bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Results of an Electron Microscopical Study of the Metallographic Structure of Two Alloys for Permanent Magnets (Ticonal G and Ticonal X)
Authors: De Jong J. J. , Smeets J. M. G. , Haanstra H. B. 
Published: April 2005

The microstructures of Ticonal G and Ticonal X in the condition of optimum magnetic properties are studied by the electron microscope using the direct carbon replica. It is argued that a very critical and extensive checking of results is essential in order to arrive at reliable conclusions. Work along these lines demonstrates that: (a) The main structural patterns for Ticonal G and X are the same; (b) the details of the structure of Ticonal G and X differ strikingly with respect to texture, width, length-to-width ratio, delineation and intergrowth; and (c) the influence of the magnetic field during cooling on the structure of Ticonal G on a plane ∥Hu can be shown directly.
It cannot yet be decided whether the structure in the optimum condition is a true two-phase structure or a single-phase structure with periodic fluctuations in composition.
It is possible that the dimensions revealed by etching do not represent those of the magnetic areas.
Relation between Colloid Pattern and Permanent Magnet Precipitate during the Magnetization Reversal in Alnico V
Authors: Kronenberg K. J. , Tenzer R. K. 
Published: April 2005

Improved electron microscope observation technique has confirmed some of the basic assumptions on the structure of Alnico V and has added knowledge of details. The permanent magnet precipitate was investigated at various states of its growth starting from nucleation. Pictures with details smaller than 20 A reveal the completely developed structure of Alnico V which differs somewhat from former descriptions. It can be recognized clearly that the precipitated particles have grown together to a continuous anisotropic network subdividing the matrix.
Colloid patterns on these surfaces have been observed with electron microscope. During the reversal of magnetization, an anisotropic structure in the colloid-covered areas of the pattern can be distinguished. The colloid particles align themselves, preferring one of the two faces of the precipitated structure. This is most pronounced in the steep part of the demagnetization curve. It can be observed as soon as the colloid starts to form patterns.
The necessary surveying of magnet surfaces was possible by preparing very thin oxide replicas with a simple technique that eliminated the former ``floating'' method. Replicas were stripped from the surface which preserved the orientation without destroying the surface of the magnet.
Magnetic Determination of Shape Distribution of Single Domain Powders
Authors: Johnson Clark E. , Brown William Fuller 
Published: April 2005

By demagnetizing a magnetic powder specimen with diminishing alternating fields of various initial amplitudes and by interpreting the results with the Stoner-Wohlfarth model, one can obtain information about the shape distribution of the particles. We have done this with powders of acicular γ-ferric oxide at various temperatures; the temperature variation of the results gives information about the size distribution. The sample is first magnetized to saturation; the diminishing ac field is then applied and the remanence measured.
Since the particles are not aligned along the applied field, it is necessary to get the equivalent magnetization curve for an aligned sample by operating on the data mathematically. The results indicate that only a small volume fraction of the γ-ferric oxide particles are small enough to be a paramagnetic. There is a relatively large volume fraction of particles with nearly zero critical field. We believe this is caused by particles which change their magnetization by a mechanism different from the Stoner-Wohlfarth uniform rotation.
On a volume basis, the shape distribution curves peak at a length-to-diameter ratio of about 1.6:1, which gives a coercive force of 300 oersteds. The coercive force agrees very well with measured values. The length-to-diameter ratio does not agree with electron microscopic observations, which give a mean of about 5:1.
Magnetic Properties of Cube Textured Silicon-Iron Magnetic Sheet
Authors: Walter J. L. , Hibbard W. R. , Fiedler H. C. , Grenoble H. E. , Pry R. H. , Frischmann P. G. 
Published: April 2005

Cube textured magnetic sheet containing approximately 3% silicon in iron has been developed in the General Electric Company Research Laboratory. The magnitude of the cube texture as determined by torque magnetometer tests is of the order of 90% or greater when compared to a single crystal with a (100) [001] orientation. The magnitude of the texture was confirmed by x-ray diffraction pole figures.
Static dc magnetic tests and 60 cycle ac w loss tests made on single strip samples taken both parallel to the rolling direction and at right angles to the rolling direction indicate nearly equal magnetic properties in both directions of the sheet. These properties are equivalent to the magnetic properties measured in the single good direction of the ``grain oriented'' transformer material. Finally, two transformers were made: one using laminations of the cube textured silicon iron, the other of the ``grain oriented'' material. It was found that transformer made of the cube textured material produced significantly lower energy losses at all inductions and at 17 000 gauss the losses were approximately 60% of the losses produced by the ``grain oriented'' transformer. Similarly the current required to produce 17 000 gauss in the cube textured transformer was again about half that required to excite the ``grain oriented'' transformer to the same induction.
Effect of Hydrostatic Pressure and Temperature on the Magnetic Properties of a Nickel-Zinc Ferrite
Authors: Adams C. Q. , Davis C. M. 
Published: April 2005

Magnetic properties of a nickel-zinc ferrite (15% NiO, 35% ZnO, 50% Fe2O3) were measured over a temperature range of 23°C to 110°C at hydrostatic pressures up to 40 000 psi.
The relation between the shift in Curie temperature, ΔTc, and the change in pressure, Δp, was empirically found to be ΔTc=0.078(Δp)0.316.
It is shown that if magnetic anisotropy and internal strains limit the magnetizing processes, the relation between coercive force, Hc, maximum flux density, Bm, and initial permeability, μ0, is given by Hc=δBm/μ0,
where δ is a proportionality constant. The experimental results obtained over the entire range of temperature and pressure verify the above relation. The value of δ is 2.56 for the ferrite investigated.
Growth of Magnetic Garnet Crystals
Authors: Nielsen J. W. 
Published: April 2005

Single crystals of magnetic garnets have been grown from solutions of molten lead oxied, iron oxide, and the oxides of yttrium, samarium, erbium, or gadolinium. The crystals are grown by slowly cooling melts from 1325°C to near 900°C. A convenient composition is 52.5 mole % PbO, 44 mole % Fe2O3, and 3.5 mole % M2O3 where M is Y, Gd, Er, or Sm. Crystals of yttrium-iron garnet have been grown which contain gallium partially substituted for iron.
The method may also be extended to the growth of nonmagnetic yttrium gallium garnets by using a melt which is 72.7 mole % PbO, 26 mole % Ga2O3 and 1.3 mole % Y2O3.
Bismuth oxide can be used as a solvent for the growth of magnetic garnet crystals but the substitution of bismuth in the garnet lattice makes it less desirable than lead oxide.
Miniaturized Resonant Antenna Using Ferrites
Authors: Grimes D. M. 
Published: April 2005

The radiation resistance and reactance of point source dipoles are profoundly affected by the surrounding medium. A radiator of length l in an infinite ferrite medium is electrically μl meters long if μ=ε (relative permeability and permittivity).
For very small ferrite spheres, the radiation resistance is determined by the relative permittivity, the effective reactance length by both the permittivity and the permeability. Thus it is possible to exchange length for resistance. Further work on linear radiators surrounded by ferrite in the form of a prolate figure of revolution is indicated.
Spin-Lattice Relaxation Time in Yttrium Iron Garnet
Authors: Farrar R. T. 
Published: April 2005

The spin-lattice relaxation time in yttrium iron garnet (YIG) has been measured by a pulsed ferromagnetic resonance method similar to that of Bloembergen and Wang and Damon, in which the z component of magnetization is directly observed.
A microwave pulse with 2×10−8 sec rise and decay time, 5×10−7 sec long, and 2 w peak power is applied to a TE102 rectangular cavity operating at 9300 mc sec. The z component of magnetization Mz changes at the beginning and at the end of the rf pulse. The time of decay of the changing Mz signal at the trailing edge of the pulse (at which time the applied rf field is zero) is a measure of the spin-lattice relaxation time.
A spherical sample of YIG, 0.03 in. diam, is placed in a quartz tube, 0.05 in. o.d., about which a five turn coil of No. 38 wire is wound. The coil with sample is inserted in the center of the cavity with the axis of the coil in the z direction. At this position, the rf magnetic field is maximum and the electric field is a minimum. The presence of the coil does not measurably change the properties of the cavity. The voltage induced in the coil is proportional to the change in Mz and is observed on a high speed oscilloscope. The time constant of the equipment is approximately that of the exciting pulse. Thus the spin-lattice relaxation time can be accurately determined directly if it is appreciably larger than this value.
The ferromagnetic resonance line width is 2.3 oersteds and the measured spin-lattice relaxation time is 7×10−8 sec. Discussion is given relating these measurements to those reported in the accompanying papers.
Temperature Dependence of Ferromagnetic Anisotropy
Authors: Carr W. J. 
Published: April 2005

The temperature dependence of the crystalline anisotropy constants of iron, cobalt, and nickel is discussed.
It is shown that Zener's result for iron (i.e., the first anisotropy constant varies as the tenth power of the magnetization) also may be derived from molecular field theory.
In cobalt a satisfactory agreement with experiment is obtained by using Zener's results together with the postulate that the intrinsic anisotropy varies with thermal expansion in the manner recently calculated by the author.
For nickel also the temperature dependence of K1 seems to require, in addition to the tenth power of the magnetization, a multiplicative factor that is linear in the temperature. No explanation has been found for this latter term.
Theory of Magnetostriction and g Factor in Ferrites
Authors: Tsuya Noboru 
Published: April 2005

A quantum mechanical theory based upon the Heitler-London approximation has been developed to explain the spatial variation of magnetostriction and g factor in ferrites. As a first step, the electronic wave functions of cations of transition elements in the crystal field were found, taking into account the crystal structure of ferrites. The g factors of various cations in ferrites were determined by a method similar to that of Abragam and Pryce, and g factors thus found were related to those of ferrimagnetic resonance absorption by the use of the theory of Wangsness and the author.
The magnetostriction was obtained by the perturbation method and it was concluded that there are four mechanisms predominant among those giving rise to magnetostriction. They are (1) the interplay of spin-orbit interaction with the strain potential, (2) classical dipolar interaction, (3) the interplay of anisotropic exchange interaction with the strain potential, and (4) the interplay of the potential with the intra-spin-spin interaction. Other mechanisms were estimated to be ineffective. The predominant mechanisms in Ni ferrite are (1) and (2); in Co ferrite, (1); in magnetite, (1), (2), and (4). In annealed Mn ferrite and Cu ferrite, the mechanism (2) is most effective. In quenched Cu ferrite, both mechanisms (2) and (3) are the most important.
Effect of Cobalt on the Relaxation Frequency of Nickel-Zinc Ferrite
Authors: Schnettler F. J. , Monforte F. R. 
Published: April 2005

The complex permeabilities of a number of Ni–Zn–Co ferrites were measured as a function of frequency from 0.1 to 250 mc/sec. These ferrites were prepared under identical conditions from reagent grade chemicals. Their compositions differed in the relative amounts of cobalt, nickel, and zinc they contained, the amount of iron being held constant. A number of specimens of each composition were prepared at different firing temperatures, so as to include a variation in the degree of reaction.
An analysis of the data was made in which the initial permeability and relaxation frequency were correlated with certain composition and structure variables. They include the quantity of cobalt, the nickel-zinc ratio, the firing temperature, and the amount of shrinkage which occurred during firing. It was found that these variables would account for 88% of the variations of the initial permeability and 70% of the variations of the relaxation frequency. A further result of the analysis defines the conditions for obtaining maximum quality (μ0f0) at a given value of initial permeability.
Pulse Generator Based on High Shock Demagnetization of Ferromagnetic Material
Authors: Kulterman R. W. , Neilson F. W. , Benedick W. B. 
Published: April 2005

The shock wave from a pellet of high explosive is passed without attenuation through one leg of a closed ferromagnetic core which has been previously magnetized. The shock wave demagnetizes the core, reducing the flux from the remanent value to zero. This change in flux generates a voltage in any winding wound on the core. Idealized calculations indicate that the voltage pulse generated in this manner will be a squarewave with amplitude, in volts, given by eg = NBRvw, and a pulse width, in seconds, given by T = s/v, where N is the number of turns, BR the remanent magnetization (webers/m2) and v is the shock velocity (m/sec). It is also assumed that the core has a rectangular cross section, w being the width of the core (m) in the direction perpendicular to BR and v, and s being the thickness of the core (m) in the direction parallel to v.
Experimental tests have produced output pulses with an amplitude of 6400 v/turn-meter of w where the length of the pulse was in fair agreement with the known shock velocity of the material used. At the present time it is believed that the operation of the device can be explained by a transducer mechanism which converts some of the energy of the shock wave into electrical energy.
Transitions from Ferromagnetism to Antiferromagnetism in Iron Aluminum Alloys
Authors: Sato H. , Arrott A. 
Published: April 2005

From a study of magnetic isotherms over the range of compositions from pure Fe to 40 atomic percent Al in Fe and over temperatures from 4°K to 300°K, we have produced strong evidence for the existence of super-exchange interactions between iron atoms separated by aluminum atoms. The iron rich alloys show ferromagnetism in the usual way, but, for concentrations approaching 40 atomic percent Al, the alloys behave as antiferromagnetic with Néel points near liquid hydrogen temperatures. There is a transition range of composition in which the stable state just below the Curie temperature is ferromagnetic but at low temperatures is antiferromagnetic.
The large changes in magnetic properties occur for the ordered structures and in composition ranges where the number of nearest neighbor iron-iron interactions is changing rapidly with composition, but where the number of next nearest neighbor iron-iron interactions remains practically constant. These considerations lead to a model where only the nearest neighbor direct positive exchange interactions between iron atoms, and indirect negative exchange interactions between iron atoms separated by an aluminum atom are taken into account. The treatment by a Bragg-Williams type calculation leads to a qualitative understanding of the observed magnetic effects in the iron aluminum system, including the differences between the disordered state and the two types of ordered states. The model also leads to a reinterpretation of neutron diffraction data.
Surface Motions of a Thick Plate
Authors: Knopoff L. 
Published: April 2005

The motion of a thick elastic plate, infinite in two dimensions and bounded by air on the two parallel faces, has been studied. The plate is excited at a point on one face, as in Lamb's problem, by a force impulsive in time, and directed normal to the surface. The early motions of this surface have been described by Lamb. An exact solution, in closed form, for the motion of the opposite face is available only at the epicenter. The motions at all other points are evaluated by a seismic model. At the epicenter, the measurements and the calculations are in agreement; at this point a strong P pulse and a weaker S pulse are observed. This S phase has a wave form, for short pulses, which is the time integral of the wave form of the P phase. Off the axis of symmetry, the form of the S pulse is the same as that of the P pulse. The S pulse becomes quite strong away from the epicenter, attaining an amplitude of nearly four times that of the P pulse at about 45° in the Solenhofen limestone plate. A bodily S-surface P phase, whose existence is in agreement with predictions based upon geometrical arguments is discerned at angles exceeding the critical angle.
A simplified description of the early motion of the reverse face may be constructed. This simplified response is a useful tool which may be used to reduce the complexity of the calculations encountered in other boundary value problems.
Fast Neutron Attenuation in Graphite
Authors: Duggal V. P. , Puri S. M. 
Published: April 2005

Spatial distribution of a fast neutron flux has been measured experimentally in graphite (density 1.62 g/cc) using threshold radioactivants. For these measurements neutrons were obtained from D-T and D-Be reactions. Assuming the neutron flux to vary as 1/R2e−R/L, the values of relaxation length L (between 50 cm and 70 cm) obtained with a phosphorous detector from D-T and D-Be neutrons are 23.5±1.5 cm and 19.7±1.0 cm, respectively. It is also seen that fast flux falls off less rapidly than resonance neutron (1.46 ev) flux after about 50 cm in graphite.
The spatial distribution of neutrons between the energies 1 Mev to 3 Mev from a plane monoenergetic source of 3-Mev neutrons has also been obtained using a Monte-Carlo calculation.
Statistics and Time Dependence of Mechanical Breakdown in Fibers
Authors: Coleman Bernard D. 
Published: April 2005

A new phenomenological approach to quantitative discussions of the statistics and time dependence of mechanical breakdown is presented. The theory permits the prediction of relationships between the lifetime distributions to be observed for fibers under different loading histories: dead loads, loads proportional to time, and periodic loads. It also permits the calculation of relationships between the strength of separated individual filaments and the strength of bundles of filaments. The present formulation of the theory is more general than the author's previous work on this subject in that the fibers considered here can ``remember'' their past history as far as breakdown is concerned. It is shown that in the case of periodic loadings, depending on the choice of certain arbitrary functions, the theory can be used to discuss either time-dependent fatigue or cycle-dependent fatigue. The relationships between the present approach and the static models used in classical theories of tensile strength distributions for single filaments and bundles are discussed.
This article consists of a formal, axiomatic development of the theory. Future publications will contain detailed comparisons of the various results with available experimental data.
Space Charge Calculations for Semiconductors
Authors: Seiwatz Ruth , Green Mino 
Published: April 2005

The electric field at the surface of a semiconductor is obtained as a function of the semiconductor bulk properties and the potential difference across the space charge region. The treatment is general enough to take into account degenerate free carrier distributions and partial ionization of impurities, either in the neutral bulk or the space charge region, or both. A one-dimensional model with a spacially homogeneous impurity distribution is assumed. The density of states in the conduction and valence bands is assumed to be that appropriate for spherical and ellipsoidal energy surfaces. The common model for simple donor and acceptor states is used in the main body of the paper. Conditions under which the equation for the field can be conveniently simplified are discussed, and a particular case is treated numerically.
The validity of the free carrier distribution functions in the high fields near the semiconductor surface is discussed in Appendix I. The equation for the electric field at the semiconductor surface where the bulk impurities are described by a general model is given in Appendix II.
Experiment on the Electron Phase Microscope
Authors: Kanaya Kōichi , Kawakatsu Hisazo , Itō Kazuo , Yotsumoto Haruo 
Published: April 2005

A method of electron phase microscopic observation is described which offers greater image contrasts for specimens possessing small phase differences than is possible with conventional methods of electron microscopic observation.
It is shown that observation by dark contrast image using a phase plate, consisting of many holes in a carbon membrane, is very suitable for microtome section specimens as well as for thin crystal specimens, without a decrease in resolving power.
On Asperity Distributions of Metallic Surfaces
Authors: Ling F. F. 
Published: April 2005

A distribution of surface asperities is proposed for the case in which both mating surfaces are rough and asperities are in the form of right circular cones. The assumption of this particular asperity form is suggested by roughness measurements of ground steel, brass, and aluminum which yielded similar results for stylus traversing parallel, 45°, and perpendicular to lay. Considering the mating cones perfectly plastic and distributed in the proposed manner, bulk deformation-load is related to compliance.
The essential finding is that the load-compliance characteristics for mating surfaces having comparable roughness have slopes much steeper than those predictable by previous theories, all of which involve the assumption that one of the surfaces is smooth and rigid. A simple experiment is described in which load and compliance are measured. Results seem to support the plausibility of the proposed theory. Moreover, this plausibility shows promise of the calculation of other bulk-quantities such as frictional resistance.
Ultrasonic Measurement of Polarization Switching Processes in Barium-Titanate Single Crystal
Authors: Husimi K. , Kataoka K. 
Published: April 2005

A previously developed nondestructive piezoelectric method for studying the state of polarization of ferroelectric crystals is applied to study polarization switching in barium titanate single crystals.
We propose three polarization processes. The first and second processes were designated nucleation and growth by Merz. The third process cannot be measured by conventional pulse methods, and has a very slow polarizing velocity. This indicates the existence of layers which lie between the surface layer and inner layer.
Switching time results are considered in the light of the above experiments.