influenced by the Ambient
Authors: Sussman Alan 
Published: January 2005

Measurements of currents in evaporated thin films of copper phthalocyanine as a function of temperature and ambient have yielded information about the effects of nitrogen, hydrogen, and oxygen ambients on the conductivity, trap density, and mobility. Above a transition voltage the currents are space-charge-limited and can be correlated with a trap distribution that decreases exponentially with energy as the distance from the valence band edge increases. The parameters that govern the distribution as well as the position of the Fermi level depend on sample preparation, and some systematic correlation exists between annealing and the subsequent values of these parameters, based on consideration of the crystal changes that occurs on heating.
The value of the intrinsic conductivity σ0=3(Ω cm)−1 and mobility μ=0.013±0.007 cm2/Vsec have been determined and are found to be relatively independent of preparation and subsequent treatment.
Time Dependence of Avalanche Processes in Silicon
Authors: Lee C. A. , Batdorf R. L. , Wiegmann W. , Kaminsky G. 
Published: January 2005

An analysis of the time dependence of avalanche processes encountered in silicon junctions, including the effects of different ionization rates and velocities of the two charge carriers, is presented. An earlier analysis of Read was restricted to equal ionization rates and velocities; that restriction has been removed but the frequency limitation of his analysis has been retained here. Various solutions of the generalized differential equation are obtained, including a steady-state solution to a sinusoidal perturbation of the avalanche-field maximum. The important features of this steady-state solution are that it describes the avalanche current for all explicit values of the multiplication M≥1, is valid for highly nonlinear responses to the sinusoidal perturbation, and contains both the in-phase and out-of-phase parts of the fundamental-frequency component of the avalanche response.
The analysis is applied to solid-state photomultipliers, is used to explain an anomalous rectification observed in operating Read structures, and, lastly, the small-signal limit of the avalanche response is compared with susceptance measurements of a uniformly avalanching junction as a function of the multiplication and saturation current over a frequency range of 20 to 200 MHz.
Analysis of the Q Factor, Efficiency, Stability, and the Design of Read Structures in the Nonlinear Range
Authors: Lee C. A. , Batdorf R. L. , Wiegmann W. , Kaminsky G. 
Published: January 2005

Using time-dependent solutions of the avalanche current generalized for unequal ionization rates and velocities of the two charge carriers, compact formulas for the Q and the efficiency of the Read structure are derived, which are valid from zero to very large oscillation amplitudes. A method is developed to properly account for the internal-field adjustment (which may be variably positive or negative) that is caused by the nonlinearly rectified avalanche-current component flowing through the drift region. These developments clearly show that the behavior of the Q at intermediate and large signals cannot be correctly derived unless the avalanche analysis retains terms related to both the in-phase and out-of-phase components of the avalanche current.
The behavior of Q vs oscillation amplitude is numerically calculated for a successfully operated prototype and compared with experimental observation. These experimental observations in conjunction with the analytical development also permit an interpretation and assessment of the effects due to inhomogeneities in multiplication found in junctions.
Design considerations of Read structures are discussed, particularly how various parameters that are critical in optimizing the efficiency and stability may be controlled by design of the electric-field distribution of the avalanche. It is shown how advantage may be taken of the asymmetry of ionization rates of the two charge carriers to achieve even higher efficiencies than the 30% Read predicted for the case of equal ionization rates. Finally, certain circuit criteria for achieving dynamic stability are discussed and solutions given.
Dislocation Configurations in Cylindrical Coordinates
Authors: Owen D. R. J. , Mura T. 
Published: January 2005

General expressions are derived for the stress components due to an arbitrary continuous distribution of dislocations prescribed in a cylindrical coordinate system. Results are obtained for the stress field of a helical dislocation of uniform shape with the Burgers vector along its axis. The additional energy arising from the interaction of a point defect with the helix is obtained and the behavior of the defect examined.
It is also shown how results for circular dislocation loops are readily obtained from the general expressions and in particular the problem of a rotational loop, which is formed by twisting the two faces of the slip surface relative to each other, is solved.
Magnetic Annealing Effects in Silicon-Doped Garnets
Authors: Hunt Robert P. 
Published: January 2005

Many properties of polycrystalline yttrium iron garnet (YIG) and reduced single-crystal YIG have been attributed to the presence of Fe2+ ions which provide mobile electrons that can diffuse locally through the lattice. It was the purpose of this research to study the modification to the low-temperature anisotropy caused by the presence of Fe2+ ions in silicon-doped YIG, Y3Fe5−δSiδO12 with 0&lt;δ&lt;0.18. Silicon-doped YIG demonstrates a time-dependent induced anisotropy proportional to doping when magnetically annealed to low temperatures. The kinetics and temperature dependence of this induced anisotropy have been studied. It is further found that these doped garnets show a constant, high-field component of rotational hysteresis which is both frequency- and temperature-dependent.
The intrinsic, unannealed anisotropy behaves in a novel way. At room temperature the anisotropy coincides with normal YIG, while between 150°K and 300°K | K1 | increases above that of pure YIG Below about 150°K the curves develop asymmetry and appear to be no longer purely cubic. At 4.2°K the easy axis has shifted to the [100] direction (&gt;3% doping) indicative of a change in sign in K1. Silicon-doped lutetium iron garnet and polycrystalline lutetium iron garnet were found to behave in a similar manner.
The results are interpreted in terms of an electron-diffusion model which enables the Fe2+ ion to effectively wander among four nonequivalent octahedral sites. A simple kinetic rate theory is at least partially successful in explaining: (1) the time dependence of the torque curves, (2) the rotational hysteresis, and (3) some of the apparent low-temperature deviations from cubic symmetry.
Current Transport and Maximum Dielectric Strength of Silicon Nitride Films
Authors: Sze S. M. 
Published: January 2005

Measurements of current-voltage characteristics have been performed on Au-Si3N4-Mo and Au-Si3N4-Si (degenerate substrate) structures of various nitride-film thicknesses from 300 Å to 3000 Å and over a range of temperatures. The films are deposited by the process of reaction of SiCl4 with NH3. It is found that at any given temperature and electric field, the current transport is essentially independent of the substrate material, the film thickness, or the polarity of the electrodes.
It is proposed that the current-transport mechanisms are bulk controlled rather than electrode controlled. The conduction-current density, J, is the sum of three contributions: J = J1+J2+J3, where J1∼E exp {−q[φ1 − (qE/πε0εd)½]/ kT}, J2∼E2 exp (−E2/E), and J3∼E exp (−qφ3/kT). At high fields and high temperatures J1 dominates the current conduction (the Poole-Frenkel effect or internal Schottky effect); one obtains a barrier height of (1.3±0.2) V for φ1 and a value of 5.5±1 for the dynamic dielectric constant εd. At high fields and low temperatures J2 dominates as a result of field ionization of trapped electrons (presumably from the same centers as for J1) into the conduction band; one obtains a value for the field E2 of the order of 6×107 V/cm. At low fields and moderate temperatures J3 dominates because of the hopping of thermally excited electrons from one isolated state to another yielding Ohmic characteristics and a thermal-activation energy qφ3 of about 0.1 eV.
At low temperatures the maximum dielectric strength approached ∼107 V/cm. At high temperatures where J1 dominates the current conduction, the maximum dielectric strength, which is limited by thermal instability, decreases as (φ1 − CT)2, where C is a function of the thermal conductivity of the nitride films.
Recoil of Fission Products in Homogeneous Carbon Structures
Authors: Evans R. B. , Rutherford J. L. , Perez R. B. 
Published: January 2005

An experimental investigation of the average range of fission fragments in pyrolytic graphite was performed by exposing coupons of this material bearing a thin electromagnetically deposited layer of 235U to thermal neutrons. For the experiments, reliable and reproducible sectioning techniques were developed for the determination of ranges in thick targets with variable structure. The procedures used to obtain the range average in terms of the experimental data are described in detail, and an empirical formula for the calculation of ranges in pyrocarbons is given.
Analytical expressions were generated for describing the penetration of the recoil-fission fragments in the target material and evaluating various theoretical models of electronic and nuclear-stopping mechanisms in a reference structure. It was found that for carbons of homogeneous structure and with void sizes smaller than Bohr's straggling parameter, the penetration curves could be obtained as convolutions of a kernel of the form of a normal-distribution curve. For the thin extended sources used in this investigation, the various integrations performed mitigate straggling effects so that the only important parameter for data correlations is the average range, which was obtained for four mass chains in six different experiments. The values so obtained compared favorably with Lindhard's and Frank's microscopic models for the calculation of the average range in carbon.
Interaction between a Magnetic Field and a Plasma Flow Behind a Shock Wave
Authors: Kuriki Kyoichi 
Published: January 2005

A theoretical calculation is made from which the electrical conductivity or magnetic Reynolds number of a shock-produced plasma flow can be derived. The results of the analysis predict the effects of the transient magnetic field induced by the interaction between the applied magnetic field and the plasma flow behind a shock wave. The applied magnetic field considered is transversal to the flow. Its intensity is either steady in time and increasing linearly in the flow direction or spatially uniform but increasing linearly with time.
If the applied field extends to infinity, the intensity of the induced magnetic field is proportional to the magnetic Reynolds number and to the intensity of the applied magnetic field. With the aid of the present analysis the magnetic Reynolds number can be determined by comparison of the measured field and the calculated magnetic field. This method is applicable even if the magnetic Reynolds number is greater than unity. The effects of the finiteness of the applied field are considered.
Thermal Conductivity and Heat Capacity of the Monocarbide, Monophosphide, and Monosulfide of Uranium
Authors: Moser J. B. , Kruger O. L. 
Published: January 2005

The heat-transport properties and heat capacity of UC, UP, and US were determined between room temperature and 600°C. These properties were measured by a transient technique with a laser as a heat pulse source. The thermal conductivity was calculated from the product of the thermal diffusivity, heat capacity, and density. At room temperature the thermal conductivity of the three compounds corrected to theoretical density was found to be 0.057, 0.033, and 0.021 cal sec−1 cm−1°C−1 for UC, UP, and US, respectively. At 600°C the value for UC decreased to 0.041 cal sec−1 cm−1°C−1. The thermal conductivity of UP remained equal to its room-temperature value and that of US increased to 0.029 cal sec−1 cm−1°C−1. The room-temperature heat capacity values for the three compounds investigated were all slightly above 12 cal mole−1°K−1. At 600°C the heat capacity of UC increased to 15.2 cal mole−1°K−1, whereas no appreciable changes were found for UP and US at this temperature. The experimental heat-capacity values were used to formulate expressions of the type Cp=a+bT+cT−2 with the aid of a computer program, and enthalpies and entropies of the compounds were calculated from 400° to 1000°K.
The electronic contributions to the thermal conductivities of the three compounds were calculated by means of the Wiedemann-Franz law with the Lorenz constant for metallic conductors. The limitations of this approach are discussed and an alternate method of separating the phonon from the electronic part of the thermal conductivity is presented. A value of 0.02 cal sec−1 cm−1°C−1 for the lattice conductivity alone was obtained. This value is close to the 0.01 to 0.02 cal sec−1 cm−1°C−1 obtained by using the Wiedemann-Franz law on UP and US. The thermal conductivity of UC above 300°C can be ascribed to electrons if the traditional Lorenz constant is used. However, comparison of the thermal and electrical conductivity for the three compounds indicates that the Lorenz number when applied to UC should be lower, possibly because of the presence of optical scattering. It was found that the lattice resistance to the flow of heat in this group of compounds is essentially temperature independent and that calculations based on the classic models do not give good agreement with measured values.
Deformation Theory of Hot-Pressing
Authors: Kakar Ashok K. , Chaklader A. C. D. 
Published: January 2005

The possible deformation behavior of spheres in a compact has been both theoretically analyzed and experimentally verified. The change in contact area radius a relative to the particle radius R has been related to the bulk density and bulk strain for four possible modes of packing: simple cubic (Z=6), orthorhombic (Z=8), rhombohedral (Z=12), and body-centered cubic (Z=8).
An equation relating the above parameters can be represented by D−D0=32D0(a/R)2 for different types of packings, D and D0 being densities at any a/R and a/R=0, respectively. It has been shown experimentally by deforming lead spheres at room temperature, 50° and 100°C in a cylindrical die, that the over-all deformation is similar to that of the orthorhombically packed monosized spheres. A change in the coordination number Z during the deformation process was also observed and may account for the deviation from the theoretically predicted values.
Similar experiments using sapphire spheres were carried out in the temperature range 1570°–1700°C, and the results showed that the deformation behavior was very similar to that of the lead spheres.
Permeability of Some Oxides and Metals at Low Temperatures
Authors: Van Groenou A. Broese 
Published: January 2005

Low-temperature measurements are reported on the initial permeability (μ) of a number of polycrystalline MnZn- and NiZn-ferrites and yttrium iron garnet. In the temperature range of liquid helium, the unsubstituted samples of YIG, NiZn-ferrite, and MnZn ferrite show a μ value of about 60. A time dependence of μ after demagnetization was observed for these samples.
Alloys of composition NixFe1−x show much higher values of μ. At 4°K for x=0.5, a value of μ=3000 is found, together with a coercive force of 0.3 Oe. For x=0.35 and 0.40, a threefold increase in μ is observed between 4° and 20°K. The other alloy samples all have a temperature-independent permeability up to 100°K.
Diffraction Effects in Lorentz Microscopy
Authors: Wohlleben Dieter 
Published: January 2005

Several electron optical techniques are in use to study microscopic magnetic field distributions through deflection by the Lorentz force (Lorentz microscopy). It is shown that for most cases of practical interest the deflected electrons must be treated quantum mechanically in order to extract quantitatively information on the structure of the field inhomogeneity from the experimental electron record. The lateral wave-length of an electron deflected in a weak magnetic field is independent of the initial electron momentum and is often of the order of the lateral extent of the structure under investigation. For instance, in ferromagnetic thin films, λlat≈1000 Å behind domain walls 3000 Å wide, or λlat≈10 μ behind ripples with 2 μ period. It is well known that the geometric approach to contrast formation can break down in such cases (Abbe's sine condition).
High-resolution micrographs of ferromagnetic layers are shown. In the defocused mode, one interference fringe appears in the image per flux unit h/2e in the layer near convergent walls. In the Foucault mode, the transition from bright to dark areas of the image occurs across a finite distance due to diffraction. This distance corresponds to the width of one flux unit h/2e in the layer.
Ripple contrast is smaller than one and is a complicated function of defocusing distance, ripple period, and initial electron momentum due to diffraction. High-frequency-ripple Fourier components tend to be damped in the image, and certain components cannot at all produce any contrast.
Lorentz contrast from the Abrikosov lattice in hard superconductors is expected to be qualitatively similar to, but weaker than, ripple contrast. The Foucault mode is shown to be inferior to the defocused mode for quantitative high-resolution Lorentz microscopy.
The Non-Self-Similar Propagation of a Thermal Radiation Front
Authors: Parks D. E. 
Published: January 2005

The non-self-similar diffusion of energy from an enclosure is investigated for plane parallel geometry for the case where the transport of energy is purely radiative. The energy released instantaneously in the cavity is partitioned in arbitrary proportions between radiant energy and internal energy of matter. The mean free path of radiation in the walls bounding the enclosure varies as the cube of the temperature, but the material within the enclosure is assumed to be transparent to radiation.
Solutions for the non-self-similar radiative diffusion of radiation from the cavity are expressed in parametric form and numerical results are displayed graphically. In addition, series solutions are given which apply in the limit of short and long times after the initial release of energy in the cavity.