bluuebunny/crossref_metadata_2025 huggingface dataset:
Resonant Modes of Ferromagnetic Spheroids
Authors: Walker L. R.
Published: April 2005

The spectrum of modes of oscillation of a ferromagnetic spheroid situated in a uniform dc magnetic field is discussed. It is shown that, for the size of sample usually used in microwave experiments, a part of the spectrum consists of magnetostatic modes for which exchange and propagation may be ignored. The behavior of these modes is discussed at some length and it is shown that the analysis gives a satisfactory description of the observed absorption curves.
Ferromagnetic Resonance in Polycrystalline Nickel Ferrite Aluminate
Authors: Schlömann E. , Zeender J. R.
Published: April 2005

Line broadening because of crystalline anisotropy and the random orientation of the crystallites is investigated for the case in which the anisotropy field is much larger than the saturation magnetization. The theory predicts an absorption line with shoulders on each side which correspond to grains in which a hard or an easy direction is aligned with the dc field. With increasing anisotropy the low-field side of the line becomes more prominent and for γHa/ω≳·5 a secondary absorption peak occurs on the low-field side of the main resonance. Measurements in nickel ferrite aluminates at X band agree reasonably well with the predictions, if it is assumed that the first order anisotropy constant is negative and that all higher order anisotropy constants are zero.
Damping and the Dispersion Relations in Antiferromagnetic Resonance
Authors: Dayhoff E. S.
Published: April 2005

The tensor susceptibility of an antiferromagnetic with uniaxial anisotropy has been calculated using several modifications of the Bloch damping term. The axial component of the susceptibility is particularly simple and is readily tested by the Kronig-Kramers dispersion relations as modified by Gourary. It is found that, of the damping terms considered, only one which includes relaxation to the instantaneous equilibrium magnetizations will pass this test.
Effect of Sample Thickness on the Field Annealing of 6.5% Si–Fe
Authors: Albert P. A.
Published: April 2005

Iron alloys containing about 6.5 weight percent silicon are known to respond to heat treatment in a magnetic field. Since the degree of response has been observed to vary with sheet thickness, a study was made to better define this variation.

Two different alloy compositions were cast in cylindrical molds. The ingots were drilled to form hollow cylinders which were sliced and polished to rings of final thicknesses of from 0.150-in. to 0.0025-in.

dc hysteresis loops were measured on samples as annealed 2 hours at 1000°C in dry hydrogen, and as subsequently cooled at 40°C/hr from 900°C in a circumferential magnetic field of 10 oe.

The differences in coercive force and maximum permeability between samples field annealed and not field annealed are thickness dependent, and are greater for thicker samples.

The effects of thickness on coercive force are lessened by electropolishing, which greatly reduces the slope of the Hcvs (1/d)-curve for both the field-annealed and not field-annealed states. The maximum permeability is not found to be affected by electropolishing.
Low Residual Induction in High-Aluminum Iron Alloys
Authors: Pavlovic D. , Foster K.
Published: April 2005

Low values of residual induction have been observed for different heat treatments in 0.007 and 0.014 in. thick sheets of aluminum-iron alloys containing 10 to 16 weight percent aluminum. For these materials the ratio of residual induction (Br) to induction at 100 oersteds (B100) gave values of 0.05 to 0.1. These low residual induction values apparently occur at compositions having zero crystal anisotropy for both furnace-cooled and water-quenched alloys. Domain patterns were observed in these low Br alloys but, in general, no evidence of domain patterns was observed in the same alloys when the Br/B100 ratio was increased, through suitable heat treatment, to a value greater than about 0.2. The fairly high magnetostriction of the alloys around the Fe3Al composition and the stress produced by cooling through differently ordered regions may be considered to produce a high ``stress anisotropy'' resulting in pronounced domain patterns and perhaps also to contribute to the lowering of the residual induction of these alloys.
Some Properties of Quenched Magnesium Ferrites
Authors: Epstein D. J. , Frackiewicz B.
Published: April 2005

A study has been made of the magnetic properties of the system of quenched magnesium ferrites (MgxIIFe1−xIII) · (Mg1−xIIFe1+xIII)O4, where x, the fraction of magnesium ions in tetrahedral sites, varies from 0.14 to 0.26. Included among the properties examined are: saturation moment, Curie point, initial permeability, and coercive force. A limited study of the kinetics of the cation redistribution has also been made. Samples quenched from 1100°C and then tempered at 600°C require somewhat less than 16 hours to attain an equilibrium cation distribution at the latter temperature. The approach to equilibrium is consistent with a model in which the rate of approach is proportional to exp(−θ0′+θ1′x)/T where θ0′ and θ1′ are activation constants.
Some Magnetic and Crystallographic Properties of the System LaMn1−xNixO3+λ
Authors: Wold A. , Arnott R. J. , Goodenough J. B.
Published: April 2005

The system LaMn1−xNixO3+λ has been prepared under varying conditions for the entire range of compositions 0≤x≤1. The saturation magnetization, lattice parameters, and chemical analysis have been measured for each sample. The origin of discrepancies in the literature on the crystal structure of LaMnO3 is shown to be due to different preparation procedures which result in the presence of differing amounts of Mn4+: the lattice symmetry changes from orthorhombic to rhombohedral as the Mn4+ concentration exceeds 21% of the total manganese. The system is ferromagnetic with magnetization only slightly less than the spin-only value over the compositional range 0.2≤x≤0.5: a ferromagnetic Ni3+–Mn3+ interaction is indicated. The system remains orthorhombic throughout the range 0≤x<0.5; it shows an increasing distortion to an apparently monoclinic symmetry in the range 0.5<x≤0.8. LaNiO3 is rhombohedral at room temperature. The lattice symmetry is compatible with Ni3+ in a low-spin state: this is also in accord with the magnetization values. Qualitative concepts used to interpret the system (La,Ca)MnO3 are applied to interpret the magnetic and crystallographic properties of this system as well as the magnetic properties of some rhombohedral perovskite-type systems rich in Mn3+ ions.
Antiferromagnetic Structures of MnS2, MnSe2, and MnTe2
Authors: Corliss L. M. , Elliott N. , Hastings J. M.
Published: April 2005

The antiferromagnetic structures of MnS2, MnSe2, and MnTe2 have been obtained by neutron diffraction. The disulfide exhibits ordering of the ``third'' kind, the ditelluride, ordering of the ``first'' kind, and the diselenide, an arrangement which is intermediate between the two. The structures are discussed from the viewpoint of indirect exchange.
Energy Distribution in Partially Ferrite-Filled Wave Guides
Authors: Tompkins J. E.
Published: April 2005

The theory of wave propagation in circular wave guides containing coaxial longitudinally-magnetized ferrite rods is examined for cases where the rod diameter is too large for accurate perturbation treatment. Several solutions of the transcendental equation have been computed with the aid of experimental data. Field distribution and energy concentration data thus obtained are given for several cases for positive and negative rotating waves.
Performance of Permanent Magnets at Elevated Temperatures
Authors: Roberts W. H.
Published: April 2005

The objective of this investigation was to determine the effect of temperature up to 600°C and vibration on the performance of Alnico V and Alnico VI magnets. Data is presented on the effect of cycling stability, coefficient of remanence, extended exposure to elevated temperature and vibration.

The results of this investigation show that the use of Alnico V and Alnico VI in most instrument and control applications is feasible up to 500°C. However, a considerable loss in properties should be expected if the temperature exceeds 500°C.
Microuniformity of Permanent Magnets
Authors: Mendelsohn L. I.
Published: April 2005

A measurement system was developed to measure variations in the flux density normal to the pole faces of short axially-magnetized cylindrical permanent magnets. A quartz crystal vibrated a single-turn pickup coil to scan an area 0.028 in.×0.00002 in. at a distance of 0.010 in. from the pole face. Circumferential variation of flux density was used as the uniformity criterion. For magnets compacted from powders variations may be held to less than 4% of the average. Directional materials such as cast Alnico V show variations as high as 17%.
Understanding and Predicting Permanent Magnet Performance by Electrical Analog Methods
Authors: Parker R. J.
Published: April 2005

Permanent magnet performance problems are by their nature cut and try and an optimum solution in even a simple application requires considerable time and effort and is to some extent an art. As advances in the technology of making the permanent magnet allow a wider range of magnetic properties and physical arrangements the need increases for a firm engineering approach in this problem area. In this paper the author describes a complete data system and apparatus using electrical analogs in which the unit properties of a permanent magnet and its external loading may be conveniently set up and varied.

Constant voltage sources and linear resistance elements with predetermined switching points allow the nonlinear B-H relationship to be set up for any permanent magnet material.

The magnet volume and the space surrounding the magnet structure is zoned in a unique manner which allows leakage permeance from each zone to be lumped and estimated from charts as a function of magnet surface area and circuit configuration in terms of resistance.

Zoning allows an accurate integration of magnetomotive force and the effective magnetomotive force is associated with each leakage zone so that each zone adjust itself to a point on the B-H curve as dictated by the loading it sees, exactly simulating the actual magnet conditions. Rules of thumb and experience factors are minimized and accuracy is only limited by the correctness of the lumped permeance values.

Permeance data for the program has been developed and plotted as families of curves relating geometry and effective permeance. Formulas, measurements on existing magnet structures, and electrostatic capacitance measurements have been used extensively to prepare valid permeance relationships.

Easily changed electrical quantities allow rapid exploration of combinations of unit properties and circuit geometry by reading meters calibrated in terms of B and H for each zone. Useful gap flux and the external energy in each space zone are also easily read on meters.

Having established the electrical circuit representing the permanent magnet and its external field it is also possible to simulate minor loop operation and to meter the change in potential energy as it is alternately stored in the magnet and returned to the external field as the external load is changed over the operating cycle. This simulation of the dynamic function of the magnet is of value in accurately estimating force-distance relationships in mechanical work applications and in the analysis of the permanent magnet generator problem involving stability and performance under various load conditions.
Some Aspects of Tempering 3¼% Silicon Steel as Followed by Time Decay of Permeability
Authors: Anolick E. S. , Singer Joseph
Published: April 2005

The time decay of permeability has been employed in the study of the distribution of interstitials (C,N) in 3¼% Si-Steel. In following the 150°C tempering of slowly cooled samples, a reversion phenomenon is noted. A method is discussed for obtaining the solubility of carbon over a limited range of temperature, with some preliminary results included.
New Type of Ferromagnetic Amplifier
Authors: Hogan C. L. , Jepsen R. L. , Vartanian P. H.
Published: April 2005

A simple physical explanation is given of the mechanism of microwave amplification by coupling local oscillator energy to signal energy as proposed by Suhl.
Ferromagnetic Resonance in Yttrium Iron Garnet at Low Frequencies
Authors: Spencer E. G. , LeCraw R. C. , Porter C. S.
Published: April 2005

Single crystals of yttrium iron garnet (YIG) exhibit the narrowest resonant line of all known ferromagnetic materials, being as low as 2.3 oe for the full width at half height for polished spheres at 9300 mc. Ferromagnetic resonance on polished YIG disks was observed at frequencies as low as 44 mc, for an applied dc field of 1000 oe. Conversely, resonance was observed for fields as low as 300 oe, for a frequency of 2000 mc.

Nonlinear effects in ferromagnetic materials can be evidenced by the excitation of unstable spin wave modes, such as were discovered at x band by Bloembergen and his colleagues. In their case the dc fields required for this subsidiary resonance were approximately one half that required for resonance of uniform precession. When measurements are made on a sphere at a frequency low enough so that Hres<8πMs/3, Suhl's theory shows that the dc field required for the minimum threshold of the subsidiary resonance is identical with that required for resonance of the uniform precession. In this case the critical rf fields required are particularly low being given in terms of the line width to an order of magnitude as hcrit=ΔH2/4πMs.

Measurements have been made of hcrit, for the subsidiary resonance as a function of frequency for polished single crystal spheres of YIG. Based on a 4πMs of 1725, the frequency below which coincidence of the uniform precession and subsidiary resonances occur, is 3220 mc. Below 1610 mc the dc fields for resonance are insufficient to saturate the sphere and domains are formed. Values are given for hcrit, spin-wave angle θ, and spin-wave number k for frequencies of 1610 to 3220 mc. At 2200 mc a min in hcrit occurs. At this frequency hcrit=2.0 millioersteds, the power incident on the cavity is 20 microwatts and the power absorbed by the sample is of the order of a microwatt. The experimental results are discussed in terms of Suhl's theory.
Magnetocrystalline Anisotropy of Mg–Fe Ferrites: Temperature Dependence, Ionic Distribution Effects, and the Crystalline Field Model
Authors: Folen V. J. , Rado G. T.
Published: April 2005

The magnetocrystalline anisotropy constant (K1) and saturation magnetization (Ms) of magnesium-iron ferrite monocrystals containing 6 to 50 mole percent magnetite were measured as a function of temperature (T) and ionic distribution. For crystals containing 6 to 25 mole percent magnetite, K1 was found to vary more rapidly with temperature when the ionic distribution in a crystal corresponds to a relatively high Ms than when it corresponds to a relatively low Ms in the same crystal. The observed changes in K1 resulting from alterations of the ionic distribution are shown to be consistent with a phenomenological one-ion anisotropy model. On this basis, the measurements yield a positive anisotropy for a ferric ion in a tetrahedral site (A) and a negative anisotropy for this ion in an octahedral site (B). Finally, the data obtained on one Mg-Fe ferrite crystal (containing 6 mole percent magnetite) were used in the Yosida-Tachiki anisotropy theory. The ferric ion cubic crystalline field splitting parameters aA and aB occurring in this theory were determined for two different states of ionic distribution in the crystal. It was found that aA = −0.0092 cm−1 and aB = +0.0232 cm−1 for the state corresponding to a relatively high Ms, and aA = −0.0135 cm−1 and aB = +0.0250 cm−1 for the state corresponding to a relatively low Ms. The theoretical anisotropy curves obtained by using these a values are in very good agreement with experiment. Furthermore, the aB values agree with aB = +0.0205 cm−1 determined by Low from paramagnetic resonance measurements on ferric ions in MgO.
Crystallographic and Magnetic Studies of the System (NiFe2O4)1−x + (NiMn2O4)x
Authors: Baltzer Philip K. , White John G.
Published: April 2005

The system (NiFe2O4)1−x + (NiMn2O4)x was selected to study the role of the Mn3+ ion in determining the crystallographic and magnetic properties of spinels. The ionic distribution was investigated by means of x-ray diffraction. A cubic spinel structure is obtained throughout the system, the lattice parameter increasing monotonically with x from 8.34 to 8.39 A. It is found that in the range 0≤x≤0.5 that manganese progressively replaces iron on the six-coordinated sites whereas, in the range 0.5≤x≤1, the manganese progressively replaces iron on the four-coordinated sites. Therefore, manganese is not able to displace nickel from the six-coordinated sites and NiMn2O4 is a cubic inverse spinel. These results are consistent with the thesis that the tetragonal distortions of ZnMn2O4, Mn3O4, MgMn2O4, and Li0.5Mn2.5O4 are because of the six-coordinated sites in these compounds essentially all being occupied by manganese ions. Magnetostriction measurements were made as a function of applied field to determine the sign and order of magnitude of the magnetic anisotropy of the polycrystalline samples. The magnetic anisotropy is found to pass through zero with increasing x, becoming highly positive (K≃+105 ergs/cc) at x=0.5. Heretofore only the Co2+ ion has been found to produce a positive anisotropy in the spinel structure. Magnetic moment measurements indicate that all of the manganese is trivalent in the range 0≤x≤0.5. However, magnetic moment measurements over the range 0.5≤x≤1 indicate that at x=1, NiMn2O4, the manganese is divalent and quadravalent on the four- and six-coordinated sites respectively. NiMn2O4 appears to become ferrimagnetic at approximately 100°K.
Origin of Magnetic Anisotropy in CoxFe3−xO4
Authors: Slonczewski J. C.
Published: April 2005

A model is proposed to explain the large part of the ferromagnetic anisotropy energy of CoxFe3−xO4(where x is small) which is caused by the presence of Co2+. The residual orbital angular momentum α(∼) of Co2+ is constrained by the crystal field to lie parallel to the axis of threefold symmetry. Spin-oribt energy λL·S couples the spin to this axis, accounting for the anisotropy energy. By fitting the theory to experimental anisotropy data, one finds that |αλ| = 132 cm−1. The assumption that cations are mobile at higher temperatures leads to an explanation of the anisotropy induced by magnetic annealing.
Relationship between Single Crystal and Effective Polycrystalline Anisotropy Constants in Ferrites
Authors: Kriessman C. J. , Harrison S. E. , Belson H. S.
Published: April 2005

In polycrystalline ferrites the natural spin resonance of electrons in the effective resonance field, detected by initial permeability measurements, allows the determination of an effective anisotropy constant, Ke. It is shown from measurements of K1 on single crystals by microwave techniques that Ke=2K1. This result is based on work on Mn1+xFe2−xO4, NiFe2O4, and MgFe2O4.
Exchange Anisotropy in the Iron-Iron Oxide System
Authors: Meiklejohn W. H.
Published: April 2005

Exchange anisotropy is the result of a magnetic interaction between a ferromagnetic and an antiferromagnetic system. This interaction was discovered in the Co–CoO system, wherein cobalt is the ferromagnetic and cobaltous oxide is the antiferromagnetic system. The material consisted of fine particles (∼200 A) of cobalt which had a coherent cobaltous oxide film. Above the Néel temperature where the CoO is the paramagnetic state the material had the expected behavior of a ferromagnetic. Below the Néel temperature the interaction between the ferromagnetic cobalt and the antiferromagnetic cobaltous oxide resulted in a displaced hysteresis loop and a nonvanishing value of the rotational hysteresis for applied magnetic fields greater than 2K/Is. Further investigation of the temperature dependence of this system has shown that the high field (H>2K/Is) rotational hysteresis vanishes precisely at the Néel temperature of cobaltous oxide.

Work on the Fe–FeO system has shown a nonvanishing value of rotational hysteresis for temperatures below the Néel temperature of FeO and for magnetic fields greater than 2K/Is for iron. The temperature dependence of this high field rotational hysteresis shows that it vanishes at precisely the Néel temperature of FeO.
Magnetostriction and Elastic Properties of Ferromagnetic Substances at High Magnetic Fields
Authors: Sato Hiroshi
Published: April 2005

The manner in which the anisotropic forced magnetostriction contributes to the magnetostriction of ferromagnetic substances at high magnetic fields is discussed from a localized model of ferromagnetism. With this assumption, the free energy of a ferromagnetic substance can be conveniently divided into several terms and it can be concluded quite naturally that a free-energy term corresponding to that of ferromagnetic anisotropy gives rise to an anisotropic forced magnetostriction. In the past, the isotropic forced volume magnetostriction has been considered to be the only cause of the forced magnetostriction. This is probably one reason for the discrepancies between the experimental value of the volume magnetostriction and the theoretical value expected from the pressure dependence of the Curie point, etc.

From a similar point of view, anomalous behavior of elastic properties of a ferromagnetic substance, such as the change of the temperature coefficient of the elastic constants at the Curie point, the dependence of the elastic constants upon the direction of the magnetic field, etc., are explained as an intrinsic change in the elastic constants with spontaneous magnetization. In the past, these effects have been explained only as a result of the deformation of the crystal lattice due to the spontaneous magnetostriction (volume effect, morphic effect).
Domain Wall Motion in Metals
Authors: DeBlois R. W.
Published: April 2005

A brief review on the ferromagnetic domain wall is first presented, touching on its energy and thickness, its coercive force, and its motion in metal loops, tapes, and wires, as governed by eddy currents and by relaxation processes. Next to be presented are the experimental results of an extension of the Sixtus-Tonks experiment to axial domain wall velocities over 50 km/sec, made possible by use of nearly perfect iron whiskers. Plots of axial velocity vs applied field are nonlinear and in some cases show velocity discontinuities at room temperature in the region 3 to 8.5 km/sec. At 77°K velocity discontinuities beginning at 2 km/sec are observed. Nucleating fields of over 250 oersteds are indicated. Data analysis yields a relaxation damping coefficient, βr≈10 g/sec cm2 for normal domain wall motion.
Temperature Dependence of the Absorption of Ultrasound in a Nickel Single Crystal from 77° to 650°K
Authors: West Forrest G.
Published: April 2005

The temperature dependence of the difference between the demagnetized and saturation ultrasonic absorptions has been measured between 77° and 650°K. From 77° to above 400°K, at 10 mc sec−1, this difference is found to be inversely proportional to the first-order magnetocrystalline anisotropy constant K1 to approximately the first power. This result shows the inadequacy of present theories of absorption based on microeddy current losses accompanying domain wall motion and domain rotation. Further evidence is presented which seems to definitely exclude the rotation mechanism for this frequency range in nickel.
Improved Torque Magnetometer
Authors: Byrnes W. S. , Crawford R. G.
Published: April 2005

A new automatic recording torque magenetometer has been designed and constructed. This instrument will automatically plot the torque exerted on a thin ferromagnetic disk slowly rotating in a uniform magnetic field as a function of the angle between a reference direction in the disk and the direction of the applied field. The torque exerted on the disk is converted into a dc electrical signal. Conversion is accomplished by coupling the mechanical torque system to a strain gauge transducer whose electrical output is used to drive a dc strip chart recorder.

This type of torque magnetometer was first designed by D. S. Miller. Emphasis is placed on various design features of the new magnetometer that are considered improvements over the original. In particular improvements have been made on the bearings, shaft, and strip which constitute the important features of the instrument. Depending on the transducer that is used, the measurable torque range is 0 to 70×103 ergs. The sensitivity of the highest range is approximately 2×103 ergs/mv.
Transparent Ferromagnetic Light Modulator Using Yttrium Iron Garnet
Authors: Porter C. S. , Spencer E. G. , LeCraw R. C.
Published: April 2005

A method of preparation of yttrium iron garnet crystals from Y2O3 and Fe2O3, using PbO as a solvent, is described. The transmission spectrum from 0.5 to 16 μ of ground and polished slabs cut from the crystals shows strong absorption at wavelengths shorter than 0.7 μ; other absorption occur at 0.89, 5.7, 7.8, 8.6, 10.9, 11.6, and 14 μ. Faraday rotation brought about by spontaneous magnetization normal to the slab can be applied to the design of light modulators. Three of these are described and the construction and operation of one is discussed. It is an axially ac magnetized slab, passing polarized tungsten light to an analyzer 45° out of the plane of polarization.
Casting of Alnico VII with Improved Physical Properties
Authors: Wenny D. H. , Olsen K. M.
Published: April 2005

Alnico VII having the highest coercive force Hc = 1000 of the Alnico alloys has not come into extensive use because of its brittleness. Studies in the metallurgical laboratories show that highly purified Alnico VII castings melted under a hydrogen atmosphere are just as brittle as castings air melted with standard raw materials. On the other hand, silica shell molds which cut the initial average cooling rate of the castings to about 20°C per min afford a convenient way to cast sound crack-free Alnico VII magnets which can withstand the handling and thermal shock of the subsequent heat treating process. Satisfactory magnetic quality and chemical uniformity are obtained by air melting standard raw materials of commercial purity. The magnets are amenable to cutting and grinding and have an excellent surface. Though the molds are costly, and their fragile nature necessitates careful handling, the use of silica shell molds will produce an Alnico VII with good magnetic and physical properties.
Suggestion Concerning the Role of Wave-Function Symmetry in Transition Metals and Their Alloys
Authors: Goodenough John B.
Published: April 2005

Past attempts to describe the d electrons of the transition metals have been based on one or the other of two extreme views: the one, the conduction-band model, treats the d electrons as though they belong to the lattice as a whole rather than to particular atoms; the other, the shell model, treats the d electrons as though they are completely localized. The purpose of this paper is to point out that the relative symmetries of d wave functions and the lattice geometry should determine which d electrons may be approximated by a localized, or shell, model, which electrons would be better approximated by bonding molecular orbitals, and which electrons may be treated by the conduction-band approximation. The b.c.c. metals are particularly discussed since in this lattice geometry, two of the d wave functions are directed toward next-nearest neighbors and away from the eight nearest neighbors whereas three of the wave functions are strongly perturbed by the nearest neighbors. It is pointed out that electrons which occupy states involving the former wave functions should be localized whereas electrons which occupy states involving the latter wave functions are best described by a molecular orbital: it is further pointed out that a possible description of the molecular orbitals in question is a bonding t2g band. In this model the conduction band is a valence band composed of an s and three p orbitals. From a knowledge of the Hall constants and the magnetic characteristics of chromium and iron, a schematic density-of-states curve is constructed.
Magnetic Domain Patterns on Iron Whiskers
Authors: Coleman R. V. , Scott G. G.
Published: April 2005

Magnetic domain patterns have been observed on iron whiskers growing in [111], [100], and [110] directions. In most cases the patterns on unmagnetized whiskers are very simple and subject to straight forward interpretation. Patterns on {100} faces have been observed to change after annealing above the Curie temperature. Domain arrangements have been observed which produce intersecting boundaries at the crystal surface which do not collect magnetite. Dagger patterns which form on {110} surfaces under application of normal fields have been studied and the effect of misoriented surfaces on these patterns has been investigated.
Domain Observations on Iron Whiskers
Authors: DeBlois R. W. , Graham C. D.
Published: April 2005

We have confirmed the appearance in iron whiskers of domain walls which apparently violate the restriction that the normal component of magnetization must remain constant across the wall. These walls sometimes have a dotted or serrated appearance. We have found such walls in a closure domain structure which permits the calculation of an approximate value for the surface energy of the serrated wall; this energy is approximately ten times the energy of a normal 90° wall or five times the energy of a normal 180° wall. We conclude that the serrated wall contains an inner structure which largely eliminates any free poles.
Magnetization Reversal by Rotation
Authors: Gillette P. R. , Oshima K.
Published: April 2005

The mechanism of magnetization reversal by simple rotation has been discussed by a number of authors, but a completely general analysis (applicable to a single-domain ferromagnetic body of any type of anisotropy, with an applied field in an arbitrary direction) has not been given. The purpose of this paper is to present such an analysis. General differential equations are derived which can be used to describe the rotation process in any body for which demagnetization and anisotropy factors can be written. These equations are then applied to a sphere, a cylinder, and a thin sheet. Both uniaxial and cubic anisotropy are considered for the sphere and cylinder; only uniaxial anisotropy (the kind observed in deposited films) is considered for the thin sheet. The resulting differential equations can be solved numerically to obtain output voltages, switching times, and switching constants.
Calculation of the Energy Loss in Magnetic Sheet Materials Using a Domain Model
Authors: Pry R. H. , Bean C. P.
Published: April 2005

The energy loss resulting from eddy currents is calculated for magnetic sheet materials with a simple domain configuration. The domain model used is considered to be applicable for any induction up to saturation and for the frequency range up to that used in most electrical power applications. The eddy current losses have been calculated explicitly for the case of sinusoidal induction excitation, and expressed in terms of the ratio of domain wall spacing to sheet thickness. The results are in a form more suitable for quantitative comparison with measured values on materials, such as grain oriented silicon iron, than have been available.
Growth of MnBi Crystals and Evidence for Subgrains from Domain Patterns
Authors: Ellis W. C. , Williams H. J. , Sherwood R. C.
Published: April 2005

MnBi crystals have been prepared by crystallization in a temperature gradient from a liquid solution of bismuth saturated with manganese. Informative domain patterns have been developed on surfaces of a crystal by the normal Kerr magneto-optic effect and by the Bitter technique. Block patterns, obtained in some instances, have been interpreted as evidence for subgrain structure.
Constraint Principle in Ferromagnetic Domain Theory
Authors: Gold Louis
Published: April 2005

The need for a constraint principle is demonstrated by a more precise analysis of the classic Landau-Lifshitz (LL) domain configuration. A constraint minimization of the (LL) configuration leads to the requirement of increasing wall thickness in vanishingly small specimens. The Néel-Kaczer theory (NK), based on wall magnetostatic energy, also predicts variable wall thickness. But (NK) theory is formulated for (infinite) sheet thicknesses well above the thin film region and it requires a gradual fall off of wall size as the sheet thickness diminishes. The constraint calculation is characterized by a precipitous wall increase as the single domain realm is approached, a type of behavior that may have been observed in thin film experiments.
Sputtering of Surfaces by Positive Ion Beams of Low Energy
Authors: Honig Richard E.
Published: April 2005

Silver, germanium, and germanium-silicon alloy surfaces have been bombarded with the inert gas ions Ne+, A+, Kr+, and Xe+, at energies between 30 and 400 ev. Primary beam intensities between one and ten μa/cm2 were obtained in an oscillating electron source of the Heil type. The secondary particles sputtered off, neutrals as well as positive and negative ions, were identified and recorded in a 180° mass spectrometer of 5.5-inch radius. They are partly background gases adsorbed on the surface, partly atoms and molecules characteristic of the sample. Among the latter particles, neutrals were about 100 times more abundant than those emitted as positive ions. Rather low yields (about one sample atom per 100 incident ions with 400-ev energy) and relatively high threshold energies (40–50 ev for an angle of 30° between beam and surface) are believed to be due to surface contamination. Retarding potential measurements showed that over 80% of the particles sputtered have initial energies of less than 5 ev. After bombardment, the Ge and Ge-Si surfaces showed oval-shaped hillocks, possibly due to appreciable carbon concentrations in the samples studied. If the effects of surface contamination can be reduced, this method promises to be useful in the analysis of solid surfaces.
On the Theory of Double Bloch Walls in Thin Films
Authors: Kaczér Jan
Published: April 2005

The paper gives a theory of the double Bloch walls observed by Williams and Sherwood in thin ferromagnetic films. The stability of these walls as a function of the thickness of the film and the external magnetic field is discussed.
Experiments in Liquid Atomization by Air Streams
Authors: Hrubecky Henry F.
Published: April 2005

Water is atomized by a high-velocity air stream using various methods of injection and water nozzle positions. Low water volume rates and velocities, air velocities up to acoustic, and ratios of air volume to water volume rates up to 25 000 were utilized. Results indicate water injection into region of maximum velocity, parallel to the air flow gives highest degree of atomization under similar conditions. Comparison is made with the Tanasawa-Nukiyama correlation and discrepancies in droplet sizes at high air velocities are found and discussed.
Measurement of Ternary Distribution Coefficients in Silicon
Authors: Navon David
Published: April 2005

A method is described for determining the distribution coefficient of an impurity introduced into a semi-conductor by a fused metal contact. Coefficients for the segregation of antimony, arsenic, gallium, and aluminum from a silver contact to silicon at 1250°C are less than at the silicon melting point (1408°C). Gold-doped contacts to silicon yield similar values for the distribution coefficient of these impurities. This value is independent of the concentration of the impurity in the gold or silver alloy for small (less than 1%) percentages of the impurity. At 1250°C, the segregation of aluminum from a dilute solution of aluminum in silver is about the same as from 100% aluminum.

The diffusivity of silicon atoms through a liquid zone containing aluminum and saturated with silicon is greater, at any particular temperature, than the diffusivity through a silver-silicon zone at the same temperature. However, these values approach each other at the silicon melting point.
Stability of an Electron Beam on a Slalom Orbit
Authors: Cook J. S. , Louisell W. H. , Yocom W. H.
Published: April 2005

A study is made of an electrostatic method of focusing an electron beam in a traveling wave tube in which the beam traverses a slalom-like orbit between the wires of the slow wave structure. The requisite field is produced by a row of equally spaced wires at the same potential placed midway between two parallel plates at another potential.

The equations of motion are solved to find initial conditions for stable orbits. Space charge effects are considered.

A large slalom tester was built to compare experimental and theoretical results. The agreement between the computed and measured current transmitted is surprisingly close. There is also good agreement between the measured and computed beam perveance.
Radiation Induced Noise in p-n Junctions
Authors: Fonger W. H. , Loferski J. J. , Rappaport P.
Published: April 2005

Noise is induced in a p-n junction when it is bombarded by high-energy radiation. The mean square noise current d〈(in)2〉 is predicted to be given by d〈(in)2〉=2e2〈NB〉〈m2〉Δf,where NB is rate of incidence of bombarding particles and m is the number of hole-electron pairs which reach the junction per primary particle. Experiments performed on Ge and Si p-n junction diodes agreed with this prediction. Extension of the theory to triodes is outlined, and applications of the noise in detecting and analyzing radiation are discussed.
Production of Dislocations During Growth from the Melt
Authors: Tiller W. A.
Published: April 2005

The segregation of solute on a microscopic scale during crystal growth leads to the introduction of dislocation lines into the crystal at the bounding surfaces of the segregate. A layer type of segregate resulting from platelet growth leads to dislocation densities of 103−106 lines/cm2. A cellular type of segregation resulting from cellular or dendritic growth leads to dislocation densities of 106−108 lines/cm2 in the crystal.
Heavy Moderator Approximations in Neutron Transport Theory
Authors: Amster Harvey
Published: April 2005

The flow of neutrons slowing down into a given angular and lethargy (or energy) interval equals an integral over the contributions from neutrons at other angles and lethargies within the medium. The two angular dependences of the integrand are commonly expanded in Legendre polynomials, and for heavy moderators, the lethargy dependence being integrated over is expanded in a power series about the lethargy of the exit neutrons. For each of these three expansions there is an index whose effect on the rate at which the resulting coefficients TLL'n vanish with increasing moderator mass is found. These estimates indicate where to terminate the lethargy expansions of the components of the current so as to maintain a consistent order of accuracy for each, and the sensitivity of the approximations to individual Legendre coefficients of the scattering cross sections follows. Exact recursion formulas derived for the TLL'n contain infinite sums, which can be terminated such that the uncertainty in the terms retained in the transport theory approximations are no larger than the estimated values of terms neglected. The familiar ``consistent P1 approximation'' is generalized as a particular example, and it is shown to be sensitive to only the first three Legendre coefficients of the cross section. The Greuling-Goertzel approximation is also generalized and its merits noted. The associated difficulties in treating recoil due to inelastic scattering are discussed.
Analysis of a Multipole State Separator and Focuser for Polarizable Molecules
Authors: Vonbun Friedrich O.
Published: April 2005

The electrostatic field of a multipole focuser, consisting of parallel rods arranged in a circle, is treated. The field equation is derived from the known field of a two-wire line, and results are given in the form of equations that express the field in terms of practical parameters. The field and the radial gradient of a (p+q)-pole focuser is compared to that of a p-pole focuser in order to indicate the value of increasing the number of poles.

Both a complete and a simplified set of differential equations (in cylindrical coordinates) of the path of polarizable molecules in this inhomogeneous field are also given. Based on the simplified differential equations, the path of a NH3 molecule in the J=K=3 (MJ=3) inversion state is graphically presented.
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 rolling 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 {100} <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.
Model for Solute Diffusion in Crystals with the Diamond Structure
Authors: Swalin R. A.
Published: April 2005

A theory for solute diffusion in crystals with the diamond structure such as germanium and silicon is derived by considering the effect of impurity ion size difference and also the coulombic interaction between impurity ions and charged vacancies. The theory is compared with experimental results reported for germanium and silicon and the agreement is considered quite good. The experimental observations that n-type impurities diffuse considerably faster than p-type impurities in germanium, whereas the opposite effect is observed in silicon, are explained by the theory. Because of the relation between the Fermi energy and vacancy acceptor level, the coulombic interaction is shown to be the predominating factor in germanium, whereas in silicon the size difference between impurity ions is shown to predominate.
Elastic Constants by the Ultrasonic Pulse Echo Method
Authors: Eros S. , Reitz J. R.
Published: April 2005

The elastic constants of single-crystal KCl and NaI have been measured by means of the ultrasonic pulse echo method using a wide-band amplifier to display the unrectified echo pattern directly. The experimental results agree with previous measurements made using other techniques. From detailed observations of successive echoes, made possible by the wide-band receiving unit, it was determined that the pulse was attenuated at the front, and at the same time elongated, due to reflection from the specimen-transducer interface. This effect turns out to be just what one would expect theoretically, and is responsible for the so-called ``transit-time error.'' The transit-time error may be as large as one vibration period of the fundamental frequency in the pulse, and is most pronounced for crystal samples in which the acoustic impedance is the same as that of the quartz transducer.
Volumes and Surface Areas of Pendular Rings
Authors: Rose Walter
Published: April 2005

A packing of spheres is taken as a suitable model of porous media. The packing may be regular and the sphere size may be uniform, but in general, both should be random. Approximations are developed to give the volumes and surface areas of pendular rings that exist at points of sphere contact. From these, the total free volume and interfacial specific surface area are derived as expressive of the textural character of the packing.

It was found that the log-log plot of volumes and surface areas of pendular rings vary linearly with the angle made by the line joining the sphere centers and the line from the center of the largest sphere to the closest edge of the pendular ring. The relationship, moreover, was found not to be very sensitive to variation in the size ratio of the spheres in contact.

It also was found that the addition of pendular ring material to various sphere packings results in an unexpected decrease in the surface area of the boundaries that confine the resulting pore space.
Evidence of Dislocation Jogs in Deformed Silicon
Authors: Dash William C.
Published: April 2005

Trails extending from dislocations in plastically deformed silicon have been observed by decoration and also by an etching technique which develops channels on a {111} plane. The trails extending from screws tend to follow parallel <110> directions; those from mixed edge and screw dislocations are generally not crystallographic. Cusps occur where the trails are joined to the dislocations. A type of work hardening is found wherein trails from one turn of a Frank-Read spiral obstruct the motion of subsequent turns. Trails are sometimes segmented or zig-zag and appear to be composed of small discrete sections. Reversal of the direction of motion of a dislocation when the applied stress is removed is indicated by inversion of cusps. The main features of these trails can be accounted for on the basis of nonconservative motion of jogs which inject vacancies or interstitial atoms into their paths.
Field Modulation of Liquid Induced Excess Surface Currents on Germanium p-n Junctions
Authors: Eriksen W. T.
Published: April 2005

The field modulation of liquid induced surface currents on germanium surfaces has been investigated. The field induced current is shown to conform to the behavior seen by liquid induced currents on germanium surfaces. The modulation increases with decreasing temperature down to the melting point of the liquid and then decreases radically to nearly zero. The modulation effect is seen only when polar liquid ambients are used. A qualitative explanation of the effect is discussed in terms of a model for current conduction in which the charge carriers move in the liquid outside of the semiconductor. The increased current with external field is thought to arise from the orientation of the dipoles in the liquid giving increased mobility to the charge carriers.