bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of Langmuir Probes to Study Ion-Electron Recombination
Authors: Kretschmer C. B. , Petersen H. L. 
Published: April 2005

Between about 0.1 and 20 mm Hg, ion concentration is related to the current collected by a negative cylindrical probe by the equation (in practical units) n=1.78×1013λe−1/2μ−5/8(Vprp)−1/4i5/8,where λe is the electron mean free path, μ is the ion mobility, Vp and rp are the probe voltage and radius, and i is the probe current per unit length. The plasma is not perturbed because the probe current is supplied by ionization occurring at the sheath boundary.
Using this equation, the following values of the dissociative-recombination coefficient α in cm3/sec were obtained from pulse discharge afterglow measurements: argon, 3.6×10−7 for high excitation and 1.4×10−6 for moderate excitation; oxygen, 2.0×10−6; mercury, 3.5×10−6. For nitrogen α was found to be proportional to pressure and equal to 1.7×10−7 at 1 mm Hg. For cesium the above equation does not apply, and the value α = 1.7×10−7 was obtained from experimental results using conventional probe theory. The frequency of three-body conversion of atomic to molecular ions was found to be 151 sec−1 for argon and 37 sec−1 for helium.
Modulation Broadening of NMR and ESR Line Shapes
Authors: Wilson G. V. H. 
Published: April 2005

An analysis is made of the phase sensitive detection of magnetic resonances at various harmonics of the modulation frequency. The results are applicable to any experiment in which phase sensitive detection is employed. A mathematical treatment of modulation broadening is developed. Unlike the Taylor expansion method this is applicable in all practical cases. Signal amplitude and line shape of Lorentz and Gaussian resonances are calculated for the first three harmonics as functions of the modulation amplitude.
Expressions which relate the Fourier coefficients of a modulation-broadened resonance line shape to those of the true integrated line shape are derived. The use of these expressions in correcting observed line shapes for modulation broadening is compared with that of another method involving the summation of a convergent series.
Mutual Interaction between Microplasmas in Silicon p-n Junctions
Authors: Ruge Ingolf , Keil Günter 
Published: April 2005

Mutual interaction between microplasmas in silicon p-n junctions was found to be present if the conducting time of microplasmas reaches the magnitude of 10−7−10−6 sec. Then a conducting microplasma may trigger the conduction of others. The resulting pulses show multistable levels. Several examples of such a pulse form, caused by the trigger process, are given.
Measurements have shown that the microplasmas investigated do not lie close together and that a cluster form for microplasmas is not a necessary condition for a mutual interaction.
A simultaneous, independent operation of several microplasmas was found to be very improbable if one or more of the working microplasmas reach pulse lengths of the order of 10−4−10−3 sec.
Formation of Diamond-Shaped Prismatic Loops in Quenched fcc Metals
Authors: Eikum Alf , Thomas G. 
Published: April 2005

The concept of dissociated prismatic dislocation loops is proposed to explain the formation of diamond-shaped loops observed in several metals after quench aging. The dissociated prismatic loop is composed of parallel segments on {111} planes having a/6 &lt;112&gt; Burgers vectors. It is shown that diamond-shaped loops form from either a triangular or hexagonal Frank loop, and once formed can rotate on the glide cylinder to any orientation between and including {111} and {110}.
Climb kinetics are qualitatively discussed in terms of the equilibrium separation of partials. The separation is approximately equal to the core radius (2|b|) in Al, but is large enough in Cu (∼12|b|) to be experimentally detected. These considerations may explain why large loops are not often observed in metals other than aluminum.
Proposal for a Two-Stage Semiconductor Laser through Tunneling and Injection
Authors: Wang Shyh 
Published: April 2005

In the present paper, an analysis of laser action in semiconductors is made, and a condition for population inversion is established. The radiation output is found to be proportional to the deviation from the equilibrium value of the occupancy of the allowed states including the states in the conduction and valence band and also the donor and acceptor states. Possible laser levels are discussed.
Following the general analysis, a scheme is proposed for laser action in covalent semiconductors where the top of the valence band and the bottom of the conduction band do not occur at the same value of k. The scheme consists of simultaneously tunneling electrons into the (000) valley of the conduction band and injecting holes into the valence band. The outstanding feature of the proposed scheme is that it offers a definite possibility for separate amplitude and frequency modulation of the laser output. Various losses associated with the proposed scheme are also discussed.
Flow of a Rarefied Gas between Two Parallel Plates
Authors: Cercignani Carlo , Daneri Adelia 
Published: April 2005

The Poiseuille flow of a rarefied gas between two parallel plates is analyzed numerically for an inverse Knudsen number ranging from 0 to 10.5. The Bhatnagar, Gross, and Krook model is used and the transport integrodifferential equation is reduced to a purely integral one, which is solved numerically by the discrete ordinate method.
The plot of the volume flow rate vs pressure is shown to have the expected minimum; besides, it fits well with experimental results and previous approximate calculations.
In particular, the results given by Takao, properly corrected, are in good agreement with ours.
Longitudinal Permeability in Thin Permalloy Films
Authors: Torok E. J. , White R. A. 
Published: April 2005

Longitudinal permeability is defined as μL=(∂BL/∂HL)HT=const, where BL is the component of applied field parallel to the easy axis, and HT is a bias field applied perpendicular to the easy axis of a magnetic film with uniaxial anisotropy. The longitudinal permeability is also the hard axis resonance amplitude in the low frequency limit.
The longitudinal permeability is calculated using three different models. The first, that of an ideal single domain film, yields an infinite value when the bias equals HK. Considering the effect of inhomogeneity in easy axes, resulting in many noninteracting domains, gives a maximum μL/μT=22α90−23, where μT=4πM/HK and α90 is so defined that 90% of the film has a local easy axis within α90 degrees of the average easy axis. Including variation of HK within a film lowers μL/μT at HT=HK to 22α90−23−34α90−1Δ9012, where Δ90 is defined so that 90% of the film has an HK within Δ90 HK of the average HK of the film.
Comparison with experimental curves for films with measured values of α90 and Δ90 shows that the last model yields good qualitative agreement and correctly predicts the behavior of μL/μT with finite drive fields, but quantitatively the experimental maxima are 20% to 60% lower than the theoretical curves. This difference is attributed to wall energy terms which are not included as part of the regular calculation.
Detection of Low-Intensity Magnetic Fields by Means of Ferromagnetic Films
Authors: West F. G. , Odom W. J. , Rice J. A. , Penn T. C. 
Published: April 2005

This paper describes a sensitive field magnetometer which utilizes a ferromagnetic film as the sensitive element. Typical vacuum-evaporated films of Ni–Fe of approximately 80% Ni composition are used. These films are chosen to have small directional dispersion in the uniaxial anisotropy. It is well known that in the absence of other magnetic fields the application of a cyclically varying field (of amplitude greater than the anisotropy field) perpendicular to the average anisotropy axis causes the film to split into domains parallel to that axis. The net flux which cuts a sensing coil, the axis of which is parallel to the domains, remains zero during such cyclic magnetization. If there is a small component of field along the anisotropy axis, however, the net flux is proportional to that field. The induced voltage in the sensing coil indicates the direction and magnitude of the axial component of an ambient field. This principle forms the basis of the present device.
In practice, a sinusoidal rf (4 Mc) field drives the film along the perpendicular direction. A modulation field is applied along the average anisotropy axis. The output of the sensing coil is a modulated rf signal which is diode-rectified and phase-detected. In the absence of an ambient field along the anisotropy axis, the detected signal is of a frequency twice that of the modulation field. An ambient field along the axis causes the fundamental frequency of the modulation field to appear. The amplitude of the fundamental is proportional to the ambient field for small fields, while the phase is determined by the direction of the field. Fields having frequencies from dc to roughly 0.1 the modulation frequency can be detected in this manner. The smallest field so far detected by this device is of the order of 10−6 Oe in a dc to 1 cps bandpass.
Waffle Iron—a New Memory Structure
Authors: Smith J. L. 
Published: April 2005

The waffle iron is a short bit-length, closed flux-path, magnetic storage device. It consists of a high permeability base plate into which orthogonal slots have been cut, leaving a sequence of rectangular posts, giving the surface the appearance of a miniature waffle iron. To complete the array, a wiring pattern is placed into the slots and an overlay of square-loop magnetic material is laid across the tops of the posts. A closed flux-path structure consisting of a short length of this square-loop material and a longer length of high permeability material is thus formed by each pair of posts. Because of the structure of the device almost complete machine manufacture seems feasible.
Many experimental models of both destructive and nondestructive read memories have been built. All of the models feature the ``two-core per bit'' type of operation, and consequently, have good operating margins. One model, which has been tested extensively, has a 0.030-in. bit length. It is a linear select memory and has an output of greater than 100 mV with a duration of 0.25 μsec for a read current of 0.8 A. The write requirements are 0.3-A word and 0.15-A bit current with an allowable variation on each of ±35%. Time to write is 2 μsec. A second model which has been tested extensively is an electronically alterable, nondestructive read memory of the bimagnetic material type. The read repetition rate is greater than one megacycle and the write time is 5 μsec. With a bit length of 0.020 in. the read, word-write, and bit-write currents are 0.35 A, 0.45 A, and 0.3 A, respectively. The word- and bit-write currents have an allowable variation of ±35% each.
Experiments with memory arrays using the waffle-iron technique have shown that bit lengths of 0.005 in. or less and read-write cycle times of less than 0.5 μsec are feasible. With such short bit lengths, both the packing density and the field efficiency are high, (approximately 1000 bits per square in. and 100 Oe per A). Consequently, the waffle-iron structure is suitable for high-speed memory applications, where small size and potentially low drive currents are of prime importance.
Rotating-Field Technique for Galvanomagnetic Measurements
Authors: West Forrest G. 
Published: April 2005

The isothermal galvanomagnetic behavior of an isotropic conductor in a magnetic field can be described by the vector equation E=ρ⊥j+n(j·n) (ρ∥−ρ⊥)+ρH(n×j),relating the electric field E to the current density j. The resistivities ρ∥ and ρ⊥ are those which result when the magnetic induction is parallel to j, and normal to j, respectively; ρH is the Hall resistivity. The vector n is a unit vector which has the direction of the induction. When j is directed along the x axis, and n is made to rotate in the x-y plane with angular frequency ω, one obtains an electric field with ac components Ẽx=12jx(ρ∥−ρ⊥) cos2ωt,Ẽy=12jx(ρ∥−ρ⊥) sin2ωt.These equations describe the magnetoresistive effects in a rotating magnetic field. On the other hand, if n is allowed to rotate in the x-z plane, the y component of the electric field becomes Ẽy=ρHjxsinωt. This equation describes the Hall effect in a rotating field. By measuring the ac components of E having frequencies ω and 2ω when jx is known, ρ∥−ρ⊥ and ρH can be determined.
This rotating-field technique is being used to study the galvanomagnetic properties of ferromagnetic films of rectangular geometry. The films are placed in the field of a magnet rotating at a frequency of 20 cps. When the magnetic field is in the plane of the film, the magnetoresistive equations apply, as has been verified by measuring Ẽx and Ẽy using a wave analyzer. No components having a frequency other than 2ω (40 cps) were detected. The absence of a component with frequency ω shows that no ``Umkehreffekt'' is present in the magnetoresistance. If the wave analyzer is replaced by a high-gain amplifier having a narrow band-pass at 40 cps, it is possible to detect a magnetoresistive change (ρ∥−ρ⊥)/ρ∥=10−6 in a typical film of 10-Ω resistance. A particular advantage of this method is that it is not susceptible to small variations in ρ∥ or ρ⊥ due to fluctuations in temperature. Thus, measurements as a function of temperature are easily and rapidly obtainable.
The utility of the technique is demonstrated by measurements of ρ∥−ρ⊥ as a function of composition in Ni-Fe alloy films having fcc and bcc structures near 30% Ni. The effect of allotropic transformations (fcc→bcc) on magnetoresistance in these films is also presented. It has been found that this transformation occurs with greater difficulty in films on glass substrates than in the bulk alloys.
Low Flux Density Ferrite Memory Cores
Authors: Weisz R. S. , Brown D. L. 
Published: April 2005

Previously it has been shown that lowering the flux density Bs of ferrite memory cores has useful effects. Since hysteresis losses are proportional to Bs, lowered Bs allows higher repetition rates to be applied without deterioration of square-loop properties. Lowered Bs also contributes to lower delta noise Δ2, which is an important factor limiting the practical size of a coincident-current core array. The chief problem encountered in preparing low Bs materials is in simultaneously maintaining adequate squareness of the hysteresis loop, low coercivity, and high Curie temperature Tc.
A new series of materials is reported in which tin or indium substitutes for a portion of the iron in conventional magnesium manganese ferrites. For example, the composition 70 MgFe2O4·15 Mg2SnO4·15 Mn3O4 has Bs = 800 G, or approximately ⅓ that of usual square-loop ferrites. Typical 30-mils o.d. cores of this composition switched with a full drive of 580 mA at a risetime of 0.1 μsec have uV1 = 33 mV, dVz = 4 mV, Δ2 = 0.3 mV, tp = 0.18 μsec, ts = 0.37 μsec, IB = 350 mA, and Tc = 160°C. The Δ2 is less than half that produced by conventional ferrite memory cores switching at the same speed.
Ferrite Films Prepared by Pyrohydrolytic Deposition
Authors: Gleason F. R. , Watson L. R. 
Published: April 2005

Ferrite films of a nickel-zinc-cobalt composition have been deposited by pyrolytic hydrolysis of metal inorganic salts. The object of the research described in this paper was to deposit these films with a composition like that of a bulk ferrite of particular magnetic properties, and to evaluate the films in terms of structure, composition, and magnetic properties.
The films are prepared by atomizing a mixed solution of the metal chlorides into a reaction tube heated to 800°C. The metal ion concentration in the starting solution is compensated to allow for excessive and varying loss of the constituents during the film-forming process. The method used for determining the amount of starting solution compensation will be discussed along with a detailed description of the experimental apparatus.
The films prepared by this technique exhibit the ferrite spinel structure, as is evidenced by x-ray diffraction data.
A value of 100 for the initial permeability of the films was measured by observing the film B-H relationship. A study of film density and porosity was made from photomicrographs of the film cross section and from the weight of film deposited. These properties were compared to those of the bulk ferrite of like composition, and similar values were obtained.
Interactions in Various Magnetic Compounds
Authors: Gorter E. W. 
Published: April 2005

Susceptibility measurements on single crystals of KFe11O17 show an anomalous antiferromagnetic behavior, which we propose to call antiferrimagnetism. The behavior follows from Weiss field theory on a simplified (i.e., two-sublattice) model.
The magnetic structure of K2NiF4 has been determined by neutron diffraction by Legrand and Plumier at C.E.N., Mol (Belgium). Measurements on their single crystal show that χ∥ and χ⊥ become nearly equal at ≈100°K, i.e., far below the temperature where χ is maximum. This is believed to be due to a gradual breaking up of the long-range order in the basal layers. Results obtained on powders of La0.5Sr1.5MnO4 and La1.5Sr0.5CoO4 are also given.
Pure polycrystalline samples of EuS, EuSe, and EuTe with rocksalt structure show θ values of +16, +6, and −7°K; EuTe has a Néel temperature at +11°K. The ferromagnetism of EuO, EuS, and EuSe is due to a predominant direct positive exchange interaction Eu-Eu, the antiferromagnetism of EuTe to a predominant next-nearest neighbor superexchange interaction Eu-X-Eu. Neither interaction is believed to change sign in the series. Measurements of M vs T at various field strengths are in very good agreement with Weiss field theory.
Oxidic spinels with diamagnetic ions in A sites have so far shown negative θ values. The substances Ge[Fe2]O4, Ge[Co2]O4, and Ge[Ni2]O4 have θ values of −15, +90, and 0°K, respectively. The materials Ge[Ni2−2δLiδFeδIII]O4 have positive θ values, increasing linearly with δ to 180°K for δ=0.5. Here the Ni2+–Fe3+ interaction must be positive and this interaction is thought to be a direct one, as is discussed.
Study of Magnetoelastic Interactions by Parallel Pumping
Authors: Olson Frank A. 
Published: April 2005

Magnetoelastic interactions, the coupling of spin waves with phonons, have been studied in single crystals of yttrium iron garnet using the parallel pumping technique. Observations of the coupling have been made for various temperatures and crystalline orientations at 4.75 and 11.6 kMc.
An increase in the threshold field for spin-wave excitation occurs when there is magnetoelastic coupling, and the form of the increase provides a line shape for the spin-wave-phonon interaction. From the magnitude, width, and location of the interaction line are found the acoustic Q, the magnetoelastic constant b2, and the spin-wave exchange constant. The quantities obtained (i.e., Q=2×104 and b2=4.7×106 ergs/cm3 at room temperature) are in reasonable agreement with those from lower frequency measurements, assuming a f−1 variation for Q. The magnetoelastic constant b2 is found to increase with decreasing temperature. Correlation of the temperature variation of b2 with theoretical predictions is good and, if the comparison is valid, provides an evaluation of the higher-order magnetoelastic constant b5.
Magnetoelastic Coupling Constants of Terbium and Europium Iron Garnets
Authors: LeCraw R. C. , Kasuya T. 
Published: April 2005

The purpose of this paper is twofold: (1) to present data on the magnetoelastic constants of rare-earth iron garnets, a subject which for various reasons has been little studied thus far, and (2) to describe a new method for obtaining these constants which is applicable to many ferromagnetic insulators and does not require the use of strain gauges. The new method was developed from a study of the coupling introduced between long wavelength acoustic modes and long wavelength spin-wave modes by ions in which the orbital moment is not quenched, such as rare-earth ions, Co2+, and Fe2+. The effect of the coupling caused by such ions is observed as a magnetic field dependence of the resonant frequency of an acoustic resonator made from the given material, even above dc saturation. The acoustic Q above dc saturation is also field-dependent. A theory has been obtained which explains the observed field dependences of both v(H) and Q(H) as well as other important features of the magnetoacoustic interaction. It will appear elsewhere.1
One of the results of this theory is a relation between the cubic magnetoelastic constants, B1 and B2, and the acoustic resonant frequency v of a thin disk vibrating in a thickness shear mode. For a (110) disk with the external field H0 in the plane along [100] and the rf driving field perpendicular to the disk, we obtain ν=ν∞(1−B222c44MHeff),where Heff=H0+Hanis+4πM, and c44 is the usual shear elastic modulus, which may be obtained directly from v∞ and the thickness of the disk. Equation (1) applies to the mode with displacement along [100]. B1 is obtained similarly, only now H0 is along [110] in the plane, and the shear displacement is along [110]. Here we have ν=ν∞(1−B122c44MHeff). All data thus far have given excellent fits to these equations as Heff is varied, making it easy to obtain the unknown constants. It should be noted that Eqs. (1) and (2) are high-temperature approximations and at low temperatures will not in general be as simple.
For TbIG and EuIG at room temperature we find the following (all in ergs cm−3): For TbIG, |B1|≤3.5×106, |B2|=30×106; and for EuIG, |B1|=45×106 and |B2|≤4.2×106. The signs must still be determined from strain gauge measurements. The observed reversal of the magnetoelastic anisotropy (ratio of B1 to B2) is being investigated, as well as the temperature dependences of B1 and B2.
Irradiation of Magnetic Materials with 1.5- and 4-MeV Protons
Authors: Sery R. S. , Gordon D. I. 
Published: April 2005

Pure iron and 5% molybdenum Permalloy samples, 0.01 in. thick, were irradiated with 1.5- and 4-MeV protons at total incident integrated fluxes of 1016 and 1017 protons per cm2. The actual shapes used were a ring 1 31 6−in. o.d.×⅝-in. i.d. and a disk of ⅝-in. diameter. The ring was utilized for dc magnetic property measurements (before and after irradiation) while the disk was used for magnetic anisotropy torque measurements.
The remanence (Br) and maximum permeability (μm) of molybdenum Permalloy decreased by about 35%. This is of the same order of change produced by neutron irradiation of 1017 neutrons/cm2 in this material. However, measurements to date indicate that changes in coercive force and initial permeability due to proton irradiation are relatively small as compared with neutron irradiation effects. The decreases in Br and μm of the pure iron samples were of the order of 10 to 20% for irradiations of both ∼1016 and ∼1017 protons/cm2.
Both materials were essentially isotropic initially. Post irradiation torque measurements showed that the materials became slightly more isotropic. No changes were observed in saturation magnetization.
Heating of control samples to 250°C did not produce changes in magnetic properties, showing that temperature alone is not a factor in producing the permanent changes which occurred under irradiation. All irradiations were performed at temperatures below 250°C. The changes due to proton irradiation are thought to be due to proton-induced disordering.