bluuebunny/crossref_metadata_2025_split huggingface dataset:
Static Magnetization Reversal in Thin Films of Co–Ni–P
Authors: Bate G. , Speliotis D. E. , Morrison J. R. 
Published: April 2005

Electrodeposited films of Co–Ni–P containing 14% nickel and 1% phosphorus by weight and having thickness 0.05 to 0.2 μ showed the following magnetic properties—high coercivity (300–550 Oe), high ratio of remanent-to-saturation moment (∼0.90), steep-sided hysteresis loops and isotropy in the film plane.
The process of magnetization reversal was studied by using a sensitive Hall probe to measure and map the horizontal component of the flux above the surface of the film after increasing reverse fields has been applied. This technique was used since neither the Bitter pattern method nor the Kerr effect revealed the natural pattern of magnetization reversal. However, it was possible to introduce, deliberately, a small region of reversed magnetization by means of the field from a magnetic recording head and examine this region by all three methods. This provided a method of checking the interpretations of the Hall effect data.
It was found that these films employ a unique mode of magnetization reversal. Initially, small regions of reversed magnetization are established throughout the film, and these regions grow together to form elongated switched areas whose long dimensions are always perpendicular to the direction of applied field. The reversal pattern is highly reproducible in a given sample for a given field direction and reverses when the field direction reverses.
This switching behavior is dependent on the direction of the field with respect to the sample, the long direction of the reversed regions always being perpendicular to the applied field. The sign of the vertical component of the flux from the sample was compared above and below the sample to determine whether magnetization perpendicular to the film plane existed. No such regions were found with a Hall probe of sensitive area down to 25×25 μ.
Photon Avalanches from a Population Inversion
Authors: Tonks Lewi 
Published: April 2005

High-power lasers encounter increasing losses of stored energy from stimulated emission by once-through avalanches of photons as higher powers are sought. This occurs even without resonance buildup. Even in the simple geometry of a thin rod, a satisfactory analysis would require elaborate machine calculation. A very crude model has, however, produced rough results from which some guidance is obtainable.
The model exhibits the expected linear increase of outgoing photon flux near the end of the rod and the huge depletion of excited atom population away from the rod equator. A criterion has been developed for the maximum useful excitation relative to emission parameters, rod length and rod cross section. It is concluded that this excitation level is fairly insensitive to aspect ratio (radius/length) but that internal reflection from the rod cylindrical surface can markedly lower this level by increasing the effective aspect ratio enormously.
Determination of Particle Structure from Light Scattering
Authors: Hart R. W. , Gray E. P. 
Published: April 2005

Light scattering is well known as a useful tool in the investigation of the structure of particles. One of the disadvantages is that, whereas the scattering often may be calculated for a given structure, it has not been possible to carry out a Fourier inversion of the scattered intensity function to determine an unknown structure.
There are two major difficulties which are immediately recognizable. (1) The phase as well as the amplitude of the scattered radiation must be measured, and (2) the usual technique of Fourier inversion is not applicable because it requires knowledge of the scattered wavefunction for experimentally unattainable values of parameters. Both of these problems are discussed, and it is noted that they may be overcome in certain cases of interest. A method of phase determination suited to optical wavelengths is suggested for scattering by a single particle. Further, for ``soft'' scatterers, a method of inverting the scattering data is developed that does not suffer from the difficulty associated with the Fourier method. Thus, the inversion may be carried through and the desired structure of a scatterer may be obtained.
Stacking Fault Nucleation in Epitaxial Silicon on Variously Oriented Silicon Substrates
Authors: Mendelson S. 
Published: April 2005

Epitaxial growth of silicon is studied for seven low-index orientations of the silicon substrate. Stacking fault traces are observed on all growths in both the single line and polygonal forms, the latter being dominant in the better growths. For each orientation the largest uniform size stacking fault polyhedra nucleate on the substrate surface and have traces on the film surface with dimensions directly related to the film thickness through a geometric factor. This factor is computed by taking the bounds of the faults (which lie in {111} planes) as 〈110〉 directions.
Direct observations are presented to show that stacking faults form at slip lines, at microscratches produced in the polishing procedure, at particles on the substrate surface, at regions of localized impurity segregation, at surface oxides, and at cleaning stains. Most of the faults can be removed by annealing in hydrogen but not in argon. Among mechanically polished substrates, {111} substrates have the highest stacking fault density. No orientation effect is observed for growths on chemically polished substrates. The effects are consistent with nucleation by small incorrectly deposited two-dimensional layers and by the presence of a foreign substance (probably an oxide) on the substrate surface; the model attributing stacking fault nuclei to collapsed vacancy disks is highly unlikely.
Ion Optics of Fields with Rotational Symmetry and Circular Main Orbit
Authors: Boerboom A. J. H. 
Published: April 2005

Part I. First-order theory of fields with an axis and a plane of symmetry. By using a symmetry property of the ion orbits in magnetic or electric fields with rotational symmetry, the ion optics inside these fields can be simply deduced. The physical meaning of the various terms in the expressions for the ion orbits is clarified. First-order imaging properties are derived.
Part II. First-order theory for the general case. The calculations on the ion optics of fields with an axis and a plane of symmetry are generalized by omitting the requirement of the symmetry plane. The trajectories in the field are calculated up to the second order. The general equation of the ion path is given by r−R=Σ akl cos[k(αw+[open phi])+l(γw+ψ)]z=Σ ckl cos[k(αw+[open phi])+l(γw+ψ)].The first-order imaging properties are discussed.
Part III. Second-order theory of configurations of consecutive fields and the principle of object aberrations. The method is extended to calculate the ion paths up to the second order in instruments having one or more fields with a plane and an axis of symmetry. By introducing the concept of optical aberrations in the object, the calculation of higher-order aberrations can be simplified to a large extent.
Cataphoresis in Helium-Neon Mixtures
Authors: Schmeltekopf Arthur L. 
Published: April 2005

Cataphoresis in He-Ne mixtures was studied spectroscopically and the measurements checked by mass spectroscopy. The pressure was varied from 6 to 90 Torr, the wall temperature from 30° to 500°C, and the current from 10 to 500 mA in quartz tubes of 9.52 and 12.7 mm diameter. The results are compared with the theoretical predictions of Druyvesteyn. Cataphoresis improves with increasing pressure, as predicted, except at pressures above 40 Torr, where the quality of cataphoresis improves only slowly with pressure. The slope of the impurity concentration curve does not change linearly with current from 20–100 mA; it increases with current at very low currents and then becomes independent of current. Because of this discrepancy between theory and experiment, a new empirical equation governing cataphoresis in the region of higher currents is suggested. An increase of temperature markedly decreases the effectiveness of cataphoresis. Increasing the tube diameter and decreasing its length also decreases the effectiveness.
In order to check for a possible ``retrograde'' cataphoresis some measurements were made with He as a minor constituent in Ne. Spectroscopic observations at the cathode indicate an enhanced He concentration there (retrograde cataphoresis); mass spectroscopic analysis shows that the cataphoresis, while slight, is still normal. The extreme excitation conditions at the cathode render spectral intensity interpretations difficult if not misleading there.
Quantitative Calculation of the Magnetic Ripple of Uniaxial Thin Permalloy Films
Authors: Hoffmann Horst 
Published: April 2005

The magnetic ripple of thin films with uniaxial anisotropy is calculated for the field and the magnetization lying along the easy and the hard direction of the uniaxial anisotropy. For small dispersion of the direction of magnetization, the variational principle, applied to all energy terms including the exchange, crystalline anisotropy, uniaxial anisotropy, magnetostriction, magnetostatic, and stray field energies, yields a Bessel's differential equation. Its solutions (cylindrical functions) describe the two-dimensional magnetic ripple of the film. Along the mean direction of the magnetization the fluctuations of the magnetization vector are much greater than perpendicular to it. In the first case these fluctuations are coupled by exchange forces, and in the second case by the stray field. The dispersion of the magnetization depends on the dispersion of the anisotropy, on the magnetic constants of the film, on the thickness of the film, and on the applied field. The theory is able to explain the image of the ripple observed by the electron microscope and to explain the variation of the ripple quantitatively, if the applied field is varied. The estimation of the mean magnetization dispersion agrees with the experimental data of Fuller and Hale. The statements of the theory concerning the mean wavelength λ of the ripple for the mean direction of magnetization along the easy axis λL=2πA12Ku−12(hL+1)−12,and along the hard axis λs=2πA12Ku−12(hs−1)12,are verified by experimental observations. (A is the exchange constant, Ku the uniaxial anisotropy constant, hL = HL/Hk is the reduced field along the easy axis, hs = Hs/Hk is the reduced field along the hard axis.) The calculated domain width, occuring at magnetization reversal along the hard axis, is in good agreement with the experiments of Middelhoek, Feldtkeller, and Smith. The domain splitting is fine at a great dispersion of the anisotropy axis and is less fine at smaller dispersions. The smallest domain width of 80–20 Permalloy films is of the order of 2 μ.
Furthermore the theory gives a new method for the determination of the anisotropy field strength Hk.
Calculation of the Current and Field Distribution and the Magnetization Curves for High-Field, Superconducting Materials in the Form of Sheet
Authors: Riemersma H. 
Published: April 2005

This paper determines the field and current distribution in a high-field, superconducting material in sheet form, where the applied magnetic field is parallel to the sheet. The distributions are obtained from a critical state equation and Maxwell's equations, and determined for the two cases of absence or presence of a net transport current in the material.
The field distributions are used to determine the magnetization of the material as a function of applied magnetic field, with the short-sample current-carrying capacity as a parameter. The zero transport current magnetization curves show good agreement in general shape with those experimentally observed. The analysis indicates a reduction in magnetization with increasing transport current.
Elastic Constants of Aluminum
Authors: Vallin J. , Mongy M. , Salama K. , Beckman O. 
Published: April 2005

The adiabatic elastic constants of aluminum have been measured with an ultrasonic pulse technique at liquid-heluim, liquid-nitrogen, and room temperatures. The values of the elastic constants at 4°K are c11=11.63, c12=6.48, and c44=3.09 in units of 1010 N/m2. The Debye characteristic temperature calculated from these figures is θ=425°K in good agreement with the value obtained from speciffic heat data.
The shear elastic constants ½(c11−c12) and c44 are discussed with reference to the theory given by Leigh.
Diffusion Mechanism of Zn in GaAs and GaP Based on Isoconcentration Diffusion Experiments
Authors: Chang L. L. , Pearson G. L. 
Published: April 2005

Precise relationships between the diffusion coefficient D and the zinc concentration C are obtained from isoconcentration diffusion experiments performed at 900°C for zinc in GaAs and at 1000°C for zinc in GaP. It is found that D varies with C from a slightly less than cubic to a somewhat less than square dependence over the concentration range 1018 to 1020 cm−3.
Possible mechanisms that result in concentration-dependent diffusion are discussed. Under the conditions given above, it is concluded that diffusion occurs by an interstitial-substitutional mechanism with the interstitial mode being dominant. The charge states of the various species involved in the diffusion are believed to be: (1) interstitial zinc atoms are doubly ionized donors; (2) substitutional zinc atoms are either neutral or singly ionized acceptors; and (3) gallium vacancies are neutral. A theoretical expression for D versus C, derived under these assumptions, fits the isoconcentration diffusion data over wide ranges of D and C through the use of only one adjustable parameter.
X-Ray Measurements of Faulting in α Cu-Ge Alloys
Authors: Vassamillet L. F. , Massalski T. B. 
Published: April 2005

The shifts of the (111) and (200) x-ray diffraction lines have been measured by both the centroid and the peak method. From these measurements the stacking fault probability α and the twinning fault probability β can be obtained on powdered samples prepared by filing. These results show a parabolic type of dependence of α with composition, whereas the stacking fault probability α obtained from previous measurements using the same technique on Cu-Zn and Ag-Cd alloys had a linear dependence with composition.
By means of a simple argument the relative stacking fault energies for these alloys can be deduced and compared with those obtained on similar Cu-Ge alloys by Howie using thin-film electron microscopy and by Haasen and King using tensile tests.
Generalized Thermal J-V Characteristic for the Electric Tunnel Effect
Authors: Simmons John G. 
Published: April 2005

The thermal J-V characteristic for a tunnel junction is derived in terms of a generalized theory. The resulting functional form of the equations is similar to that of Stratton; however, in the present formulation, the physical parameters of the junction appear explicitly, and their effect upon the thermal characteristic is readily appreciated. In Stratton's work, the physical constants appear in the integrand of integral that can be solved only numerically.
The theory is applied to symmetric and asymmetric junctions. For the symmetric case, it is shown that, at a given temperature, the percentage change Ĵ in the high-temperature thermal component of current from the low-temperature value increases initially with increasing voltage bias up to a maximum peak, and thereafter decreases rapidly. The voltage bias at which the component of thermal current maxima occurs is equal to the interfacial barrier height and, as such, permits what is probably the most accurate method of barrier height determination. Similar results are obtained for the asymmetric barrier; however, in this case, Ĵ depends upon the polarity of the voltage bias for V&gt;φ1, and two Ĵ maxima occur at voltages corresponding to the two distinct interfacial barrier heights φ1 and φ2.
Dislocation Contribution to the Second Harmonic Generation of Ultrasonic Waves
Authors: Hikata Akira , Chick Bruce B. , Elbaum Charles 
Published: April 2005

The experimental evidence and the associated theory are presented for the dislocation contribution to the generation of the second harmonic of an ultrasonic wave in solids. The contribution is measured through the changes, as a function of static bias stress, in the amplitude of the second harmonic of a fundamental wave (10 Mc/sec compressional wave) propagating in the specimen.
In aluminum single crystals the amplitude of the second harmonic, for a given amplitude of the fundamental, changes markedly with static bias stresses ranging from 0 to 106 dyn/cm2. In alloys, there are essentially no changes of the amplitude of the second harmonic even for bias stresses up to 107 dyn/cm2. These observations are consistent with the predicted dependence of the amplitude on dislocation loop length and on the static stress. The effects of small amounts of plastic deformation were consistent with the proposed model.
Diffusion of Copper in Nickel and Aluminum
Authors: Anand M. S. , Murarka S. P. , Agarwala R. P. 
Published: April 2005

Diffusion of copper in nickel and aluminum has been studied by the residual activity technique in the temperature ranges of 850° to 1050°C, and 350° to 630°C, respectively. Diffusivities (cm2/sec) are expressed as DCu/NiCu/Ni=0.724 exp[−(61 000/RT)]DCu/AlCu/Al=0.150 exp[−(30 200/RT)].
Results have been compared with those calculated from the theories of diffusion based on charge and size difference between the impurity and the solvent atoms.
Gas Velocity Probe for Moving Ionized Gases
Authors: Cason Charles 
Published: April 2005

A direct electrical method for measuring the velocity of a flowing plasma is based upon the polarization voltage induced when a plasma flows transversely to an applied magnetic field. A method has been developed to allow the estimation of certain background signals and the determination of allowable measurement currents arising from plasma and probe properties. Applications for this technique of ionized gas velocity measurements are indicated.
It was found that an ac magnetic field of the order of 5 G would give a sufficient signal to determine the gas velocity of a plasma jet as compared to a dc field of the order of 100 G. Gas stream velocities produced by a low-power argon plasma jet were found to vary from 1000 to 3000 m/sec depending slightly on the mass flow rate and predominantly on the ambient pressure.
Improved Thermionic Emitter: Thorium on Grain-Oriented Polycrystalline Tungsten
Authors: Weissman Ira 
Published: April 2005

A grain-oriented polycrystalline thoriated tungsten emitter is described which demonstrates vastly improved emission characteristics over ordinary emitters of the same type.
The factor of four improvement in electron emission in high vacuum is almost entirely the result of an increase in A value from four to seventeen. The Richardson work function φ of the improved emitter is essentially the same as that of the ordinary one.
A comparison is made of the efficiencies of two cesium-neutralized thermionic converters, identical in every respect except that one contains the improved emitter and the other an ordinary one. The measured improved factor of three in conversion efficiency is in close agreement with the predicted factor based on the difference in A values.
Nature of Rectifying Junctions in α-Silicon Carbide
Authors: Griffiths L. B. 
Published: April 2005

Rectifying junctions have been prepared in α-SiC during crystal growth, from chromium solution, over a temperature range from 1700°–1900°C. From an observed systematic variation of junction capacitance at zero bias, with growth temperature, an effective diffusion coefficient Deff was computed. The temperature dependence of Deff yields an activation energy of 4.8 eV. This value is compared to an independently determined value of 4.9 eV for the diffusion of aluminum in αSiC. It is concluded that the structure of these junctions is dependent upon interdiffusion of the major dopants and therefore upon the temperature of crystal growth.
The form of the experimentally determined forward current—voltage characteristics is shown to be in general agreement with the foregoing model.
Anion Diffusion in Crystals of NaCl
Authors: Barr L. W. , Morrison J. A. , Schroeder P. A. 
Published: April 2005

Diffusion coefficients of the chloride ion in NaCl have been measured between 300° and 700°C using an isotopic exchange method. The concentrations of cation impurities were deduced from electrical conductivity measurements over the same temperature range. In the extrinsic region, the diffusion coefficients do not decrease with increasing amounts of cation impurity to the extent required for diffusion by single vacancies.
The general conclusion that diffusion occurs both by single vacancies and by vacancy pairs agrees with that reached earlier by Laurance. Analyses of the experimental results in the intrinsic region yield for single vacancy anion diffusion Da=1.1×e−1.92/kT cm2 sec−1 and for vacancy pair diffusion Dp=363×e−2.37/kT cm2 sec−1, and the activation energies, which are given in electron volts, agree well with theoretical estimates.
Large variations were observed in the anion diffusion coefficients for crystals doped with Ca++; the cause cannot be established definitely.
Stability of the Shape of a Solid Cylinder Growing in a Diffusion Field
Authors: Coriell Sam R. , Parker Robert L. 
Published: April 2005

The stability of the shape of an infinite cylinder undergoing radial growth controlled by diffusion is studied by a method originated by Mullins and Sekerka (MS). It is found that the circular cross section of a cylinder is stable when its radius is less than and unstable when its radius is greater than a certain radius Rc. This result is analogous to the MS result that a sphere is stable below and unstable above a certain radius Rc, which is seven times the critical radius R* of nucleation theory. However, in the present case, the ratio Rc/R* is not equal to seven, but is a function of S=(c∞-cs)/(C-cs), where c∞, cs, and C are the concentrations of the solute at infinity, at the surface of the cylinder, and in the precipitate, respectively.
The case of perturbations in the radius along the length of the cylinder is also treated. Potential application of the result to such problems as the growth of branches on dendrites is discussed.