bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Test of Viscous Dislocation Damping Theory
Authors: Fiore Nicholas F. 
Published: April 2005

The amplitude-independent dislocation damping of a series of dilute copper-germanium single crystals has been studied as a function of composition and frequency. The measurements have been performed at room temperature on annealed and γ-irradiated single crystals driven in longitudinal resonance at 80 and 240 kc/sec by means of the Marx piezoelectric oscillator.
The results indicate that the Granato-Lücke viscous damping analysis cannot account for the observed magnitude and composition dependence of the damping, although the damping is proportional to frequency in agreement with their theory. They further show that a γ-ray dose of 2×108 rad is sufficient to suppress the damping to a composition-independent value of 1×10−4 which does not decrease with further irradiation. There is evidence that the total damping consists of a composition-dependent edge dislocation loss superposed on a composition-independent screw dislocation loss.
Field Distribution in a Hard Superconductor with Adiabatic Field Change
Authors: Gauster W. F. , Ullmaier H. A. 
Published: April 2005

Wipf and Lubell have investigated flux jumping in Nb-25%Zr under nearly adiabatic conditions.1 They considered a semi-infinite slab for the purpose of calculating a critical value of the external field under the condition that this value is reached before the magnetic wave front hits a boundary of the superconductor. These calculations hold approximately for solid cylinders with large diameters and agree well with experimental results.
We have extended Wipf and Lubell's calculations to solid and hollow cylinders of arbitrary radii. The shape of the penetrating magnetic wave has been computed. The boundaries of the superconductors are taken fully into account. As might be expected, the data with hollow cylinders deviate very appreciably from those obtained with solid cylinders. In the case of a semi-infinite superconducting slab the critical field depends only on the specific heat function of the superconductor. In our more general case, however, the critical field is affected also by the dependence of the critical current density upon the local values of the magnetic field and the temperature. Experiments on solid and hollow cylinders of NbZr and Nb3Sn verify these calculations.
Effects of Ferromagnetism and Local Order on Electrical Resistivity of Au-Fe Alloys
Authors: Sundahl R. C. , Chen T. , Sivertsen J. M. , Sato Y. 
Published: April 2005

The electrical resistivity of a series of Au-Fe solid solutions, from 4.53 to 40 at. % Fe, has been measured from 1.50° to 350°K. Measurements were made on foils which had been (Q) quenched from 900°C and (A) quenched and subsequently aged at 75°C for 1 week. Results indicate that (1) the general shape of the ρ(T) curves can be explained by a spin-disorder scattering model for ferromagnetic alloys, (2) changes in the ρ(T) curves on aging are similar to those found in the magnetization and Curie temperature, and (3) alloys of less than 10% Fe exhibit a transition at temperatures similar to those found from Mössbauer measurements.
The residual resistivity ρ0 of these alloys goes through a maximum at 12% Fe and decreases for larger concentrations, indicating that all spins are not ferromagnetically ordered. This spin-disorder contribution to ρ0 decreases when the quenched alloy is aged at 75°C.
Dependence of the Magnetic Properties of Y3Fe5−xGaxO12 and Y3Fe5−xAlxO12 on Thermal History
Authors: Leo D. C. , Lepore D. A. , Nielsen J. W. 
Published: April 2005

The saturation magnetization, Curie temperature, compensation point, and ferromagnetic resonance linewidth of Y3Fe5−xMxO12, M=Ga or Al, depend upon the thermal history of the sample. For example, a single crystal of YGaIG, x=1.26, will exhibit a room-temperature 4πMs between 220 and 88 G as it is quenched from temperatures ranging downward from 1275°C and finally slow-cooled to room temperature. Tc will decrease 3.5°C. The results can be explained by assuming the Ga or Al concentration on octahedral sites increases with increasing temperature. The direction of the change in Curie temperature is predicted by Gilleo's theory.
The results are important to the control of magnetic properties of garnets in applications requiring closely matched samples.
Some Measurements of Inhomogeneous Permanent Magnets by the Pole-Coil Method
Authors: Steingroever E. 
Published: April 2005

The pole-coil method for measuring demagnetization curves of permanent magnets is applied to inhomogeneous magnets. It allows the analysis of different causes of inhomogeneities: differences in the intrinsic magnetic properties within one test sample, in the degree of orientation of otherwise homogeneous material, in the effectiveness of magnetic heat and annealing treatment; inclusion of holes or nonmagnetic contaminations; unequal cross sections of the tested magnet, e.g., with conical shape.
By the pole-coil method inhomogeneities can be recognized by differences in remanence and coercivity. But in the case of serial arrangement of different components the resulting coercivity of an inhomogeneous sample is an average value of the coercivities of the components and nearly unaffected by the location of the measuring spot. The measurement of a magnet with different cross-sectional areas on both faces yields data for immediate magnetic circuit design.
Considerations in the Design of Permanent Magnets for Use with Microwave Tubes
Authors: Underhill Earl M. 
Published: April 2005

The use of ``microwave magnets'' dates, in this country, from about 1939, when the first Alnico magnets were made for magnetron tubes. Permanent magnets for this application usually involve more engineering and encounter more production problems than any other usage. All crossed-field tubes and all tubes using a magnetic field to focus a beam of electrons depend for their operation on the basic reaction between a moving charge and a magnetic field: F=ev×B, essentially the motor reaction. The electrical efficiencies of all electromagnetic, dynamic devices depend, in a complicated fashion, upon the magnetic energy density within the interaction volume. This underlies the fundamental design problem connected with microwave tube magnets.
The solution of this problem sometimes requires special design techniques, and normally demands much in the way of special manufacturing equipment and procedures. Because of the large magnets usually involved, maximum stored energy is important, but maximum stored energy per dollar of purchaser's over-all cost remains paramount. High energy combined with high operating field strength is important for magnets to be used for focusing.
The newer columnar grades of Alnico, of both medium and high coercivity, offer excellent opportunities for improved tube designs, and for an expansion of applications not yet predictable. These alloys, however, have introduced many new problems related to their manufacture and control of quality, not all of which have, as yet, been completely resolved. It is important that the design of any microwave magnet be carefully integrated with that of all the other components of a tube.
New Texture in Iron and Iron Base Alloys
Authors: Aspden R. G. , Berger J. A. , Trout H. E. 
Published: April 2005

The observation of a new orientation in iron and iron base alloy sheets is reported. This texture is prepared by annealing iron and iron base alloys, characterized by a gamma to alpha transformation, in the gamma region and slowly cooling through the phase change. The new texture is {001} 〈uvw〉. The occurrence of this structure is documented with the use of etch pits, domain patterns, and an x-ray method.
The magnetic characteristics for iron sheet with the {001} 〈uvw〉 texture are compared with those of iron sheet with a weakly oriented texture resulting from primary recrystallization and normal grain growth. Iron sheet with this new texture is easier to magnetize and has lower losses. The improved magnetic characteristics are ascribed to the elimination of grains having a hard direction of magnetization in the surface of the sheet. Iron and iron base alloys with this texture should find application in rotating electrical equipment.
Application of Soft Magnetic Materials and Specialty Alloys
Authors: Olson R. D. 
Published: April 2005

Many advancements recorded by the electrical and electronic industries in the past two decades can be directly attributed to advancements in magnetic materials technology. Efficiencies of power generation and conversion systems have improved through the development of lower energy loss and grain-oriented magnetic alloys. Control systems have become smaller and lighter due to improved flux-carrying capabilities of static magnetic components.
Requirements placed on magnetic materials by the military and space efforts have been ably met by existing materials. Elevated temperature data are presented showing magnetic design data for temperatures to 1400°F. Examination of these data and elevated temperature mechanical data indicate where advances in materials technology are needed.
Two factors are significant in the processing of materials into components. These are: correlation of basic material parameters to device performance and the effects of processing various magnetic geometries on basic material characteristics. Technological improvements in these areas offer further gains for control and power systems.
Future demands on magnetic materials to meet the growing needs of the electrical and electronic industries dictate that a higher degree of sophistication will be required in alloy design, material fabrication, apparatus design, and materials processing.
Some Properties of an Anisotropic Thin-Film-Waffle-Iron Memory Cell
Authors: Bobeck A. H. , Perneski A. J. , Reekstin J. P. 
Published: April 2005

A new mode of operation of the cubic waffle-iron memory cell in which an anisotropic, rather than isotropic, storage film is used has been investigated. When a conventional 1000-Å NiFe film is combined with a high-permeability ferrite baseplate a high-speed, low-current device is obtained. Typical operating parameters using a waffle baseplate containing 0.005-in. slots on 0.015-in. centers are:Iword=90 mA, Idigit=10 mA, Vsignal=1 mV, and a creep threshold of 5 mA.
A number of 1000-Å NiFe films have been evaluated in both a continuous and a discrete shape configuration. It was found that the allowable skew for a particular film may be increased if bipolar rather than unipolar word currents are used.
Because of the complex nature of the field patterns in the waffle-iron structure it was necessary to supplement the standard operational pulse tests with direct domain observations using the Kerr magneto-optic effect.
The observed domain patterns were completely unexpected. Study of these patterns disclosed large range flux spreading along the easy-direction axis of the film. This spreading of flux, called the ``domino effect'' has been exploited in a remotely sensed memory cell. Output signals completely free from the usual digit current couplings have been obtained.
Saturable Shielding-A Technique for Nonlinear Coupling in Magnetic Circuits
Authors: Berger R. , Crowther T. S. , Raffel J. I. 
Published: April 2005

If a magnetic film (the shield) with transverse saturation demagnetizing field Hd and anisotropy field Hk is placed in a transverse field below saturation strength (Hd+Hk), it experiences a net field less than Hk. A second film (the storage film), when placed on top of the first, will experience the same net field. If the anisotropy field of the storage film is much greater than that of the shield, the magnetization of the storage film undergoes a negligible rotation for all applied fields below Hd+Hk. Once the shield has saturated, any further increase in field is applied directly to storage film. The resulting plot of the net field at the storage film versus applied field shows a symmetrical offset threshold of approximate magnitude Hd. Control of the shield geometry provides a means for adjusting this threshold.
To investigate the shielding effect, two experiments were performed. The first used a 0.5-in.-wide Supermalloy tape to approximate an ideal shield and measured net field at its center line as a function of field applied with Helmholtz coils at very low frequencies. The second sought to demonstrate the practicality of shielding in a film memory. Both shield and storage medium were thin films of 0.004-in. width driven by pulsed word and digit fields using a technique which eliminated the readout from the shield. The results of both experiments show agreement with the theoretical models proposed in the paper.
Possible applications of the shielding technique are to all-magnetic selection in film memories and to creep reduction in conventional word-organized film memories.
Ferromagnetism in CdCr2Se4 and CdCr2S4
Authors: Menyuk N. , Dwight K. , Arnott R. J. , Wold A. 
Published: April 2005

A study has been made of the magnetic properties of the spinels ACr2X4, where A is diamagnetic zinc or cadmium, and X is oxygen, sulfur, or selenium. CdCr2Se4 and CdCr2S4 are apparently ferromagnetic with moments somewhat below the predicted value of 6.0 μB/molecule. By contrast, ZnCr2Se4 and ZnCr2S4 are antiferromagnetic at low temperature despite having positive asymptotic Curie points (TA). We found very little thermal variation of cell size in these materials, which further corroborates Lotgering's conclusion that the antiferromagnetism is due to next-nearest-neighbor interactions.
Disagreement between experimental values of TA/TC and the theoretical value calculated assuming nearest-neighbor interactions indicate that next-nearest-neighbor interactions are playing a role in the ferromagnetic materials as well.
Comparisons of TA and TN in these materials indicate that the magnetic interactions are strongly dependent upon the diamagnetic A-site ion. However, the data cannot uniquely attribute this effect to an exchange coupling directly involving the A-site cation.
Magnetic Structure of Ga2−xFexO3
Authors: Frankel R. B. , Blum N. A. , Foner S. , Freeman A. J. , Schieber M. 
Published: April 2005

High-magnetic-field-Mössbauer and magnetic-moment experiments have been performed with Ga2−xFexO3. This magnetic system is of considerable interest because it is piezoelectric, weakly magnetic,1 and magnetoelectric.2 The crystal structure has been determined3 and a magnetic ordering inferred.3 The magnetic-moment measurements were made using a vibrating sample magnetometer in fields up to 75 kOe. The samples used for the Mössbauer absorption experiments consisted of 57Fe enriched powders, grown from a flux, embedded in lucite, and having x=0.8 and 1.2. A mosaic absorber made of small x-ray oriented single crystals was also studied. Measurements were made over the temperature range 4.2° to 320°K and in external magnetic fields up to 130 kOe. At low temperatures the zero-external field-absorption spectra indicate that there are at least two magnetically nonequivalent sites. In a large external field the hyperfine spectrum lines corresponding to Δm=0 vanish, while each of the outer lines (corresponding to Δm=±1) splits into two well-resolved components of unequal intensity. Detailed analysis of the experimental results for both the single crystal and polycrystalline absorbers indicates that at zero external field all spins lie in the a−c plane (c&lt;a&lt;b), that the observed moment is due to ferrimagnetism4 rather than to a canted spin structure, and that the spins are unequally divided between the two sublattices.
A detailed account of these measurements will be published elsewhere.
Unidirectional Anisotropy in Multilayer Films of Cr and NiFe
Authors: Sharp R. W. , Archibald P. C. 
Published: April 2005

Layered films of Cr and NiFe alloy have been made which exhibit biased hysteresis loops in the easy direction and asymmetric hysteresis loops in the hard direction. The asymmetry in the hard direction is reversed by rotating the film a few degrees in the loop tester. The magnitude of the bias is 0.5 Oe for films consisting of a 500-Å layer of 76% NiFe on top of a 500-Å layer of Cr on a soft glass substrate.
No loop bias was observed for films of 82% NiFe, for films on hard glass substrates, or for films with layer thicknesses departing from 500 Å by a factor of two.
The films exhibit high sensitivity to externally applied stress. Loop bias can be eliminated by raising the temperature above the Néel point of Cr. The unidirectional axis is a function of the direction of a magnetic field applied during cooling of a film through the Néel point.
The observed phenomena are believed due to exchange anisotropy between antiferromagnetic (strain sensitive) Cr and ferromagnetic NiFe. Crystal anisotropy, shape anisotropy, magnetostriction, etc. are not unidirectional. The only unidirectional effects reported in the literature have resulted from exchange anisotropy.
Sensitive Pulsed Magnetoresistive Measurement of Magnetic Film Hk
Authors: Johnston R. C. 
Published: April 2005

For a magnetic annealing experiment with Permalloy films it was necessary to measure the uniaxial anisotropy field Hk without breaking vacuum after deposition, while maintaining a transverse field H⊥≳Hk. The annealing mechanism could then be studied as a function of temperature by a plot of Hk vs time. In the presence of the field H⊥, longitudinal ac (500 cps) field H∥«Hk, and longitudinal dc film current, a second harmonic magnetoresistance signal is generated. The measurement is based on the phase reversal of this signal when H⊥ = Hk. Rather than sample only one cycle of the 2nd harmonic output, 30 cycles are used and averaged in an integrator. The transverse field consists of a dc bias and a 1-cps triangular or sinusoidal waveform. The minimum resultant field is maintained at Hk by means of negative feedback to the dc bias. Typical system performance is as follows: For an Hk of 5 Oe, ΔHk is readable to 0.01 Oe or 0.2%. Absolute value of Hk is measured to about 5% accuracy. The system will follow changes at a maximum rate of 0.2 Oe/sec.
A second-generation system will also be described which uses simpler electronics and is more flexible with regard to the annealing and sensing directions of the film.
Magnetic Structures in CrTe—CrSb Solid Solutions
Authors: Takei W. J. , Cox D. E. , Shirane G. 
Published: April 2005

Neutron diffraction studies have been made of solid solutions of ferromagnetic CrTe and antiferromagnetic CrSb which crystallize in the hexagonal NiAs structure. Similarities are found with the isostructural system MnSb-CrSb, in which good agreement is obtained with de Gennes predictions for the effects of double exchange on an antiferromagnetic system. The most striking feature is the formation of a canted spin structure with cosine of the cant angle varying as a linear function of composition. The variation of angles and transition points when analyzed in terms of double exchange theory gives about the same value of b/|J| S2 in the two systems. At very high CrTe contents, a different type of canted spin structure occurs.
The possibility of deviations from the ideal structure as can occur in CrTe is examined. A least-squares structure analysis was made which indicated the absence of distortions in most of the solid solutions.
Skin Effect in Anisotropic Plasmas and Resonance Excitation of Electron-Cyclotron Waves. I. Theory
Authors: Pfeiffer B. 
Published: April 2005

The complete electromagnetic field has been calculated within a homogeneous infinite two-dimensional plasma sheath with a perpendicularly applied static magnetic field. The plasma is produced by a high-frequency electromagnetic field at the surface. When the electron-cyclotron frequency is greater than the frequency of the applied high-frequency electromagnetic field at the surface, the refractive index of the medium becomes real for the right-hand polarized wave and one has an increased penetration of high-frequency energy into the interior of the plasma.
It is also possible for the refractive index to reach a value such that the thickness of the plasma sheath is half a wavelength. In this case, resonance effects should be expected for the electron-cyclotron wave which propagates in the plasma.
Kinetics of Coarsening of Spherical Particles in a Liquid Matrix
Authors: Sarian S. , Weart H. W. 
Published: April 2005

The theory of particle coarsening kinetics under control by diffusion through the matrix and by phase-boundary reaction is reviewed, and extended to the case of diffusion control when the particles are closely spaced and for impurity control at the interface. For the first case, d̄=f(T,φ)t⅓, Nv=f(T,φ)t−1, where d̄ is the mean particle diameter, φ is the volume fraction solid, T is temperature, and Nv is the number of particles per unit volume. For the latter two cases, d̄=f(T)t12,Nv=f(T)t−32, the temperature-dependent functions being different for the two cases.
The models are used to discuss existing kinetic data on the iron-liquid copper and oxide-liquid silicate systems. New data on the NbC-liquid iron system reveal the absence of the expected diffusion-field interaction effect when particles are close together. The role of surface-active impurities, particularly boron, on the mechanism of growth is discussed and it is shown that, while growth may be diffusion-controlled in the absence of impurities, it may become phase-boundary reaction controlled when appreciable quantities of impurities are present. The apparent coefficient of diffusion of iron in copper is calculated to be about 6.06×10−4 cm2/sec at 1120°C.
Dynamic Friction Measurements on Belts of Viscoelastic Materials
Authors: Cunningham R. G. 
Published: April 2005

The frictional behavior of belts of viscoelastic materials slipping on metal rollers has been investigated as a function of the amount of slip. The results show that the exponent in the relation Ff/A = a(Fn/A)x, relating frictional force per unit area to normal pressure, was greater than unity at low values of slip. This may be due to a height distribution of microscopic asperities on the surfaces.
The value of the exponent generally decreased as the slip increased. This can be explained by assuming that the deformational response of the viscoelastic material becomes more elastic as the slip is increased. A corresponding increase in the proportionality constant can be accounted for if the shear strength of these materials increased at a faster rate than the stress-strain proportionality constant as the slip was increased.
Diffusion of Lithium into Ge and Si
Authors: Pratt B. , Friedman F. 
Published: April 2005

Lithium was diffused into Ge and Si at temperatures 300°−400°C and 400°−500°C, respectively. The diffusion was carried out in an inert gas atmosphere by decomposing LiAlH4. The concentration of Li impurities as a function of depth from the surface of the sample was determined by lapping down thin layers of the diffused part of the sample and measuring the conductance of each of these thin layers. An erfc was chosen to fit the experimentally measured concentration curve from which the diffusion constant D for each temperature of diffusion was determined. The following dependence of temperature was found: D=9.10×10−3exp(−13100/RT) for Ge,and D=2.65×10−3exp(−14500/RT) for Si,where D is measured in cm2/sec, T in °K, and R=1.98 cal/°K.
The deviation in the experimental values of D was not more than ±10% for Ge and ±20% for Si.