bluuebunny/crossref_metadata_2025_split huggingface dataset:
Domain Structure Effects in an Anomalous Ferrimagnetic Resonance of Ferrites
Authors: LeCraw R. C. , Spencer E. G. 
Published: April 2005

Measurements of the intrinsic tensor permeability [μ] of unsaturated Ni ferrite at 9300 mc, using cavity perturbation techniques, have revealed an anomalous resonance for negative (anti-Larmor) circularly polarized fields. The resonance has a line width of 70 oe and occurs very near the coercive force which is 13.2 oe. The usual resonance for positive (Larmor) circularly polarized fields occurs at 2750 oe. An interesting consequence of the low-field resonance is that below saturation K″ is negative, where K=K′−iK″ is the off-diagonal component of [μ]. Above saturation K″ is positive. The change in sign of K″ is shown not to violate energy considerations.
These effects are explained by a theory involving rf demagnetizing poles on Bloch walls based on a model with a physically probable domain structure. The theory extends the Polder-Smit mechanism in unmagnetized media to include applied dc fields and circularly polarized rf fields. It is applicable to all ferrites, both mono- and polycrystalline, having domain walls free to move in dc fields of the order of the coercive force. Since the anomalous resonance depends upon the domain structure and appears to occur generally, it is a probe of considerable usefulness for the study of magnetization processes and high-frequency phenomena in ferrites.
Diffraction by an Aperture
Authors: Keller Joseph B. 
Published: April 2005

Diffraction of a wave by an aperture of any shape in a thin screen is treated by a new method—``the geometrical theory of diffraction.'' This is an extension of geometrical optics which accounts for diffraction by introducing new rays called diffracted rays. They are produced when incident rays hit the aperture edge and they satisfy the ``law of diffraction.'' A field is associated with each ray in a quantitative way, by means of the optical principles of phase variation and energy conservation. In addition ``diffraction coefficients'' are introduced to relate the field on a diffracted ray to that on the corresponding incident ray.
By this method a simple formula is obtained for the field diffracted by any aperture. It yields the field in the aperture, the diffraction pattern and the transmission cross section. Explicit formulas and numerical results are given for slits and circular apertures. The accuracy of the results increases as the wavelength decreases, but they are useful for wavelengths even as large as the aperture dimensions.
Effects of Annealing on the Saturation Induction of Ferrites Containing Nickel and/or Copper
Authors: Van Uitert L. G. 
Published: April 2005

The equilibrium distribution of copper between octahedral and tetrahedral sites in the ferrites varies appreciably with temperature. The rate at which these ions approach their equilibrium distribution at a fixed temperature, after quenching from a higher temperature, is much greater for the slightly reduced materials.
Previously unreported deviations from a smooth variation of saturation induction with annealing temperature have been observed in ferrites containing nickel and/or copper that have been prepared to achieve a high degree of homogeneity and hence to be relatively free from defects.
Nonlaminar Flow in Cylindrical Electron Beams
Authors: Harker Kenneth J. 
Published: April 2005

Experimental measurements on the transverse velocity distribution in cylindrically symmetric electron beams emergent from magnetically shielded cathodes are reported. For strong magnetic fields the transverse velocity distribution at the beam center has been found to be composed of discrete classes. These results are explained on the basis of a beam model with nonlaminar flow in which thermal velocities and space charge are neglected. The mechanism depends on the periodic passage of electrons through or very near the beam axis and the fact that the wavelength of this periodicity is a decreasing function of the distance between the point of entry into the magnetic field and the axis.
When the space charge and magnetic forces are comparable, no discrete transverse velocity distribution was observed. It is shown, however, that the beam should still be in the same type of nonlaminar flow as above.
Frequency Spectrum of the Barkhausen Noise
Authors: Biorci G. , Pescetti D. 
Published: April 2005

The spectral density of the Barkhausen noise has been measured and a theoretical interpretation of the results is given. It is assumed that the single pulse is exponential with a time constant of the order of 10−4 second. Then the computed spectral density is constant up to 1 kcps, and then decreases exponentially. This behavior is only slightly dependent on the shape of the pulse. The theoretical conclusions are in good agreement with experimental data taken on iron, nickel, and ferroxcube specimens.
The usual model introduced to explain the mechanism giving rise to the noise leads to the conclusion that the intensity of the spectrum is proportional to the frequency of the magnetizing current. This conclusion is not experimentally verified because of the extreme simplifications involved in the model itself.
Metal Transfer in Sliding Contacts
Authors: Flom D. G. 
Published: April 2005

Transfer of radioactive silver has been studied quantitatively in sliding contacts containing graphite and metal. The rate of transfer from silver-graphite riders to graphite cylinders is initially high but soon approaches a limiting equilibrium state. The amount of silver transfer increases markedly with surface roughness. Further, the transfer is enhanced by the addition of liquid water to the rider track. Back transfer to the rider has been found to consist mostly of loosely clinging dust in the rider face.
Silver transfer to a copper cylinder is much greater than to a graphite cylinder, the difference being roughly twenty-fold. Within the experimental conditions, the transfer/unit time to both graphite and copper cylinders is greater at 1 cm/sec than at 390 cm/sec.
Thermionic and Semiconducting Properties of [Ag]–Cs2O, Ag, Cs
Authors: Davey John E. 
Published: April 2005

Thermionic emission measurements have been carried out on [Ag]–Cs2O, Ag, Cs layers in a state of near maximum thermionic yield. The data have been plotted according to the Fowler equation to determine thermionic work functions; an average value of 0.83 ev has been obtained. However, cooling the layers, below ambient, to temperatures of −40°C, results in an increase of work function of approximately 0.3 ev. Photoelectric emission measurements on these same layers yield an average photoelectric work function of 1.06 ev.
Conductivity measurements on Cs2O, Ag, Cs layers are linear between 100 and −70°C; an activation energy of ∼0.1 ev has been determined from data in this temperature range. Conductivity measurements on Cs2O layers containing no reduced silver exhibit changes in slope similar to the thermionic data. Activation energies computed from above the break in conductivity data are ∼0.25 ev. Cooling the layers to −70°C and below results in increases of activation energy of ∼0.1 ev.
Effect of Elongation on the Electrical Resistivity of Metals. Part I. Aluminum. Part II. Molybdenum
Authors: Peiffer H. R. 
Published: April 2005

The changes in the electrical resistivity of metals at 78°K with elongation are investigated. Part I is devoted to the changes introduced in the face-centered cubic metal aluminum upon elongation at 78°K. Part II discusses the changes that occur in the body-centered cubic metal molybdenum upon elongation at 298°K. Both sections describe the relationship between the portion of the resistivity generally attributed to point defects and the resistivity that remains after the point defect recovery has been completed; these resistivities are proportional to each other for both metals.
It is noted that for both metals the resistivity caused by point defects and the residual resistivity are directly proportional to the elongation. It is further discovered that the rate of resistivity recovery at 145°C for cold-worked molybdenum is directly proportional to the amount of elongation introduced.
Solution to the Equations of Space-Charge Flow by the Method of the Separation of Variables
Authors: Kirstein P. T. , Kino G. S. 
Published: April 2005

The equations for irrotational, electrostatic laminar space-charge flow (no thermal velocities or normal magnetic field at the cathode) are set up in terms of the action function. The resulting nonlinear partial differential equation is first reduced, by the method of the separation of variables in cylindrical polar coordinates, to the solution of a set of first-order, nonlinear, ordinary differential equations in one coordinate. It is shown that it is possible to predict axially symmetric, electrostatic, hollow beams from the inside of hollow cylindrical cathodes with space-charge-limited emission which asymptote, theoretically, to other extremely thin cylinders—though thermal velocities would, in practice, limit such a convergence. The characteristics of a particular beam, and the electrode system to produce it are shown.
The beams which result from the separation of variables in other coordinate systems are described. In spherical polar coordinates one obtains hollow axially symmetric beams from a conical cathode, which may asymptote to other cones; in a less familiar coordinate system, spiral coordinates, sheet beams from equiangular spiral cathodes result.
Finally, it is shown how the method may be extended to include magnetic fields transverse to the cathode. Some new solutions to space-charge flow in crossed electric and magnetic fields from a space-charge-limited cathode are mentioned.
Optical Theory of Thermal Velocity Effects in Cylindrical Electron Beams
Authors: Herrmann Gabriel 
Published: April 2005

Most previous treatments of long high-density electron beams have assumed laminar flow. Recent experiments show that in many cases this assumption is unjustified. The present theory is based on a non-laminar optical model which treats thermal velocities as an integral part of the motion. A Maxwellian distribution of initial transverse velocities is assumed at the cathode, and a first-order focusing theory is applied in order to calculate trajectories at any point in the beam. It is shown that whenever a long beam is confined by a focusing field, images of the cathode are formed repeatedly along the axis.
When applied to uniform magnetic focusing fields, the theory predicts the periodic formation along the axis of cathode images and crossovers, and a relative rotation of successive images. Such effects have been reported. Values of required focusing fields are derived for given space-charge and thermal-velocity conditions, and relations are established between beam spread and transverse velocities. The resulting picture differs radically from the laminar model of beam flow.
Method for Measuring Magnetostriction Corrected for Initial Domain Distribution and its Application to Nickel and Iron
Authors: Stauss H. E. 
Published: April 2005

A method has been developed for the measurement of magnetostrictive strain that overcomes the effect of initial domain distribution in isotropic materials. A cubic specimen is used, placed between two iron rods of the same cross section. The combination is put along the common axis of two like solenoids connected in series. Strain is measured with a resistance strain gauge, once parallel to the magnetic field, and a second time normal to the field after the specimen has been rotated 90°. At saturation the algebraic difference gives 3/2 of the saturation magnetostriction. Use of the difference eliminates or reduces a number of experimental errors in addition to that arising from nonrandomness of initial domain distribution.
The method has been applied to grade A nickel and armco iron.
Rotational Model of Flux Reversal in Square Loop Soft Ferromagnets
Authors: Gyorgy E. M. 
Published: April 2005

The present paper analyzes a rotational model of flux reversal in ferromagnetic materials. A brief review of the experimentally established details of the flux reversal process in square loop ferrites is given. The discrepancies between the experimental results and the predictions of the domain wall motion theory are discussed. The switching coefficient, Sw, is examined in detail.
The rotation model is based on the solution of the modified Landau and Lifshitz equation, but does not assume that the magnetization rotates uniformly throughout the sample. The model predicts the shape of the output voltage pulse, the relationship between the flux reversal time and the applied field, and the minimum switching coefficient that can be obtained for a given ferrite. The switching coefficients determined experimentally for ferrites, permalloy tape, and thin evaporated metal films (with zero transverse field) are within a factor of three of the minimum value of Sw predicted by this model.
Magnetic Measurements on Some Precipitating Systems
Authors: Berkowitz A. E. , Flanders P. J. 
Published: April 2005

In the systems Au–Ni and β-brass-Fe, ferromagnetic precipitate particles develop in a nonmagnetic matrix. Single crystal samples of these alloys have been examined by measuring saturation magnetization, torque curves, rotational hysteresis, and remanence.
The data on the Au–Ni system have been analyzed to infer particle anisotropy distributions, orientation of the ``easy'' axes of the particles, and other features of the precipitate particle system. Electron micrographs of the precipitate particles are in general agreement with this analysis. The measurements on the β-brass-Fe system indicated that the precipitate particles were single crystals with the same crystal habit as the matrix, and were elongated in the 〈111〉 directions. The temperature dependence of the torque curves was identified with the temperature dependence of shape and magnetocrystalline anisotropy.
Precipitation and Magnetic Annealing in a Copper-Cobalt Alloy
Authors: Becker J. J. 
Published: April 2005

In an alloy containing 2% cobalt, balance copper, it is possible to quench a nonmagnetic solid solution from 1000°C and then produce a ferromagnetic precipitate in a nonmagnetic matrix by aging at several hundred degrees. The magnetic properties of this precipitate can be correlated with the size and shape of the precipitate particles. Considerable information about the precipitation process can be obtained in this way. In these experiments, saturation magnetization, torque, rotational hysteresis, remanence, coercive force for zero magnetization, and coercive force for zero remanence (which behaves in a surprising fashion) have been observed during the course of aging. In particular, the effect of a field during aging in producing magnetic anisotropy (``magnetic annealing'') has been studied and is shown to occur entirely during the growth of the particles, after the precipitation is complete.
The precipitation process is viewed as one in which the particles as they grow are first superparamagnetic, then stable single domains, and finally multidomain. This point of view is consistent with all of the varied phenomena observed.
Effects of Composition and Processing Variables on the Magnetic Properties of the 50% Nickel-Iron Alloy
Authors: Savitski M. J. 
Published: April 2005

In a factorial experiment, a study has been made of the effects of small amounts of alloying elements and processing variables on the magnetic properties of the 50% nickel-iron alloy. The composition variables were: three levels of manganese, two of silicon, two of sulfur, and two of oxygen. The processing variables were: hot rolling at two temperature levels, annealing or not annealing after hot rolling, and final annealing at six temperature levels. The ingots were processed to tape from which toroidal cores were made.
The results of magnetic tests made with a constant current, flux-reset core tester indicate that certain elements need to be added to the melt to produce a grain-oriented alloy with satisfactory magnetic properties, and that the processing must be compatible with the additions made. The binary manganese-oxygen addition was most beneficial. In general, hot rolling at a high temperature level was beneficial, and annealing after hot rolling was detrimental to the magnetic performance.
Orientation Study of Ultra-Thin Molybdenum Permalloy Tape
Authors: Koh P. K. 
Published: April 2005

Quantitative pole density stereograms of {111}, {220}, {200}, and {113} poles of ⅛-mil molybdenum permalloy tape were developed in order to establish its cold rolled deformation texture and annealed textures.
Cold rolled the tape induced multiple slip common to all face-centered-cubic metals and developed (110) [3̄35] and (110) [33̄5] end orientations which deviate 5° about [110] from the recognized {110} 〈112〉 brass deformation texture.
On annealing at 771°C the cold rolled tape was found to develop (120) [001]+(210) [001] and (113) [7̄8̄5] +(113) [785̄] orientations as components of the annealed texture which bear in general at 35°-45° rotation orientation relationship about 〈111〉 with the cold rolled end orientations.
Annealing at 1160°C developed the same texture as that obtained after 771°C annealing.
From the pole figures made on 927°C annealed tape, the same annealed texture prevailed whether the pole figure was made on its full ⅛ mil thickness or on its central 0.00005 in. section.
Hysteresis loop tracings made on the cold rolled tape revealed an apparent direction of easy magnetization along the rolling direction. No easy magnetization direction was revealed in the rolling plane on the annealed tapes. These findings support the deductions from the corresponding pole figures.
Ionic Valences in Manganese-Iron Spinels
Authors: Eschenfelder Andrew H. 
Published: April 2005

Because both manganese and iron assume multiple valences in oxide structures, it is possible to fabricate spinels over a continuous range of composition from Mn3O4 to Fe3O4. Magnetic-moment data for samples fabricated within this range are reported and an interpretation of the data in terms of the distribution of ions of manganese and iron is presented.
The data agree with previous indications that manganese ferrite, MnFe2O4, is an almost completely normal spinel with Mn2+ on A sites and Fe3+ on B sites. In addition, the usual assumption that excess iron replaces manganese as Fe2+ on B sites is substantiated. However, the data are not compatible with the previously held assumption that Fe3+ is replaced by excess manganese as Mn3+. Instead, the variation of magnetic moments and Curie temperatures with composition is interpreted in terms of a model in which excess manganese replaces Fe3+ as Mn4+ and an equal amount of iron is converted to Fe2+. When the manganese content gets so high that all the iron is Fe2+ (Mn2FeO4), manganese then replaces the iron as Mn3+ and reconverts an equal amount of Mn4+ to Mn3+, and the Mn3+, because of its tetragonal nature, introduces spinel twinning.
It is proposed that the Mn4+–Fe2+ pair in octahedral coordination is stabilized with respect to a Mn3+–Fe3+ pair because of the interaction of the manganese orbitals with the 2p orbitals of the surrounding oxygen anions.
Model for Nonlinear Flux Reversals of Square-Loop Polycrystalline Magnetic Cores
Authors: Haynes M. K. 
Published: April 2005

The theory of the reversal wave forms of polycrystalline magnetic cores proposed by Goodenough is based on the growth of ellipsoidal domains of reverse magnetization which originate from nucleating centers at grain boundaries. The present model extends this theory with the assumption that the nucleating centers are randomly distributed throughout the core volume. Radial field variations are neglected.
The rate of change of reversed magnetization area of the irreversibly moving and colliding walls is calculated as a function of their position, starting from a Poisson distribution of nucleating centers, and then converted to a function of flux. The equation derived for rate of flux change is dxdt=4.82Sw(H−H0)(1−x)(−ln1−x2)23,where Sw is the switching coefficient, H0 is the threshold field, H is the applied field, and x is the ratio of flux density to retentivity.
This nonlinear differential equation is solved for the simple case of constant current drive. For more complicated circuit conditions, solutions of the core equations require numerical methods. Programs have been written for the IBM Type 704 DPM to calculate the behavior of circuits containing many such cores interacting and switching together. Results obtained check reasonably well with experimental evidence.
New Concept in Large-Size Memory Arrays—the Twistor
Authors: Bobeck Andrew H. 
Published: April 2005

Three methods have been developed for storing information in a coincident-current manner on magnetic wire. The resulting memory cells have been collectively named the ``twistor''. Two of these methods utilize the strain sensitivity of magnetic materials and are based on the century old Wertheim or Wiedemann effects; the third utilizes the favorable geometry of a wire.
The effect of an applied torsion on a magnetic wire is to shift the preferred direction of magnetization into a helical path inclined at an angle of 45° with respect to the axis. The coincidence of a circular and a longitudinal magnetic field inserts information into this wire in the form of a polarized helical magnetization. In addition, the magnetic wire itself may be used as a sensing means with resultant favorable increase in available signal since the lines of flux wrap the magnetic wire many times.
An experimental transistor-driven 320 bit twistor array has been built. The possibility of applying weaving techniques to future arrays makes the twistor approach appear economically attractive.
New Magnetic Core Loss Comparator
Authors: Tompkins R. E. , Stauffer L. H. , Kaplan A. 
Published: April 2005

A new method has been developed for the rapid measurement of magnetic flux density and power loss in single sheet steel specimens. In use the sheet specimen is inserted into an exciting unit which generates an ac magnetomotive force to provide the required flux density. A measuring head is then pressed against the surface of the specimen and the power loss and flux density are read directly on an indicating instrument. Localized measurements in areas as small as 1 sq in. are possible.
Simultaneous pickup of the emf induced in the specimen by the time varying flux, and the mmf generated by the exciting unit is accomplished by a pair of probes and a modified Chattock coil. Specially designed amplifiers, integrating circuits and switching arrangements enable the operator to observe the hysteresis loop or to read the power loss directly. Specimens of varying shapes and sizes may be employed without cutting or stacking and power loss distributions are readily observed.
Some Observations on Creep in Zinc Single Crystals
Authors: Stüwe H. P. 
Published: April 2005

A concentrated load, applied to the surface of a Zn single crystal, produces a hexagonal dimple if this surface is parallel to the basal plane of the crystal lattice. The rim of these dimples is formed by six sets of edge dislocations moving into the six slip directions with increasing loading time, thus causing the dimple to grow. The dimple contours can be photographed with a microfocus x-ray tube. Measurements of a large number of dimples showed:
(1) For a given loading time, dimple size increases linearly with the applied load.
(2) For a given load, dimple size increases with loading time until the shear stress at the dimple rim has been lowered to a value characteristic for the material used, below which creep velocity is either zero or extremely low.
(3) This critical shear stress is independent of temperature.
(4) It depends on the impurity concentration of the crystal in the way predicted by the model of Cottrell.