bluuebunny/crossref_metadata_2025 huggingface dataset:
Current Noise in Pyrolyzed Polyacrylonitrile
Authors: Brophy James J.
Published: April 2005

Current noise measurements of the organic semiconductor polyacrylonitrile pyrolyzed in nitrogen at temperatures from 550° to 900°C reveal conductivity fluctuations similar to those attributed to carrier fluctuations in inorganic semiconductors. The current noise spectra exhibit characteristic time constants of 10−2, 3×10−4, and 5×10−5 sec which are independent of pyrolysis temperature and are tentatively associated with the molecular structure leading to conductivity. The observed noise magnitude suggests the existence of a large number of independent sub-volumes which increase in size with treatment temperature. Samples pyrolyzed above 700°C exhibit 1/f noise that may be indicative of a different molecular structure.
Base Region Transport Characteristics of a Diffused Transistor
Authors: Kennedy David P. , Murley Philip C.
Published: April 2005

A one-dimensional analysis is given on the minority carrier transport characteristics of a transistor base region containing an arbitrary drift field distribution. This field is assumed to enhance—or retard—the motion of minority carriers between an emitter and collector junction, thereby modifying the influence of bulk recombination mechanisms. Base region transport efficiency is established in terms of the transistor current gain when an ideal emitter junction is assumed. Applications of this analysis are demonstrated by establishing the base region transport efficiency for diffused transistors. Two types of structures have been analytically investigated: the alloy-diffused transistor, containing a diffused collector junction and an alloy-type emitter; and the double-diffused transistor constructed entirely by diffusion techniques. For practical semiconductor devices, a comparison of these two structures has shown negligible differences in their base region transport efficiency and, furthermore, the drift mechanisms within these diffused devices have little influence upon their one-dimensional current gain.
Light Pulse from Halogen-Quenched GM Counter Discharges
Authors: Davis W. P. , Worthington W. C.
Published: April 2005

The light pulses associated with the halogen-quenched Geiger-Müller discharge of three commercially available end-window counters have been observed with a photomultiplier. Two of the counters were geometrically identical and filled to approximately the same pressure with neon and argon, respectively. The third tube was physically larger and contained neon. An individual light pulse, the duration of which is very much shorter than the corresponding normal voltage pulse, has a reproducible and distinctive shape. The amplitude of the light pulse and reciprocal of its risetime increase approximately linearly with increasing overvoltage. Arguments are given that relate the rise time to the velocity of propagation of the discharge. The smaller of the two neon tubes displayed double pulses over its entire Geiger region while the other tubes seemed entirely free of this phenomenon.
Temperature Dependent Luminescence of CaWO4 and CdWO4
Authors: Beard G. B. , Kelly W. H. , Mallory M. L.
Published: April 2005

The relative efficiencies and decay times of alpha particle induced scintillations of CaWO4 and CdWO4 were investigated as a function of temperature in the range 10° to 375°K. Their behavior at intermediate and high temperatures is in agreement with that expected from the Mott-Seitz-Kröger configurational coordinate model. Values of EQ, thermal quenching energy, of 0.34 and 0.31 ev were found for CaWO4 and CdWO4, respectively. As the temperature was decreased below 60°K, an increase in the decay times and a decrease in the relative efficiencies were found. This behavior can be explained qualitatively by assuming the existence of a trapping level.
Effect of Elastic Strain on the Superconducting Critical Temperature of Evaporated Tin Films
Authors: Blumberg R. H. , Seraphim D. P.
Published: April 2005

The superconducting critical temperature of a large number of tin films on soda lime glass substrates are reported. The critical temperatures depend upon the stress arising in the films when they are constrained to follow the contraction of the glass on cooling to liquid helium temperature. It is shown that the crystalline orientation of the films is significant in determining the magnitude of the stress and the variation in critical temperature relative to bulk tin. For films with the tetrad axis in the plane, the stresses along that axis at helium temperature can reach 4.5×103 atm and the critical temperature may increase by 0.23°K. For both diad axes in the plane, the stress and the change in critical temperature is much less. The piezoresistivity constants along the tetrad and diad axes of single crystals were measured, π33 = 9.8±0.5ρ3×10−6/atm, π11 = −7.0±0.6ρ1×10−6/atm. The temperature dependent part of the resistivity of films at 77°K is increased above the values of bulk metal in accordance with a piezoresistive effect. For films much thinner than 300A, the critical temperature is observed to increase with decreasing thickness. For these thin films the constraint of thermal contraction imposed by the substrate appears to be insufficient to provide the entire increase in critical temperature.
Plastic Bending of InSb
Authors: Duga J. J.
Published: April 2005

Plastic bending of InSb is found to result in changes in the electrical properties which are similar to those found in other semiconductors. The total carrier concentration is decreased by the trapping of charge carriers on dislocation acceptor levels and the electron mobility is reduced for conduction perpendicular to the axis of bend. The mobility parallel to the axis of bend is unaltered, suggesting that the space-charge cylinders associated with edge-type dislocations are smooth, although the dislocations themselves are thought to be zig-zagged. Although the electrical properties are in qualitative agreement with Read's theory, it is shown that large disagreements can occur in heavily-deformed impure specimens. The theory is extended to the case where scattering by ionized impurities is appreciable. A method is also proposed whereby one may determine the dislocation density from the magnetic-field dependence of the Hall coefficient. The density so determined is in good agreement with that found from etch-pit counting and from Nye's relation.
Magnetic Shielding by Superconducting Films
Authors: Oakes R. J.
Published: April 2005

The magnetic field distribution and supercurrent density are calculated exactly by means of the Maxwell-London equations for the case of an ideal superconducting spherical shell immersed in a steady uniform magnetic field. It is shown that the magnetic field is strongly attenuated by the spherical shell even if the shell thickness is as small as 1000 A.
Energy Mismatch and Cutoff Waves in a Two-Dimensional Space-Charge Flow
Authors: Rowe J. E. , Lee R. Y.
Published: April 2005

A general treatment of the input boundary value problem for two-dimensional space-charge flow is developed using a theory of electrostatics (Thomson's) which notes that in an electrostatic problem the electric field distribution is such that the electrostatic-field energy is a minimum. This principle is used to determine the average energy density mismatch and the starting conditions for finite thickness beams in M-type backward-wave oscillators. It is shown that the mismatch is greatest for strong space-charge fields, high-circuit attenuation, and signal frequencies below the cyclotron frequency. The starting length and beam velocity are greater as calculated by the variational procedure than obtained by the approximate method. Under certain conditions the average energy density mismatch is greater than 20% of the electrostatic field energy in the absence of the beam.
Space-Charge-Limited Currents in Organic Crystals
Authors: Mark Peter , Helfrich Wolfgang
Published: April 2005

Electrical conductivity measurements were performed with thin (50 μ) single crystals of p-terphenyl, p-quaterphenyl, and anthracene supplied with aqueous electrodes, one of which was an iodine-iodide solution (acceptor electrode), and the other an iodide solution. The results strongly indicate that the acceptor electrode can form ohmic contact for hole injection into these crystals and that space-charge-limited currents can be drawn through them. The crystals were found to contain hole-trapping states the location-in-energy of which can be approximated by a decreasing exponential distribution above the valence band. The measurements showed that the hole mobility in p-terphenyl is about 3×10−2 cm2/v sec, is independent of the field at least up to about 4×104 v/cm, and that the hole-trap concentration is at least 1013 cm−3. The acceptor electrode used does not form ohmic contact to crystals of naphthalene and diphenyl; an explanation for this is proposed. Some theoretical aspects of ohmic contact formation to organic crystals and space-charge-limited current flow in insulators are also discussed.
Pulsed Probe Measurements
Authors: Bills D. G. , Holt R. B. , McClure B. T.
Published: April 2005

A pulsed probe has been used to measure certain parameters of a time varying plasma in mercury vapor. Langmuir probe characteristics have been obtained by pulsing the probe voltage to successively higher values for μsec intervals at specific times relative to a repetitive discharge pulse. Curves showing the time dependence of the plasma potential, electron temperature, and electron density relative to this pulse are presented. The probe characteristics do not exhibit a sharp break at the plasma potential. This is related to a disturbance of the plasma by the probe. A novel and precise technique for determining the actual plasma potential is described. This technique depends upon the abrupt appearance of a spike on the leading edge of the probe current pulse.
Spectroscopic Measurements of Temperatures and Densities in a Cesium Plasma
Authors: Donohue Robert J. , Majkowski Richard F.
Published: April 2005

The ion, electron and atom number densities, and electron temperatures of a cesium plasma generated in a diode have been measured by spectroscopic techniques. The theoretical bases for these techniques are outlined. The errors involved in applying these theories to heavy atom collision-dominated plasmas are discussed. Working equations for the electron, ion and atom temperatures, and number densities are developed. Among the working equations developed and applied are those for the determination of the electron number density from the continuum intensity and Stark broadening. Temperatures in the cesium plasma were 0.7 ev with ion and electron number densities of the order of 1015 cm−3. The agreement of cesium pressure computed from the spectroscopically determined temperatures and number densities and that from vapor pressure curves strongly suggest the existence of thermal equilibrium. The agreement in the values of electron number densities determined from continuum intensity and Stark broadening measurements justify the approximations made in applying these theories to the cesium plasma.
A Solution to the Frenkel-Kontorova Dislocation Model
Authors: Hobart R. , Celli V.
Published: April 2005

An exact solution to the nonlinear difference equation which describes a static configuration in the Frenkel-Kontorova dislocation model is given. The solution is in terms of a power series which is proved convergent. Previously, only approximate solutions had been obtained by replacing the difference equation by a differential equation. A numerical comparison is made between the exact and the approximate solutions and the Peierls energies they give.
Electrical Conduction Mechanism in Ultrathin, Evaporated Metal Films
Authors: Neugebauer C. A. , Webb M. B.
Published: April 2005

The electrical conduction mechanism in the film plane of ultrathin, evaporated metal films was investigated. These films consist of a planar array of many small discrete islands. The conduction process consists of, first, charge carrier creation which is thermally activated and involves charge transfer between initially neutral particles, and, second, the drift velocity of these charges in an applied field. Charge transfer between particles occurs by tunneling. The following features were predicted and can be verified experimentally: the conductivity depends exponentially on reciprocal temperature, and it should be independent of field at low fields. Deviations from the exponential temperature dependence can be understood in terms of a spectrum of activation energies, while deviations from Ohm's law at high fields can be explained readily in terms of a field dependent activation energy.
Progress in Field-Emission Work-Function Measurements of Atomically Perfect Crystal Planes
Authors: Young Russell D. , Müller Erwin W.
Published: April 2005

The field electron microscope has been used previously to measure the work function of thermally smoothed single-crystal tungsten planes. In this work the field ion microscope is used to create atomically perfect single-crystal planes by field evaporation and then to observe and preserve these clean surfaces. The slope of the field emission Fowler-Nordheim plot then gives the ratio of the three halves power of the work function to the field. Two techniques have been developed in order to obtain a second relationship between work function and field: (1) temperature dependence of field-emission current density and (2) energy distribution of field-emitted electrons. While investigating temperature dependence it was found that a reinterpretation of the Gel'berg et al. data for the work function temperature dependence of molybdenum up to 1100°K revealed the following unexpected cubic temperature dependence: φT=φ0+0.44×10−10T3 ev.
Field Emission Cathodes
Authors: Van Oostrom A.
Published: April 2005

The vacuum requirements to obtain stable field emission cathodes are discussed. To keep the average work function of a tungsten emitter constant, the total pressure of all chemically active gases should not exceed 10−14 Torr. To minimize ion bombardment of the emitter surface the helium pressure should be reduced by ion pumping even with tubes made of an alumino-silicate glass. The relationship between the current density and the slope of a Fowler-Nordheim plot has been calculated. Experimental evidence is given that variations in the work function can be compensated by changes in the field strength in such a way that stable field emitters are obtained. A qualitative explanation of such a mechanism is suggested.
On the Small Signal Power Theorem of Electron Beams
Authors: Bobroff D. L. , Haus H. A. , Klüver J. W.
Published: April 2005

The small signal power theorem for electron beams is reviewed in the light of recent controversies on the subject. The physical significance of the theorem is explained and its role as a mathematical identity is discussed. The assumptions and the boundary conditions of the linearized theory are carefully stated. The small signal power theorem is rederived in a simplified way. New examples and applications are treated.
Preparation and Properties of Mercury-Doped Germanium
Authors: Borrello S. R. , Levinstein H.
Published: April 2005

Mercury-doped germanium has been prepared by a modified zone leveling technique. Mercury as an impurity produces p-type germanium with two energy levels. Hall measurements yield values of 0.087 and 0.23 eV for the lower and upper levels, respectively. Activation energies determined from the long wave-length threshold of the photoconductive response are in good agreement with these values.
Relaxations in Copolymers of Tetrafluoroethylene and Hexafluoropropylene
Authors: Eby R. K. , Wilson F. C.
Published: April 2005

The modulus and internal friction of copolymers of tetrafluoroethylene and hexafluoropropylene (HFP) were measured with longitudinal waves at a frequency of 12 Mc between −80° and 260°C. The dielectric dissipation factor was measured at 0.1, 1.0, 10, and 100 kc between −180° and 200°C. Samples included copolymers with compositions ranging from pure polytetrafluoroethylene to pure polyhexafluoropropylene. A relaxation at −10°C (12 Mc) in polytetrafluoroethylene shifts to higher temperatures with increasing HFP content. Data suggest that 5 to 13 main-chain carbon atoms are involved, a size consistent with assigning the relaxation to motions of a small point defect in the crystal lattice. Molecular models indicate that the effects of these defects are reduced by perfluoromethyl groups which enter the lattice as another kind of point defect. Dielectric and mechanical relaxation temperatures agree approximately and yield the same activation parameters. These parameters exhibit no significant variation with HFP content and follow a relation which applies to activated processes in inorganic solids. The relation also obtains for a relaxation at 197°C (12 Mc) in polytetrafluoroethylene. This relaxation shifts to lower temperatures and the activation enthalpy decreases with increasing HFP content. Dielectric data do not exhibit the relaxation, and heating polytetrafluoroethylene near the melting point does not introduce sufficient polar groups to alter this result. Another relaxation observed below −150°C in the dielectric but not in the ultrasonic data is independent of polymer density and HFP content.
Checkerboard Domain Pattern of Single-Crystal Thin Iron Film
Authors: Sato H. , Astrue R. W.
Published: April 2005

Basic domain structures of epitaxially grown single-crystal thin films of iron are investigated by the powder pattern technique. For films with (001) orientation, where two easy axes of magnetization lie within the plane of the film, a checkerboard pattern, i.e., a regular square domain pattern made up of 90° walls only, is expected to appear, since 90° walls should predominate over 180° walls in thin films. In the asevaporated condition, however, the film possesses a fairly complicated domain structure and the checkerboard pattern is obtained only after alternating-field demagnetization. It is thus clearly indicated, in thin films, that there exists a lack of demagnetizing energy necessary for the formation of closure domains and that an external force is necessary to reach the demagnetized state with a closure domain structure.
Possibility of Subgrain Rotation during Recrystallization
Authors: Li James C. M.
Published: April 2005

The possibility of the rotation of a subgrain with respect to its neighbors as a natural process during recrystallization is analyzed thermodynamically and kinetically. It is found that it is energetically possible if the direction of rotation favors the elimination of low-angle boundaries over that of high-angle boundaries, the elimination of twist and asymmetric boundaries over that of the tilt and symmetric boundaries, and the elimination of the large-area boundaries over that of the small-area boundaries. Since the rotation direction has two degrees of freedom, there exists a relation between the two degrees of freedom such that directions whose two degrees of freedom fulfill such a relation provide no driving force for rotation. All other directions will supply free energy to rotate in one sense or the opposite. Kinetically one of the following two processes within one boundary can be rate-controlling: the cooperative movement of dislocations in the boundary, and the cooperative diffusion of vacancies in the lattice. The rotation of a subgrain favors the elimination of one of the boundaries which contributes the largest fraction of driving force and also the largest fraction of resistance. This causes the subgrain to coalesce with the other subgrain separated by this boundary. The estimated time required for one such coalescence compares favorably with the observed rate of subgrain growth in Al.
Resistance of a High-Intensity Arc
Authors: Hart Philip J.
Published: April 2005

A simple method, utilizing a noninductive connection, is described for the direct measurement of the resistive component of the potential drop across a semi-enclosed arc. By this method the resistance, power dissipation, and efficiency are determined for an arc due to a capacitor discharge having a peak current of about 2.5×105 A. The minimum resistivity is found to be 1.5×10−3 Ω cm, a value lower than values reported previously. A current curve is analyzed to determine resistance of the entire circuit. Inductance interrelation are considered further.
Sputtering of Dielectrics by High-Frequency Fields
Authors: Anderson G. S. , Mayer Wm. N. , Wehner G. K.
Published: April 2005

A novel method for sputtering insulators in the plasma of a low-pressure discharge is described. The method utilizes rf fields whereby the positive charge accumulation at the target surface, resulting from positive ion bombardment, is periodically neutralized during each cycle. The method has many useful applications for cleaning, etching, and sputtering of insulators, as well as for removing deposits from observation windows.
Energy Gaps of the III–V and the (Rare Earth)-V Semiconductors
Authors: Sclar N.
Published: April 2005

A simple empirical analysis allowing the prediction of the energy gaps of the III–V semiconductors and the rare-earth nitride, phosphide, and arsenide semiconductors is given. The analysis is based on a correlation of the semiconductor energy gaps with the ionic and covalent atomic radii of the constituent elements and is not sensitive to changes in crystal structure in going from one compound to the other. Excellent agreement is obtained between the predicted and existing experimental values. Certain of the predictions are at variance with previously predicted values and the need for experimental work to decide between the alternative treatments is indicated.
Circuit Theory of Coupled Transmission Systems
Authors: Kino G. S. , Paik S. F.
Published: April 2005

A method of obtaining an exact circuit equivalence of a class of coupled transmission systems from Maxwell's equations is described. The solution for the propagating characteristics of the coupled transmission system can be readily obtained from the circuit analog. The process of reducing field equations to circuit equations is carried out for a particular coupled structure, a coupled helix system. The circuit theory yields frequencies of the coupled modes as functions of the propagation constant, rather than the propagation constant in terms of frequency. The circuit theory has the great advantage that it is as valid for strongly coupled systems as it is for weakly coupled systems. The usefulness of the approach is demonstrated by applying the theory to several slightly different propagating systems.

Expressions for the energy and the power flow derived from the circuit theory are compared to the true power flow and the energy in the transmission system. It is shown that the energy of the system in the equivalent transmission line corresponds to the true energy, if the circuit is assumed to propagate slow waves. The power flow relation obtained from the circuit analog differs from the true power flow by the factor of (vp/vg) which is attributed to the dispersive nature of the circuit. Important relationships between impedances of the transmission system defined in various ways are obtained from the power flow relation.
Space-Charge-Limited Currents in Single-Crystal Sillcon Carbide
Authors: Ozarow V. , Hysell R. E.
Published: April 2005

Non-ohmic behavior of the current voltage characteristic was noted on high-resistivity silicon carbide crystals with fused tungsten contacts. In order to explain the shapes and magnitudes of these characteristics the theory of two-carrier space-charge-limited currents was employed. Calculations with this treatment gave a common electron and hole lifetime of ∼5×10−5 sec, a recombination cross section of ∼4×1019 cm2, and a current enhancement factor of ∼103.
Scattering of a Plane Wave by an Inhomogeneous Sphere under the Born Approximation
Authors: Albini F. A.
Published: April 2005

The scattering of an electromagnetic wave by an inhomogeneous, spherically-symmetrical region of space characterized by a complex ``dielectric constant'' near that of the surrounding medium is solved under the Born approximation. It is shown by direct comparison to the exact results of G. Mie in the case of the homogeneous sphere that polarization and scattering cross sections are predicted satisfactorily for ``small spheres'' which are nearly transparent. Wave amplitudes in the far zone, as well as scattering and absorption cross sections, are presented in terms of integrals over the inhomogeneous zone.
Diffusion in Cobalt-Nickel Alloys
Authors: Hirano Ken-ichi , Agarwala R. P. , Averbach B. L. , Cohen Morris
Published: April 2005

The self-diffusivities of Co60 and Ni63 in cobalt-nickel solid solutions exhibit a greater activation energy below the Curie temperature (Tc) than above. Values of ΔQ=Q (ferromagnetic) —Q (paramagnetic) are approximately equal to RTc. This is interpreted to indicate that the increment in activation energy arises from an increase in the formation energy of a vacancy in the ferromagnetic lattice, with the additional binding energy arising from the interaction of a spin with the Weiss field.
Calcium Tungstate: Czochralski Growth, Perfection, and Substitution
Authors: Nassau K. , Broyer A. M.
Published: April 2005

The conditions for the Czochralski growth of calcium tungstate to give crystals of quality suitable for continuous optical maser operation at room temperature are described.

Purity, growth direction, and perfection considerations are discussed. Optical examination in polarized light, the presence of gas bubbles, solid inclusions and Tyndal scattering haze, and interferometer measurements provide estimates of the degree of imperfection present.

Transition and rare-earth metal ion additions were studied, and data on distribution coefficients, valency, and charge compensation are given.

Among miscellaneous data measured are the thermal expansion coefficients in the a- and c-axis directions up to 1030°C, and redeterminations of the solubility and optical transmission curve.
Stacking Fault Energy in Silicon
Authors: Aerts E. , Delavignette P. , Siems R. , Amelinckx S.
Published: April 2005

In hexagonal networks in the (111) plane of silicon both families of nodes are ``extended.'' This implies that intrinsic as well as extrinsic stacking faults have small energy. The two stacking fault energies are ∼50 ergs/cm2 and ∼60 ergs/cm2. It is not possible at present to decide which energy belongs to which stacking fault.

Both the etch pits, and the dislocations on which they are centered, can be revealed in the electron microscope.
Spherical Langmuir Probe in ``Drifting'' and ``Accelerated'' Maxwellian Distribution
Authors: Medicus G.
Published: April 2005

The treatment in a preceding paper of the ``accelerated half-Maxwellian'' (AM), essentially according to Langmuir's probe theory for spherical probes, is supplemented by that of the Maxwellian with superimposed drift (DM). The differences between the two cases can be characterized in the following way. (a) Energy spectra: In the DM at least an infinitesimal number of carriers which happen to fly exactly against the drift have zero energy, whereas in the AM there are no carriers with energies smaller than corresponding to acceleration voltage. The energy spectrum in the AM, therefore, is zero between zero and acceleration energy, with an abrupt rise at the latter energy. The energy spectrum in the DM is zero only at zero energy, with a smooth rise to a maximum. (b) Ions: In the AM, carriers of opposite sign are accelerated in opposite direction and the acceleration energies are proportional to the charges of the carriers, whereas the drift energy in the DM is proportional to the masses of the carriers, which all drift in the same direction. Therefore the ion probe current in the DM at large enough drift velocities is as significant as the electron probe current, whereas in the AM the ion probe current retains its secondary role which is essentially determined by (me/mi)½, me=electron mass, mi=ion mass. The second derivatives of the probe currents with respect to the probe voltage show most clearly the significant differences between the two cases. Typical examples are plotted.
R
2 Line Optical Maser Action in Ruby
Authors: McClung F. J. , Schwarz S. E. , Meyers F. J.
Published: April 2005

Optical maser action at the R2 line in ruby has been observed. Because of a fast thermal relaxation between the two 2E levels, it is not usually possible to satisfy the maser conditions at the R2 line when stimulated emission is occurring at the R1 line. However, if maser action can be suppressed at the R1 line, even at high inversion, it can be made to occur at the R2 line by the appropriate selection of operating conditions. This has been accomplished by using, for end reflectors, multilayer dielectric interference filters which have high transmission at the R1 line and low transmission at the R2 line. The selection of the operating conditions requires a correction of the absorption coefficients for the R1 and R2 lines based on the Boltzmann distribution between the two excited states. When the Boltzmann correction is made, the calculations show reasonable requirements on pumping threshold and reflectivities.
All-Magnetic Logic Elements Using Strained Permalloy Wire
Authors: Irons H. R.
Published: April 2005

An element for performing digital logic which employs Permalloy wire, solenoids, and resistors and utilizes a two-phase current pulse source has been studied experimentally. The reentrant hysteresis loop exhibited by a torsionally strained Permalloy wire provides the mechanism for power gain. A balanced input circuit assures unidirectional information flow and provides means for obtaining logic functions. Each element consists of two 0.6-in. bifilar-wound solenoids for bias and reset pulse currents, one or several 0.025-in. solenoids to which logic inputs are applied, an output resistor and a Permalloy wire core. The application of a bias current pulse to the logic element will cause the magnetization to change from the zero to the one state provided a signal is present simultaneously at the input to nucleate the magnetization reversal. The reset current pulse switches the magnetization back again and produces an output across the bias coil which is used to control one or several following elements. A buffer zone, the magnetization of which is controlled by the reset pulse, separates adjacent logic elements to minimize element interaction. Measurements on elements employing a 1.5-mil, 5–79 Permalloy core show that a switching time of 15 μsec and a power gain of 10 can be achieved. Preliminary tests indicate satisfactory operation over the temperature range of −55° to +185°C. These elements have been used to construct flip-flops, binary counters and a serial adder which employs majority logic. The circuits operated successfully when the pulse currents from the power supply were varied by ±20%. Because an open flux structure is used, it is believed that similar techniques will have application in circuits employing deposited magnetic films.
Anisotropy Sources for Electrodeposited Permalloy Films
Authors: Lauriente M. , Bagrowski J.
Published: April 2005

Experimental evidence has been found to indicate that electro-deposited iron-nickel films are sensitive to the geometric anisotropy of the chain-like growth of crystallites that compose the conducting film of the substrate. Chromium-gold films were vacuum evaporated on glass slides at normal and oblique incidence. Fired gold films were also made to be used as examples of minimum geometric anisotropy. Using Wolf's solution as an electrolyte, Permalloy films were electrodeposited, some with an some without a magnetic field. Uniaxial anisotropy was found for all the specimens, including the controls, with the exception of those specimens plated without a magnetic field on both, normal incidence substrates, and fired gold substrates. Angles as small as 2° were found sufficient to induce a marked anisotropy. From the knowledge that evaporation at oblique incidence creates a geometric anisotropy by a process of self-shadowing of the crystallites, it is believed that this geometric anisotropy is replicated in the magnetic film as a shape anisotropy which in turn induces a magnetic anisotropy. In support of this theory, directional polishing of the substrates was also found to induce an anisotropy, although in these cases usually with higher HK values. The epitaxy model can be helpful for applying data from evaporating techniques to plating techniques. Magnetic films in this study averaged 3000 A in thickness. The B—H tests were made at 400 cps. Conclusions are that, in this experiment, the anisotropy induced by the magnetic field can be separate from the one induced by the substrate, and sensitivity to geometric anisotropy is pronounced.
A Theoretical Model for Partial Rotation
Authors: Thomas H.
Published: April 2005

A simple model which consists of a set of parallel strips with different anisotropy constants, interacting by the magnetic stray field, is investigated. It displays an incoherent reversal process similar to the partial rotation process observed in thin Permalloy films, and shows under certain conditions a unidirectional rotational hysteresis.
Magnetic Structure Work at the Nuclear Center of Grenoble
Authors: Bertaut E. F. , Delapalme A. , Forrat F. , Roult G. , De Bergevin F. , Pauthenet R.
Published: April 2005

Three structures are briefly reported: FeRh is antiferromagnetic at low temperatures and ferromagnetic above 60°C. Fe has in both region a high moment of about 3μB; Rh has a definite moment in the ferromagnetic region of about 0.6μB. Cr3Se4, a nonstoichiometric compound with ordered holes, has a magnetic structure closely related to that of MnBr2. UCoO4 isomorphous of UMgO4 (space group Imma) is antiferromagnetic with Co–O–O–Co interactions and a Néel temperature of 12°K.
Temperature Dependence of the Magnetocrystalline Anisotropy of Face-Centered Cubic Cobalt
Authors: Rodbell D. S.
Published: April 2005

Single crystals of face-centered cubic cobalt have been examined between 4.2° and 850°K. The usual transformation to the hexagonal structure below 700°K is avoided by using two special forms of samples: (a) thin films evaporated onto MgO substrates, and (b) the precipitated cobalt-rich phase in a 2% Co–Cu single crystal. In both cases the fcc cobalt is stabilized by and has a close correspondence with the host lattice. Standard ferromagnetic (electron-spin) resonance techniques have been used to determine the magnetocrystalline anisotropy parameters K1/M and K2/M over the temperature range indicated, and, in addition, the spectroscopic splitting factor g is found to be 2.06±0.03 independent of temperature. The temperature dependence of the anisotropy constants is in accord with the relation K(T)/K(o) = [M(T)/M(o)]n, where for M(T)/M(o) we have taken the determination by V. Jaccarino [Bull. Am. Phys. Soc. 4, 461 (1959)] of the temperature dependence of the cobalt-nuclear magnetic resonance frequency which we assume to be proportional to the magnetization. The results that are obtained indicate that the power n of the dependence noted is nearly 10 for K1 and much higher for K2. At 0°K samples of type (a) have — K1/M = 600 oe.
Appearance of a Weak Ferromagnetism in Fine Particles of Antiferromagnetic Materials
Authors: Schuele W. J. , Deetscreek V. D.
Published: April 2005

Several experiments have been carried out on NiO which may be interpreted as confirmation of the suggestion of Néel that antiferromagnetic material in fine particle form should exhibit a weak ferromagnetism and superparamagnetism. The initial susceptibility of the nickel oxide between 22 A and > 1000 A increases with decreasing particle size. The susceptibility decreases with decrease in temperature below room temperature for all but the smallest size sample. This sample had a very large susceptibility and an ``S''-shaped magnetization curve, characteristic of superparamagnetic material. In the intermediate size range, cooling through the Néel temperature in a field introduces an additional magnetization which is field independent.
Magnetic Transitions in Cubic Spinels
Authors: Menyuk N. , Wold A. , Rogers D. , Dwight K.
Published: April 2005

Magnetization curves of the cubic spinels MnCr2O4, CoCr2O4, MnV2O4, and CoV2O4 have been obtained between 4.2°K and their Curie points. With the possible exception of MnV2O4, all the curves indicate the presence of a magnetic transition within this temperature range. Although all these materials have been reported to be normal spinels, inconsistencies between our results and the recent theory of spin configurations in normal cubic spinels led to further experiments which established that CoV2O4 is not, in general, normal.

Theory suggests the presence of two types of transition in MnCr2O4 and CoCr2O4, but only one has been observed in each case. The temperatures at which the observed break in the magnetization curves of these materials occurs can be interpreted by ascribing them to different types of transitions. The interpretation of the MnCr2O4 magnetization curve is compatible with the neutron diffraction results of Corliss and Hastings.
Electrodeposition of Magnetic Materials
Authors: Wolf I. W.
Published: April 2005

A discussion of the electrodeposition of alloys of the Ni-Fe-Co system is presented. Solutions from which these metals are deposited are described and the role of their constituents discussed. The various applications for these deposited materials is reviewed pointing out their advantages and shortcomings. A detailed description of the electrodeposited thin film is given.
Pyromagnetic Test of Spin Wave Theory in Metallic Nickel
Authors: Pugh Emerson W. , Argyle Bernell E.
Published: April 2005

The temperature dependence of the spontaneous magnetization of metallic nickel has been studied between 4.2° and 120°K by a pyromagnetic technique developed by the authors. Fractional changes in magnetization as small as a few parts per million could be detected near 4.2°K. The resultant data were fitted by the method of least squares to a theoretical equation containing terms descriptive of thermal excitation of spin waves in the presence of an effective magnetic field plus a T2 term descriptive of collective electron behavior. The best fit of the data to this equation is obtained using the spin wave terms alone, provided an intrinsic energy gap is assumed in the spin wave dispersion law of 2.7°K for magnetization parallel to the [111] axis and 1.9°K parallel to the [100] axis. Enhancement of this gap by an externally applied field follows theoretical predictions. It is noted that the measured difference between the gap temperature along the two principal axes has the value theoretically predicted from previous measurements of magnetic anisotropy energy, however the isotropic contribution observed in this experiment has not been theoretically anticipated. A possible origin for the isotropic gap is proposed in terms of interaction of polarized s and d electrons. It is also pointed out, however, that the ``isotropic effective field'' may be a spurious result, originating in thermal expansion effects not included in the theoretical equation to which the data were fitted. Finally, a new type of pyromagnetic measurement is described which can be used to determine the temperature dependence of the magnetic anisotropy.
X-Ray and Magnetic Studies of CrO2 Single Crystals
Authors: Cloud W. H. , Schreiber D. S. , Babcock K. R.
Published: April 2005

The oxygen parameter of CrO2, which has the rutile structure, has been determined to be u=0.301±0.004. Single-crystal measurements of cell constants over the temperature range −200° to +200°C show the unusual decrease in the c axis with increasing temperature in agreement with x-ray powder results reported by other workers. An estimate of the magnetocrystalline anisotropy has been obtained from measured magnetization curves of a small single-crystal sphere of CrO2. The directions of easy magnetization lie in (100) planes at an angle of approximately 40° to the tetragonal axis.
Some Superparamagnetic Properties of Fine Particle δFeOOH
Authors: Simpson A. W.
Published: April 2005

Various samples of δFeOOH have been prepared all with substantially the same particle shape and size but with differing low-temperature saturation magnetizations. The particles were found to be hexagonal platelets with a mean diameter of 200 A and a thickness of 30 A. The magnetization of the samples was varied by varying the preparation conditions and also by partially decomposing the material to αFeOOH and αFe2O3. It has been shown that at a little above room temperature the powders were all superparamagnetic and that the variations of magnetization with preparation conditions qualitatively support a model proposed by Francombe and Rooksby. The variation of the Blocking temperature of a particular preparation as its magnetization was reduced by successive decomposition is also discussed. The results are tentatively interpreted in terms of a constant term corresponding to the normal anisotropy energy and a variable one due to the Lorentz internal field.
Two Effects of Changes in Tension
Authors: Yamada Osamu
Published: April 2005

In the Rayleigh region of the initial magnetization, increasing or decreasing of a tension leads to an irreversible increase in magnetization. This phenomenon can be attributed to two effects, namely the first and the second effect. For the first effect, the magnitude of the change of magnetization is directly proportional to the value of magnetization itself and is also directly proportional to the change of tension but independent of the sign of the tension change. For the second effect, the change of magnetization is also directly proportional to the value of magnetization but is not proportional to the change in tension. The second effect has, in general, a different value for increase and decrease of tension and is accompanied by the appearance of un-symmetrical hysteresis loops. The first effect is caused by the displacement of 180° walls, in contrast to the second effect which is associated with 90° walls.
Anisotropy in Rolled Permalloy Tape
Authors: Gyorgy E. M. , Treves D.
Published: April 2005

The anisotropy induced in gold-doped Permalloy by cold rolling and subsequent heat treatments has been investigated using a recording torque magnetometer. The material was cold rolled from 0.014 in. to 0.000125 in. and then heat treated for 2 hr in a dry hydrogen atmosphere. The torque curves obtained could be decomposed into a hard and soft component. For fields below 200 oe, the torque curves due to the hard component have a tangent-like shape with the peak a few degrees from the hard direction, while the torque curves due to the soft component have the regular shape corresponding to uniaxial magnetocrystalline anisotropy. Both components are uniaxial with the easy direction along the roll direction.

The hard component is independent of the heat treatments up to about 900°C and has an equivalent anisotropy field of the order of several hundred oersteds. The high apparent anisotropy of the hard component and its independence of the heat treatment suggest that this component arises from a magnetostatic effect. By etching the tape it has been shown that the hard component is due to the surface structure of the tape. The surface structure is probably the result of the rolling process.

The soft component is strongly dependent upon the heat treatment subsequent to the cold work and almost vanishes at an annealing temperature of about 650°C. This decrease is consistent with the ordered pair mechanism suggested by Chikazumi. The small residual soft component at high annealing temperatures is very sensitive to the rate of quenching. This behavior may indicate the presence of partial ordering and some degree of crystal orientation. The value of the anisotropy field due to the soft component is approximately equal to the measured value of the threshold for rapid rotational flux reversal.
Small Angle X-Ray Scattering from MnS in Silicon Steels
Authors: Banerjee Bani R. , Lenhart R. E. , Robinson W. H.
Published: April 2005

In silicon steels, a dispersed MnS impurity phase is believed to pin grain boundaries, inhibit grain growth, and permit the desired secondary recrystallization for optimum orientation, grain size, and magnetic properties of the finished material. However, no experimental evidence has yet been obtained to establish the size distribution of this impurity phase. Therefore, the size distribution of such a precipitate was explored by a small-angle x-ray scattering technique, with a spectrometer using a Johansson-focusing monochromator; spurious surface effects were carefully avoided. Laboratory heats of 3.2% silicon steel compositions with varying sulfur, were prepared by vacuum induction melting of high-purity components; these materials were carefully processed to 0.0005-in. thick foils. Using a sulfur-free sample as reference standard for residual surface scattering, a plot of ln τ (2θ) vs (2θ)2 showed the presumed MnS particles to be 20 A to 150 A in diameter. These results agreed with preliminary observations by transmission-electron microscopy.
Magnetic Anisotropy of the Demagnetized State
Authors: Barbier Jean-Claude , Ferlin-Guion Bernadette
Published: April 2005

An isotropic polycrystalline substance, demagnetized in a slowly decreasing alternating field, is in general magnetically anisotropic. The magnetization curve J(H) in a given direction will depend on the angle between H and the direction of demagnetization. We have compared the two magnetization curves for φ=0 and φ=π/2. Their difference is a maximum for a field of 0.75 Hc, and can be more than 60% of J. This effect does not exist in substances with uniaxial magnetic anisotropy like hexagonal Co, or in samples with large internal stresses. We have also investigated the variation of the anisotropy of the demagnetized state of a sample which was made progressively more uniaxial by an increasing stress. Furthermore, if a complete demagnetization is followed by a partial demagnetization in the perpendicular direction, this partial demagnetization only modifies the initial state if a certain critical field is exceeded. We have determined some characteristics of this critical field.
Grain-Size Effects in Oriented 48% Nickel-Iron Cores at 400 Cycles
Authors: Littmann M. F. , Harris E. S. , Ward C. E.
Published: April 2005

The constant-current, flux-reset test at 400 cycles has been used widely to evaluate core material for magnetic amplifier applications. An important criterion by this test is the ``gain'' or ratio of flux change to change in dc control magnetizing force. It is well known that gain is related to the squareness ratio Br/Bm of the hysteresis loop.

This study shows that gain is also very sensitive to the grain structure as well as the crystal orientation of the core material. Material having a homogeneous structure has high gain, whereas if partial secondary grain growth has occurred, resulting in a large difference in grain size for the material, the gain can be reduced by a factor 1.5 to 3 times. The effect was artificially simulated by combining two cores of different grain size. Individually, the cores had high gain but together they had very low gain. The cause is ascribed to the difference in coercive force between the large and small grains. The conclusion is reached that high gain is obtainable from material consisting entirely of either large or small grains of proper crystal orientation.