bluuebunny/crossref_metadata_2025 huggingface dataset:
Stacking Fault Probabilities of Some Alloys of Copper and Silver with Zinc and Cadmium
Authors: Vassamillet L. F. , Massalski T. B.
Published: April 2005

The deformation stacking fault probability has been measured by means of x-ray diffraction in a series of Ag-Cd alloys and additional measurements were done on some Cu-Zn and Ag-Zn alloys. The results obtained for Ag-Cd alloys are, within the experimental error, the same as those for Ag-Zn alloys.

If the reciprocal of the faulting probability is assumed to be proportional to the stacking fault energy, the obtained curves relating stacking fault energy with composition in the systems Cu-Zn and Ag-Zn are very similar to those derived by Howie and Swann who used electron microscopy. A comparison of the results from the x-ray and electron microscopy experiments suggests that the stacking fault energies of pure copper and silver are 67±17 ergs/cm2 and 14±3.5 ergs/cm2, respectively.
Beam-Plasma Discharge: Buildup of Oscillations
Authors: Getty W. D. , Smullin L. D.
Published: April 2005

Plasma electron heating was accomplished by exciting plasma oscillations with a pulsed, 10-kV, 1-A electron beam drifting in a longitudinal magnetic field of 100 to 1000 Oe. The oscillatory energy gained by plasma electrons leads to an increase in their density and mean kinetic energy. The resulting plasma, which is called the ``beam-plasma discharge,'' is an rf discharge in which a beam-plasma interaction generates the rf fields.

At the beginning of a beam pulse, beam electrons generate a plasma by ionization of the background gas. Within a few microseconds excited plasma electrons become the dominant ionization source. This paper describes the transient rf oscillations that appear in the first few microseconds of the beam pulse. From a detailed study of this transient it was concluded that a nonconvective instability initiates the oscillations, which first appear at the electron cyclotron frequency, and that a convective instability at the plasma frequency generates the oscillations that sustain the discharge.
Analysis of Wave Propagation in a Magnetoplasma-Filled Waveguide
Authors: Willett Joseph E.
Published: April 2005

A method is developed which permits a two-fluid analysis of wave propagation in a magnetoplasma-filled waveguide including the effects of Hall field, current inertia, space charge, unequal electron and ion temperatures, and diffusion. Maxwell's equations and the two-fluid equations expressed in one-fluid notation are reduced to a pair of coupled wave equations for the longitudinal components of the electromagnetic field. Approximate solutions are obtained for uncoupled TE and TM modes of propagation in a hydromagnetic waveguide. Included is a discussion of the effects of pressure, resistivity, displacement current, and current inertia on the dispersion relations.
Cathode Particle Vapors in a Glow Discharge in Pulsed Diodes
Authors: Worrell Francis T. , Pike H. Alan
Published: April 2005

In the glow discharge in test diodes pulsed at high voltages and high duty cycles, spectroscopic analysis shows the presence of Ba, Sr, and Ca. It is concluded that the discharge is supported by vapors originating in particles of cathode material on the anode.
Temperature Dependence of Ejection Patterns in Ge Sputtering
Authors: Anderson G. S. , Wehner G. K. , Olin H. J.
Published: April 2005

Atom ejection patterns from the Ge (100) and (110) surfaces have been studied for 100–800 eV Ne+, Ar+, Kr+, and Xe+ ion bombardment as a function of target temperature in the range 0°–350°C. For ion energies below a critical value dependent on the bombarding ion, atom ejection patterns are always observed; while for higher bombarding energies the patterns appear only when the target temperature exceeds a certain value. From these data an activation energy of 1.3 eV for diffusion of defects was obtained. The experimental results indicate that very little damage to the lattice results from ion bombardment when the ion energy stays below a critical value (Ar, Ne: ∼200 eV; Kr, Xe: ∼400 eV). At higher ion energy the damage becomes more severe and higher target temperatures are required for annealing the damage between subsequent ion collisions.
Secondary Electron Production from Alpha Particles Emerging from Gold
Authors: Anno James N.
Published: April 2005

The secondary electron yield due to polonium-210 alpha particles emerging from a thin gold surface layer was determined to be 9.2 for an average alpha-particle charge of 1.86. This result is consistent with yield observations with other high energy charged particles. The ratio of the yield due to fission fragments at normal incidence coming from UO2 coatings to the yield due to alpha particles at normal incidence coming from gold was found to be about 20, substantiating the assumption that the secondary yield is proportional to the mass stopping power of the target material. A weak dependency of the yield on electric field was observed; an increase of approximately 8% resulted from a field of 3×105 V/m. A slightly more pronounced field dependency was observed for the yield from fission fragments.
Scattering Factors and Other Properties of Low-Energy Electron Diffraction
Authors: Lander J. J. , Morrison J.
Published: April 2005

Improved low-energy electron diffraction equipment which yields better resolution and a proper background is described. The equipment is sufficiently flexible for measurements of total elastic and inelastic backscattering, and this is illustrated with several examples.

Elastic and inelastic scattering factors are considered and illustrated by experimental data. Since they are complex, complicated, and only semiquantitatively understood, precise surface structure analysis is generally not possible at the current stage of development of this technique, though it now provides a very powerful method for characterizing surface structures. Various approximate methods for interpreting diffraction data are outlined. A preferred approach to a dynamic theory is also discussed.

Other physical properties such as Fresnel zone corrections, Lorentz factors, effects of contact potential, properties of diffraction by two-dimensional gratings, properties of averages, specimen orientation effects, effects of steps, and thermal disorder are considered and illustrated. The analytical results for x-ray and high-energy electron diffraction are sueful but sometimes not directly applicable.
Fluctuation of the Object in Electron Diffraction
Authors: Yamaguchi S.
Published: April 2005

A mechanical fluctuation like Brownian motion takes place for colloidal particles of MgO and ZnO (particle size: 1000×1000×1000 and 5000×500×500 Å3) in a steady flow of electrons (10−5 A/cm2). This is observable as a broadening of the reflections in the electron diffraction patterns obtained with a satisfactorily short wavelength (0.026–0.028 Å).

The mean free path of MgO particles in recoil arising from collision with electrons was about 0.7 Å.

The observations permit not only the measurement of the mean weight of colloidal particles, but also demonstrate the quantum mechanical uncertainty principle.
Oscillatory Tunneling Current through Thin-Film Insulating Barriers in a Magnetic Field
Authors: Goldberg N. , Pollack S. R.
Published: April 2005

The tunneling current between two conductors through an intermediate thin-film insulating barrier in the presence of a magnetic field parallel to the direction of tunneling has been calculated. It is shown that the Fowler—Nordheim tunnel current decreases as the magnetic field is increased and, in certain cases, contains a component which oscillates with a period proportional to 1/H. The oscillations should be observable when the electrons in the material from which the electrons tunnel have a small Fermi energy, a small effective mass, and a long relaxation time. Bismuth, lead telluride, and graphite are examples of materials in which the criteria for observing oscillations are realized.
A Model for a Diffusive Magnetothermoelectric Generator
Authors: Riddiford A. W. , Krumhansl J. A.
Published: April 2005

The energy equation governing a diffusive generator of Cartesian geometry is derived for a z component of uniform magnetic field only and for currents and driving forces in the x-y plane only. The kinetic coefficients may depend on temperature in any manner. Only the induced magnetic field is neglected. Steady state is assumed. Heat is forced to flow in the y direction and current is allowed to flow in the x direction. By assuming no current in the heat flow direction, and no temperature dependence in the current direction, the current is eliminated from the energy equation, which is then the differential equation for the temperature distribution with arbitrary temperature dependence of the coefficients. The exact temperature and current profiles and the efficiency expression are then worked out in analytic form for temperature-independent coefficients. The magnetic-field dependence of the coefficients is then calculated assuming classical statistics, and a single carrier. Numerical integrations are done only for scattering by ions. The upper limit of the efficiency is displayed for various magnetic field strengths as a function of driving-temperature differences.
Thermoelectric Figure of Merit in Silver Selenide Powders
Authors: Epstein A. S.
Published: April 2005

The thermoelectric figure of merit of silver selenide powders prepared by a low-temperature process is examined. By careful attention to the process variables including the compaction, sintering temperature, and cooling rate through the β2 phase it is possible to obtain an n-type thermoelement having a figure of merit of 3×10−3 per degree at room temperature.
Laue Patterns and Zone Structure of Bi2Te3
Authors: Soonpaa H. H.
Published: April 2005

It is shown how Laue x-ray diffraction patterns reveal crystal symmetry and Brillouin zone structure, which can be related to the energy ellipsoid structure derived from galvanomagnetic measurements. Numerical agreement is found between the angles of tilt of the energy ellipsoids from galvanomagnetic data and the angles of tilt of zone faces from x-ray crystallography data.
Pipe Diffusion in LiF
Authors: Tucker R. , Laskar A. , Thomson R.
Published: April 2005

Impurity diffusion of Na ions along dislocations in LiF has been studied by both dc and transient techniques. The Na impurity is injected into the LiF by plating NaCl on one surface of the LiF and placing a potential across the crystal at an elevated temperature. Large-scale diffusion with Na dendrite formation is observable in a dc arrangement and the diffusion can be measured by either radioactive tracer methods or measurement of charge transport. Transient experiments yield an activation energy for diffusion of approximately 0.3 eV for both edge and screw dislocations, and D0=0.01 cm2/sec. Analysis of the charge effects in the core of the dislocations leads one to propose a very large vacancy density in the core, and the experiments are even best understood in terms of a hollow of atomic dimensions along the dislocation core.
Ultrasonic-Refraction Shutter for Optical Maser Oscillators
Authors: DeMaria A. J. , Gagosz R. , Barnard G.
Published: April 2005

Recent interest in the application of infrared and optical masers (lasers) for range measurement, surveillance, welding, and drilling has focused attention on the problem of obtaining high peak-power pulses of short duration and fast risetime from these quantum devices. Kerr cells, Pockel cells, rotating disks, and mirrors have been used as shutters in the past with varying degrees of success. In this paper, experiments are described that demonstrate an ultrasonic shutter suitable for obtaining giant pulses from a ruby optical maser by utilizing the refraction resulting from the passage of a plane-parallel light beam through an ultrasonic field whose wavelength is much larger than the width of the light beam. Amplitude, risetime, and pulse duration are comparable with the values reported utilizing a Kerr cell and superior to those reported for rotating mechanical shutters. In addition, the ultrasonic shutter can be utilized to synchronize the usually random output pulses of a ruby optical maser with the ultrasonic frequency.
Theoretical Shape of Metal-Insulator-Metal Potential Barriers
Authors: Geppert D. V.
Published: April 2005

The shape of metal-insulator-metal potential barriers is derived, including the effects of space charge. For very thin insulating films, the barrier is shown to be essentially rectangular (or trapezoidal if different metals are used on either side of the insulating film). The modification in the rectangular barrier introduced by image forces is derived and shown to be significant for very thin insulating films. Finally, the effect of insulator doping on barrier shape is considered.
Spectral Characteristics of Exploding Wires for Optical Maser Excitation
Authors: Stevenson M. J. , Reuter W. , Braslau N. , Sorokin P. P. , Landon A. J.
Published: April 2005

As pulsed light sources, exploding wires can be used to provide intense narrow spectral lines as well as the characteristic continuum of very high temperature blackbodies. The surface brightness depends on the wire material and conditions under which the wire is exploded. Optimum conditions for 100–500-μsec long light pulses from wires exploded in air have been found for tungsten, tantalum, and molybdenum wires 0.005 to 0.010 in. in diameter for energy inputs of 3000 J or more. Wires exploded in small diameter vacuum tubes (1–20 μ of Hg) radiate as blackbodies, but narrow line spectra are produced in enclosures of larger dimensions. In the visible and ultraviolet regions of the spectrum the spectral radiance of air-exploded wires is one to three orders of magnitude greater than that of conventional flash lamps. Vacuum-exploded wires have spectral radiance another factor of eight greater. Excitation of various optical masers with exploding wires is discussed.
Magnetic-Field Dependence of the Acoustoelectric Effect
Authors: Mikoshiba Nobuo
Published: April 2005

A self-consistent, semiclassical treatment is given for the acoustoelectric effect based on the Cohen-Harrison-Harrison formalism for the ultrasonic attenuation in metals. The calculation is carried out for a simple model in which a sound wave feeds dc crystal momentum into the quasi-free electron system by exerting an oscillating Lorentz force and a deformation-potential force. Emphasis is placed upon the feed back of crystal momentum into the sound wave due to the collision-drag effect and upon the magnetic-field dependence of the acoustoelectric effect. A general relation (the Weinreich formula) between the attenuation of sound and the rate of increase of dc crystal momentum of electrons holds for each interaction of electrons with sound waves. In principle, all characteristic features of the magnetoattenuation of sound such as geometric resonances, cyclotron resonances, etc. can be expected in the acoustoelectric effect. The possibility of this experimental detection is also discussed.
Investigation of Electron Trajectories in an Axially Symmetric Magnetic Field
Authors: Stetson R. F. , Lamborn B. N. A. , Lafferty D. L.
Published: April 2005

The experimental behavior of electron beams of variable energies injected into an axially symmetric magnetic field which varies as 1/r is investigated. When the injection velocity is less than that required for circular motion, the beam spirals in toward an inner radius and reverses direction. The particle orbits are in agreement with those obtained from the equation of motion of a single charged particle injected into such a field.
Interaction of a Bunched Electron Beam with a Gyrotropic Plasma
Authors: Hakki Basil W.
Published: April 2005

The interaction of a prebunched beam with an anisotropic medium is considered for the generation of coherent electromagnetic energy in the low and submillimeter region. Generalized expressions are obtained for the fields created by a prebunched beam of general shape in an anistropic medium. The permeability is assumed to be a scalar constant whereas the permittivity is tensorial. Two special cases are considered: one is that of a helical prebunched beam and the other is that of a rectilinear beam, both interacting with gyrotropic gaseous plasmas. Ionization, scattering, and rf field effects on the beam are neglected.

In addition to the solutions of the inhomogeneous vector wave equation, a method is suggested whereby the free mode solutions could be directly deduced.
Etched Hillocks in BaTiO3
Authors: Stadler H. L.
Published: April 2005

Two kinds of mounds or hillocks have been found on BaTiO3 single crystals after etching. Rounded, flat-topped hillocks were found after etching with 1% HF for 30 sec at room temperature. These hillocks were found where a 180° domain wall had been left for several days and had been removed shortly before etching. Their behavior can be explained by the ad hoc assumption that negative charges are attracted to the 180° domain wall at the crystal surface.

Mounds shaped like Egyptian pyramids were found after etching BaTiO3 single crystals for 30 min in H3PO4 at 155°C. The edges between pyramidal faces always project onto the crystal surface (a 100 plane) in 110 directions.
Angular and Magnitude Dispersion of the Anisotropy in Magnetic Films
Authors: Crowther Thomas S.
Published: April 2005

A physical model for the angular and magnitude dispersion of the anisotropy of magnetic films has been investigated. It is based on the effect of anisotropic strain on a microscopic scale acting on magnetostrictive material. If the strain-induced anisotropy component Hks is less than the intrinsic unstrained value Hko the following results are obtained: (1) Regions with highest and lowest local Hk values are unskewed. Regions with maximum skew have approximately average Hk. (2) Although local skew α and the resultant anisotropy Hk are not uniquely related since each depends on both direction and magnitude of applied stress, their maximum values for a composite film having isotropic strain on a macroscopic scale are related by; αmax=(1/2) arcsin (Hk max−Hko)/Hko.

The following measurements have been taken which tend to support the theory. (1) The angular distribution function has been found to be Gaussian using a measurement technique for which the angle can be read with ±0.1°. (2) The broadening of the Stoner-Wohlfarth switching threshold depends on both angular and magnitude variations. A machine calculation was performed to give this broadening as a function of ασ and Hkσ, the standard deviation of the angular and magnitude distributions, respectively. Using a measured ασ=1.0° the best fit gave Hkσ=0.1 H̄k, which agrees with theory within a factor of three. The data showed that the Hk distribution is not completely symmetric but has approximately 10% of the film with Hk>2Hko.

Measurements of angular dispersion as a function of applied stress for films of known chemical inhomogeneity yield results an order of magnitude below those calculated, using the model described. This is thought to represent the ``stiffening'' effect of magnetostatic and exchange interactions.
Etching of High Purity Zinc
Authors: Brandt R. C. , Adams K. H. , Vreeland T.
Published: April 2005

A method of etching high purity zinc to reveal various etch figures on {101̄0} planes is presented in this paper. Etch figures are formed by polishing in a dichromic acid solution after the introduction of mercury to the crystal surface. No measurable aging time is required to form etch figures at newly formed dislocation sites whem mercury is on the surface prior to deformation. The mercury concentrates at the sites where etch figures form and may be removed by vacuum distillation and chemical polishing before it appreciably affects the purity of the bulk of the crystal.
Theory of Nernst Generators and Refrigerators
Authors: Norwood M. H.
Published: April 2005

Formulas for efficiency and coefficient of performance are derived for devices based on the Nernst and Ettingshausen effects. The equations reduce to those of Harman and Honig in the limits of small figure of merit and refrigerator current, but they do not approach the Carnot limits. To obtain a better device theory, one must solve a two-dimensional partial differential equation in which the current density is allowed to vary with position.

A crude maximization procedure for the figure of merit is shown for a one-band nondegenerate semi-conductor in a weak magnetic field. Experimental data indicate that HgxCd1−x Te alloys are perhaps the best materials for such devices at present.
Defect Structure and Density Decrease in Neutron-Irradiated Quartz
Authors: Weissmann Sigmund , Nakajima Koichi
Published: April 2005

Lattice defects in quartz induced by fast neutron irradiation were studied by combined methods of x-ray diffraction and transmission electron microscopy. The developed defect structure is characterized by clusters of interstitials enriched in ruptured silicon atoms. The size and density of the defect clusters increase with increasing dose until mutual interaction occurs, resulting in the formation of a stable, hexagonal-like structure resistant to prolonged annealing at 500°C. In thin crystals the size and volume fraction of the defect clusters are dependent on crystal orientation, being related to the open screw channels of the quartz structure. A relationship was established between the total volume fraction of defect clusters and fractional decrease in density induced by neutron irradiation, accounting satisfactorily for the hydrostatic density measurements reported in the literature.
Direct Observation of the Oxidation of Aluminum Single-Crystal Surfaces
Authors: Doherty P. E. , Davis R. S.
Published: April 2005

A new technique has been developed by which naturally and anodically formed aluminum oxide produced on single-crystal specimens has been studied in the electron microscope. The low-temperature amorphous oxide grown by the transport of cations was smooth at the metal-oxide interface. However, the oxide-oxygen interface exhibited topography on certain crystal orientations. A high-temperature crystalline oxide was found to grow by the transport of anions. Epitaxial growth was observed on several orientations. The anisotropy of oxide thickness which occurred at elevated temperatures is discussed.

The above results are considered in terms of the structure of the metal-oxide interface.
Interaction of a Conducting Fluid Stream with a Traveling Wave of Magnetic Field of Finite Extension
Authors: Sudan R. N.
Published: April 2005

The ac induction MHD generator with a channel of rectangular cross section and a polyphase winding as a source of the traveling wave of magnetic field of any arbitrary but finite length is treated as a boundary value problem. The solutions obtained indicate that the appropriate parameter that could be treated as a figure of merit for the channel is Γ=4Ω/μσU2, where Ω is the ac frequency, U is the fluid velocity, and μ and σ refer to the fluid with their usual meaning. This parameter is inversely proportional to the magnetic Reynolds number with a characteristic length equal to the distance traveled by the stream in one period of the exciting alternating current. Expressions for the magnetic field, current density, power developed, power output, and Joule losses in the channel are developed as well as their approximations for both large and small Γ. A method to eliminate the electromagnetic end effects due to the finite length of the channel by an appropriate distribution of the exciting current in the polyphase winding is also developed. The feasibility of building fractional wavelength MHD generators then becomes apparent.
Elastic Moduli of Germanium Versus Hydrostatic Pressure at 25.0°C and −195.8°C
Authors: McSkimin H. J. , Andreatch P.
Published: April 2005

Ultrasonic wave velocities and elastic moduli for high purity germanium have been measured as a function of hydrostatic pressure and temperature in the ranges 0 to 30 000 psi and −195.8° to 25°C. The high degree of self-consistency of results provides a further check on the pulse superposition method used. [H. J. Mc-Skimin and P. Andreatch, J. Acoust. Soc. Am. 34, 609 (1962).] The results obtained should prove valuable in increasing the accuracy of third-order elastic moduli determinations.
Particle Size Dependence of Coercivity and Remanence of Single-Domain Particles
Authors: Kneller E. F. , Luborsky F. E.
Published: April 2005

The coercive force and remanence of essentially spherical iron and iron-cobalt alloy particles with diameters from 20 to 3000 Å have been measured at 4°, 76°, and 207°K and compared to the theoretically predicted behavior. The remanence shows a broad, plateau-like maximum while the coercive force has a rather sharp maximum. The maximum of the coercive force occurs at a much larger particle diameter than the maximum of the remanence. It is shown that these essential characteristics follow from the theory. Deviations from theory are seen in the smaller size range and can be accounted for by the distribution of particle sizes. A general treatment of the coercive force of mixtures of thermally stable, high coercive force particles with superparamagnetic and multidomain particles is given.
Response of a Simple Photoconductor to a Square Light Pulse
Authors: Wangsness Roald K.
Published: April 2005

The time dependent signal produced by a finite light pulse of constant intensity is calculated for a photo-conductor for which trapping effects are neglected. It is found that the signal is given by a sum of terms varying exponentially with time and involving an infinite set of time constants whose values are determined by the geometry and the rates of bulk and surface recombination. It is shown that the maximum signal occurs at the end of the pulse and that in order to maximize the ratio of the maximum signal to the noise it is desirable to have equal recombination rates on the two surfaces and to make the ratio of the thickness to the diffusion length as small as is possible without adversely affecting the steady-state detectivity.
Secondary Piezoresistivity in Oxygen Deficient BaTiO3 Single Crystals
Authors: Mattes Brenton L.
Published: April 2005

The anomalous resistive and piezoresistive characteristics of BaTiO3−x ceramics and single crystals are related to domain orientations. It is proposed that an anisotropy in resistivity exists in the different crystallographic directions in the tetragonal phase, reaching a maximum at the tetragonal to orthorhombic transition. A small stress is sufficient to change domain orientations resulting in a large piezoresistive effect (secondary piezoresistivity) because of the anisotropy of resistivity. The change in resistivity was found to be proportional to strain.
Comments on the Eichenbaum-Hernqvist Model of a Low-Pressure Diode
Authors: Mazur P.
Published: April 2005

Using a special model of a collisionless plasma diode, Eichenbaum and Hernqvist have shown the interesting circumstance that two different interelectrode space-potential distributions may exist for the same boundary conditions and the same output voltage and current. It is shown here, using the same boundary conditions, that there are at least several additional and probably an infinite number of possible solutions.
Observation of the Nuclear Resonance in Ferromagnetic Iron to 65 000 Atmospheres
Authors: Litster J. D. , Benedek G. B.
Published: April 2005

Measurements have been made of the pressure dependence of the Fe57 nuclear resonance frequency (v) in ferromagnetic iron to 65 kbars using AgCl as a solid pressure transmitting medium in a belt-type press. v varies linearly with pressure with (∂v/∂P)T=25.5°C= −7.67±0.22 (kc/kbar). Absence of substantial line broadening above 15 kbars indicates that the pressure in our sample was essentially hydrostatic.
Angular-Dependent Sputtering of Copper Single Crystals
Authors: Fluit J. M. , Rol P. K. , Kistemaker J.
Published: April 2005

The dependence of the sputtering yield upon the angle of incidence for copper single crystals by bombardment with 20-keV Ne+, Ar+, and Kr+ ions has been measured. The maxima and minima in this dependence, which have been found, can be correlated to a transparency in different directions of the first few lattice planes. An effective collision diameter deduced from the angular dependence of sputtering by Ar+ ion bombardment on a copper (100) single-crystal surface was found to be 0.39 Å. This value is 3 times larger than the effective collision diameter calculated from the hard sphere approximation for a Bohr potential, taking into account the thermal motion of the lattice particles.
Paraxial Solutions for Accelerated and Decelerated Axially Symmetric Space-Charge Flow
Authors: Borghi R. P. , Dunn D. A.
Published: April 2005

Particle trajectories in the presence of space charge are calculated for prescribed axial potential variations, including linear, parabolic, and sinusoidal variations, using the paraxial-ray equation including space charge for axial symmetry. Solutions are also presented for the potential as a function of distance corresponding to prescribed hyperbolic and parabolic trajectories. The off-axis equipotentials are calculated for some representative cases.

These two-dimensional results are interpreted in the light of one-dimensional space-arge theory in which exact solutions can be obtained for the potential as a function of distance. Some of the limitations of the present theory in which either the potential or the trajectory is prescribed are pointed out.
Developments in the Generation of Electricity and the Production of Soft Magnetic Steel Sheets in Britain
Authors: Wells J. E.
Published: April 2005

The development of the electricity generating industry in Britain, and the production of soft magnetic steel sheets are closely linked. The expansion of both these industries is reviewed, with particular reference to the effect of improvements in generating efficiency and magnetic materials. Some of the difficulties experienced in the manufacture and use of the more advanced magnetic materials are described.

An attempt is made to assess past trends and estimate future requirements for soft magnetic steel sheets and an outline is given of some of the new developments in the generation, conversion, and distribution of electric power. The effect of these developments on the demand for magnetic materials, which is also likely to be affected by the new techniques in steelmaking and processing that are now becoming available, is considered. It is concluded that the total demand for soft magnetic sheets in Britain will have almost doubled by 1972, and that there will be a general reduction in the silicon content of the various magnetic grades at present in use.
Exchange Interactions in Magnetic Compounds
Authors: Smart J. Samuel
Published: April 2005

The basic feature of the Heisenberg-Dirac-Van Vleck model of cooperative magnetic phenomena is the assumption that the interaction Vij between a pair of atoms i and j in a crystal has the form Vij=−2JijSi·Sj,where Jij is an exchange interaction and Si and Sj are spin operators. Such an assumption seems naturally better suited to insulating compounds than to metals and alloys. In principle, it should be possible to determine the Jij for magnetic compounds by comparing experimental data with theoretical predictions based on Eq. (1). In practice, the matter is complicated by the fact that the H-D-VV model is oversimplified, and that even in its oversimplified form exact solutions cannot be obtained for real three-dimensional crystals.

The general problem of evaluating exchange interactions in magnetic compounds from experimental data is reviewed, and specific results are presented for some antiferromagnetic and ferrimagnetic systems where a reasonably good determination of the exchange interactions can be obtained. Some correlations and regularities in the data are noted and discussed. A long review article on this topic is being published elsewhere.
Antiferromagnetic Resonance in Cubic RbMnF3
Authors: Teaney Dale T. , Freiser Marvin J.
Published: April 2005

Antiferromagnetic resonance has been observed in cubic RbMnF3, and the results are in excellent agreement with a theoretical treatment of the resonance conditions. Because a more detailed publication has recently appeared,1 we present in this abstract a brief background and comments on the observed temperature dependence.

Cubic RbMnF3 is characterized by a strong exchange interaction (TN≃54.5°K)2 and low anisotropy. The anisotropy energy has the form EA = K(α4+β4+γ4), where K is positive. When the sublattice magnetization is close to the preferred {111} direction, the anisotropy may be represented by an effective field of 5.0 Oe at 4.2°K. The exchange field is found to be 710 kOe. The exchange and anisotropy fields may be determined separately because the nuclear anisotropy field, HN, may be calculated and the exchange field obtained from 2H EHN = 2HE× (9.43/T).

We are presently investigating the temperature dependence of the resonance field in the helium range. Within the experimental uncertainty of 2%, we find no change in H EHA from 1.4° to 4.2°K. Work is in progress to extend the temperature range and to increase the experimental accuracy.
Antiferromagnetism in fcc and hcp Iron—Manganese Alloys: Mössbauer Effect
Authors: Kimball Clyde , Gerber W. D. , Arrott Anthony
Published: April 2005

That metallic antiferromagnetism can be verified by employing the Mössbauer effect has been demonstrated for fcc FeMn alloys near the compositions of equal atomic fractions and for a hcp Fe-Mn alloy with 17% Mn. The hyperfine fields deduced from measurements of line broadening of incompletely resolved spectra give 33, 39, 43, 42, and 22 kG for 60, 50, 45, and 43% Mn in the fcc phase and 17% Mn in the hcp phase, respectively. The uncertainty is estimated at ±2.5 kG. Néel temperatures of 500°K are found for the four fcc alloys. The hcp alloy has a Néel temperature of 240°K. These values agree with resistivity and susceptibility data. In the light of this treatment of incompletely resolved spectra, a suggested reinterpretation of previous data on antiferromagnetic Cr is offered.
Excitation of Nuclear Magnetic Resonance Modes in Antiferromagnetic KMnF3
Authors: Portis A. M. , Witt G. L. , Heeger A. J.
Published: April 2005

The Mn55 nuclear resonance absorption in KMnF3 has been monitored through the observation of antiferromagnetic resonance at 4.2°K and below. It is found that with increasing rf power a second antiferromagnetic resonance grows at a shifted field position. At 4.2°K a shifted resonance can be observed for driving frequencies between 580 and 680 Mc. As the driving frequency is reduced the position of the shifted resonance moves toward that of the unshifted line. These results are interpreted in terms of the nucleation of regions of the sample with nuclear resonance at the driving frequency. Such regions are present in the absence of excitation as the result of electronic pinning. With rf excitation these regions are expected to grow. The power level at which substantial growth takes place is in good agreement with theory.
Magnetic Character of Very Thin Permalloy Films
Authors: Humphrey F. B.
Published: April 2005

The quasistatic magnetic characteristics of thin Permalloy films have been investigated using a sensitive automatic magnetic torque balance. The most striking feature of the many films investigated in the thickness range below 250 Å is their similarity to thicker films. The data for K are essentially constant until about 80 Å where it drops quickly and smoothly to zero at about 30 Å. The value of the magnetization as a function of thickness supports that of Seavey and Tannenwald, obtained from microwave resonance absorption. The value of the longitudinal coercive force as a function of thickness exhibited a spread of values typical of thicker films of this particular fabrication procedure. Slight dependence on thickness could be observed in general agreement with the data of Behrndt.
Anisotropy Distributions and Unidirectional Hysteresis in Thin Permalloy Films
Authors: Doyle W. D. , Prutton M.
Published: April 2005

The unidirectional rotational hysteresis in a uniaxial Permalloy film has been studied as a function of a rotating steady field and a steady field in the bulk easy direction. Observations were made of both the angular bounds and the magnitude of the unidirectional rotational hysteresis. The results are consistent with a model in which the film is considered as being a uniaxial matrix containing a small volume fraction of regions with randomly oriented anisotropies. The effect of the matrix on the regions is taken as being a field parallel to the magnetization of the matrix.
Ferromagnetic Resonance in Single-Crystal Thin Films of Iron
Authors: Gondō Yasuo , Usami Seiji , Itoh Kunio , Konno Hiroshi , Funatogawa Zenya
Published: April 2005

Oriented (001) iron films deposited on MgO were examined by ferromagnetic resonance at 9.2, 18.4, and 25.0 kMc. A variation of resonance field at 18.4 and 25.0 kMc with an angle θ between the external magnetic field and the [100] direction in the film plane is nearly cos4θ. The crystalline anisotropy constant K1 and the g factor of iron at 300°K are obtained as (4.90±0.10) × 105 ergs/cm3 and 2.01±0.02, respectively. At the lower frequency two resonance peaks are observed only near the 〈110〉 directions. This anomalous effect is explained by a simple single-domain analysis.
Cooling of an Antiferromagnet by Adiabatic Magnetization
Authors: Schelleng J. H. , Friedberg S. A.
Published: April 2005

The heat capacity of powdered MnBr2·4H2O has been measured between 1.4° and 20°K in applied magnetic fields up to 24 kOe. The shift of the Néel point to lower temperatures with increasing field has been observed. A series of adiabatic magnetization measurements from initial temperatures above and below the zero field Néel point (TN(0)=2.13°K) has been carried out. For Ti<TN(0) the anticipated cooling effect is observed for applied fields smaller than that required to make the salt paramagnetic. Adiabatic data have been used to locate the curves of entropy vs temperature computed from the heat capacity relative to the curve for H=0.
Vacancies and Interstitials in Antiferromagnets
Authors: Dreyfus Bernard
Published: April 2005

In this paper static properties of two kinds of point defects in an antiferromagnet are examined. The topology of the two defects, vacancies and interstitials, is different, the first belonging to a well-defined sublattice, and the other acting symmetrically on both sublattices. The perpendicular susceptibility of the vacancy is found to be positive due to a polarization of the medium, overcompensating the lack of magnetization due to the removal of one atomic moment. The additional susceptibility due to the interaction of pairs of vacancies is investigated; its sign depends on whether the two are on the same or different sublattices. It is shown that an interstitial embedded in an antiferromagnetic crystal has a moment that is linked to a plane of easy magnetization, perpendicular to the axis of the crystal, by a pseudoanisotropy field of the order of magnitude of an exchange field. The coupling of such interstitials is shown to decrease as r−7 but could be strong enough to induce cooperative effects.
Dzialoshinski-Moriya Interactions About Defects in Antiferromagnetic and Ferromagnetic Materials
Authors: Arrott Anthony
Published: April 2005

The antisymmetric exchange interaction of Dzialoshinski and Moriya is nonvanishing in the vicinity of lattice defects. In antiferromagnetic materials this can result in a structure-sensitive parasitic ferromagnetism. In ferromagnetic materials there is nonparallel spin alignment which influences magnetization processes. The influence of the Dzialoshinski-Moriya interaction upon the approach to saturation gives magnetic hardness terms and for high density of defects parasitic paramagnetism above apparent saturation. This interaction can be used to treat stabilization of domain wall positions and initial permeability. It should also be important as a loss mechanism in transferring energy from a coherent magnetic mode to incoherent modes. Simple one-dimensional calculations are used for illustration.
Magneto-Optical Readout from a Magnetized Nonspecular Oxide Surface
Authors: Supernowicz E. J.
Published: April 2005

This paper describes a magneto-optical method for obtaining visual display and electronic readout of magnetic information recorded on a nonspecular oxide surface. A recorded oxide surface is placed in contact with a specular ferromagnetic surface, an external magnetic field is applied normal to the two surfaces in contact; and the recorded information is read out by means of the Kerr effect through the back of the specular surface. The method is a useful tool for studying defects in the writing process independently of the reading process in investigations of magnetic recording on oxide surfaces.

It was observed that when the external field was applied, the magnetic pattern was either sharpened or caused to spread, depending on the polarity of the field.
History Effect of Time-Limited Excitation
Authors: Hewitt F. G. , Overn W. M.
Published: April 2005

Electrically alterable switching characteristics have been observed in ferrite memory cores. Abnormal switching characteristics are caused by previous time-limited switching and are not removed by subsequent ``hard'' saturation. The peaking time, peak amplitude, and magnitude of the flux change are all modified. It is proposed that the changes in switching behavior are due to formation of 360° Bloch walls during the combination of time-limited switching and remagnetization to saturation.
Dynamics of Diffusion-Damped Domain Wall Motion
Authors: Janak J. F.
Published: April 2005

The response of 90° and 180° (001)-plane domain walls, acted upon by a damping pressure due to diffusion after-effect, is investigated for steps and ramps of applied field. The resultant motion, using the Néel energy-level scheme for diffusants, is shown to be dynamically stable in the case of the 90° wall, in the sense that the incremental damping coefficient is never negative. Dynamic instability is shown to be possible for the 180° wall, and appears in the step response as a delay between the time of application of the field and the time of an observable response. The ramp response is unstable in a finite sample only when a minimum ramp slope has been exceeded. The ramp response is used to discuss the motion of the 180° wall under triangular-wave drive, and results similar to certain experimental observations are obtained. More publication is planned at a future date.
Study of Permeability Ratios for Use in Nondestructive Readout of Ferrite Memory Devices
Authors: Holzinger Carl S.
Published: April 2005

A study has been made which determines the ultimate one-to-zero ratio which can be realized in the permeability sensing technique of nondestructive readout of binary information from ferrite memory cores. The study is limited to the calculation and measurement of the ratios of incremental permeabilities of various magnetic states for ferrites in which the permeabilities can be attributed to a rotational process. Calculations are based upon a polycrystalline, randomly oriented grain ferrite with a negative anisotropy constant. Each individual magnetic moment is considered to be constrained to an easy axis only by the anisotropy field. Measurements of possible ratios between the permeabilities for the following three conditions are shown to agree within experimental error to those predicted by the calculations.

I. Completely demagnetized sample.

II. Measuring field parallel to the direction of the remanence existing after the application of a saturating field.

III. Measuring field orthogonal to the direction of the remanence existing after the application of a saturating field.

The experimental verifications were arrived at by measurements performed on a long, thin, extruded ferrite tube. It is concluded that the best one-to-zero ratio can be obtained with materials having as high an initial permeability as possible and which still depend upon the rotational mode of operation. The highest-one to-zero ratio then possible is equal to 3.26. Furthermore, this ratio is obtained by using two orthogonal remanence states with the measuring field applied parallel to the remanence which is to represent the binary zero.
Two-Phase Ferrites for High-Speed Switching
Authors: Baba P. D. , Gyorgy E. M. , Schnettler F. J.
Published: April 2005

A plot of the inverse switching time vs the applied field yields three regions of different slope for square-loop ferrites. The low-field region has the lowest slope and is commonly attributed to domain wall motion. As the field is increased, a break in the curve occurs and the slope increases. This intermediate-field portion of the curve has been explained by a nonuniform rotational model, and its projection to the field axis is termed the threshold field H0 for nonuniform rotation. In coincident-current memory operation, twice the coercive force is the maximum drive which can be employed for switching from one remanent state to the other. Therefore, it is desirable to minimize the extent of the domain wall region so that the coercive force will approximate H0 as closely as possible. Then 2Hc will correspond to a higher value of the inverse switching time on the nonuniform rotational portion of the curve, and very fast switching can be attained. Prevalent theories describing domain wall motion in the vicinity of nonmagnetic inclusions indicate that domain wall motion can be impeded by the addition of nonmagnetic second phases of proper size and distribution in a magnetic matrix, resulting in an increase in Hc without affecting H0. A similar approach was used by Nesbitt and Gyorgy on gold-doped Permalloy.

To some extent, the desired effect can be obtained by underfiring the ferrite. However, such firing treatments are difficult to control. A method is described whereby the coercive force is increased while employing a noncritical firing treatment. This has been achieved by the inclusion of palladium as a second phase in a magnesium—manganese ferrite. Particles of the order of 1500 Å were dispersed in the ferrite, and toroidal samples were fired at temperatures between 1250° and 1400°C for firing times up to 12½ h. At 1400°C, within the range of 7½ to 12½ h, variations in Hc were very small. Moreover, in samples containing 10% palladium, Hc increased from 0.9 to 2.7 Oe without changing the Hc of 3.5 Oe. In coincident current operation, the 0, 10, and 20% samples switched in 0.70 0.16, and 0.10 μsec, respectively.
A Study of Rotational Switching
Authors: Iida Shuichi
Published: April 2005

Switching signals by pulsed magnetic fields up to 40 Oe were observed on a single-crystal YIG window frame with legs along <100> directions. A clear magnetic oscillation (∼175 Mc) was found for fields less than about 3 Oe. The amplitude and the damping of the oscillation are enlarged by increasing the drive further, and finally the total remagnetization signal coincides with the initial pulse of the oscillation. Two critical fields Hc2 (7.7 Oe) and Hc3 (20 Oe) were found which correspond to the theoretical minimum critical field for rotational switching for this geometry and to the observed onset of the single-pulse remagnetization, respectively. Switching coefficients of the order of 0.2 μsec Oe and 0.1 μsec Oe are obtained in the regions below and above Hc2, respectively. It is suggested that the nucleation and/or growth of small reversed domains in the early stages of flux reversal may create magnetostatic fields which play an important role in determining the characteristics of these two regions and that it might be better called a noncoherent oscillatory rotational mode.