bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alpha-Sub-Gamma Phase in Alnico 8 Alloys
Authors: Julien C. A. , Jones F. G. 
Published: April 2005

The kinetics of formation at 900°C of the fcc γ phase have been studied metallographically in Alnico 8 alloys with Cu contents from 0.01 to 3.34 at. %. Increasing Cu content is found to increase the gamma-forming tendency. Selected two-phase specimens subjected to electron microprobe analysis showed a systematic depletion of the matrix in Cu, usually accompanied by an enrichment in Co. Ti evidences some partitioning, but scatter prohibits a reliable interpretation. Other elements apparently do not partition during the formation of γ. But in a specimen held for 24 h (i.e., beyond the growth stage), a third phase appears, accompanied by definite shifts in partitioning.
Deterioration of permanent magnet properties (but not 4πIs) as the transformation proceeds is described. The Br decrease is nonlinear, and it appears that interaction between the matrix and second phase is required to account for the observed property effects.
Influence of Static Pressure on the Coercive Force of Barium Ferrite Powder
Authors: Tenzer Rudolf K. 
Published: April 2005

In recent studies of ferrite powders, changes of the intrinsic coercive force (Hci) have been ascribed to:(1) lattice defects, and (2) particle size reduction which occurs during milling. In order to test the two interpretations, the Hci of barium ferrite powder (ball milled to particle sizes of about 0.02–0.5 μ) was measured under static pressure. The coercive force increased with increasing pressure, reached a maximum at 8000 psi, and then decreased.
To interpret this result on the basis of dislocations would require that the dislocation density be lowered as the pressure is increased, which is unlikely. On the other hand, this behavior is easily understood on the basis of an increase of the effective particle size due to more contact between the particles at higher pressure. According to the latter interpretation, increasing pressure reduces the effect of thermal fluctuations, thus increasing the coercive force. At pressures above 8000 psi, multidomain behavior becomes a predominant factor in lowering the Hci. This interpretation is supported by the following experimental facts: below 8000 psi the coercive force decreased when the pressure was released. Above 8000 psi, however, the coercive force increased after the pressure was released.
These experiments show that particle size and exchange interactions between the particles are major factors in determining the coercive force of barium ferrite powders.
Secondary Recrystallization and Its Relation to Magnetic Properties in Thin Grain-Oriented 3% Silicon-Iron
Authors: Littmann M. F. 
Published: April 2005

Polycrystalline 3% silicon-iron with (110)[001] texture forms a primary recrystallization texture near the original texture after cold reduction of about 70% followed by primary recrystallization. If rapid heating is used for primary recrystallization, vigorous secondary recrystallization by grain boundary energy takes place after subsequent annealing at 775°C. The secondaries grow to about 5-mm diam with a texture deviating from the primary texture. Annealing twins also form during secondary growth. The activation energy for this growth was found to be much lower than for growth processes dependent on impurities for inhibitors. Such secondary growth must be avoided in commercial applications.
If primary recrystallized material is annealed at 1200°C under conditions favorable for growth of (100) by surface energy, (100)[001] secondaries will grow depending on the amount of prior cold reduction.
Magnetic Aftereffects in Neutron-Irradiated Iron, Nickel, and Cobalt
Authors: Moser P. , Peretto P. , Dautreppe D. , Vigier P. 
Published: April 2005

After neutron irradiation of iron at 78°K, we have observed four magnetic aftereffect zones. All these zones annealed out in different temperature ranges corresponding to the well-known stages of recovery in neutron-irradiated iron. If the sample is annealed during 30 min at 500°C after an irradiation at 78°K, a new magnetic aftereffect zone appears. The different characteristics of each zone (activation energy for reorientation, spectrum width, defects symmetry, etc.) have been studied. A model concerning the nature of the defects responsible for these magnetic aftereffects is proposed.
Similar effects have been found in neutron-irradiated nickel and cobalt at 28°K. From the results on nickel a great number of arguments are given in favor of the interstitialcy configuration.
Paramagnetic Faraday Rotation of EuSe
Authors: Suits J. C. , Argyle B. E. 
Published: April 2005

Faraday rotation and absorption measurements were made on a bulk single crystal and on evaporated polycrystalline films of EuSe. Bulk EuSe is ferromagnetic, transparent in the red, and exhibits an unusually large Verdet constant at room temperature: −9.7 min/Oe-cm at 6660 Å where the absorption is 173 cm−1. Measurements at 77°K show that the Verdet constant varies approximately inversely with temperature and thereby correlates with the magnetic susceptibility. These properties are due to the Eu+ + ion and are comparable to those we have observed in other divalent europium compounds such as Eu2SiO4.
The evaporated films of EuSe exhibit a broad but well-defined absorption band at 4600 Å which is essentially duplicated in similarly prepared films of EuS and EuO at 5200 and 5800 Å, respectively. The wavelength dependence of the Faraday rotation of EuSe exhibits a rather complicated structure with two sign reversals in the region of the absorption band. At 6660 Å the Verdet constant measured at room temperature is −6.3 min/Oe-cm agreeing in sign and approximately in magnitude with the bulk value, whereas the maximum value of Verdet constant, +25 min/Oe-cm, occurs at 4330 Å.
Magnetization, Resonance, and Optical Properties of the Ferromagnet CrI3
Authors: Dillon J. F. , Olson C. E. 
Published: April 2005

CrI3, noteworthy as one of the few insulating ferromagnets, is one of a series of presumably isomorphous compounds (CrCl3, CrBr3, and CrI3) which show similar or closely related magnetic ordering. CrI3 samples containing some single crystals (plates a few square millimeters in area) were made by reacting chromium metal and iodine in a sealed quartz tube. Magnetization measurements of the powder were made by Williams and Sherwood at several fields up to 15 300 Oe over the range 1.5° to 300°K. In addition, M (H) was plotted at 4.2°K up to 70 000 Oe. The ferromagnetic Curie temperature is 68°K, and the paramagnetic Curie temperature is 70°K. The low-temperature saturation magnetization is 3.10 μB/Cr+ + +, corresponding to 4πM = 2690 G. The field for ferromagnetic resonance was measured at 86, 91, and 99 Gc/sec. The spectroscopic splitting factor g = 2.07, and the anisotropy field 2K/M = 28.6 kOe at 1.5°K.
Optical transmission measurements on CrI3 single crystals showed a very strong absorption band down to a band edge near 10 000 cm−1. The specific magnetic rotations associated with the band edge are almost as large as those observed in the tribromide. Evidence of domain diffraction was seen.
Hall and Faraday Effects in Oriented MnBi Films
Authors: Chen D. , Gondō Y. , Blue M. D. 
Published: April 2005

Hall coefficients and resistivity have been measured over the temperature range 77° to 300°K on polycrystalline MnBi films prepared with the c axis of the crystallites normal as well as parallel to the plane of the film. The Hall resistivity follows the well-known relation ρH = R0H+MR1, where R0 and R1 are the ordinary and extraordinary Hall coefficients and M is the magnetization. At room temperature, R0 is 6×10−3 cm3/C for both types of films and R1 is 7×10−2 and 2.5×10−1 cm3/C for the perpendicular and parallel films, respectively.
Measurements of the magneto-optic Faraday rotation of perpendicular films indicate that the Faraday rotation is directly proportional to the magnetization. Over the visible wavelength region, the Faraday rotation was found to increase as temperature decreases from 300° to 87°K, by a factor less than 25%. The specific rotation for a typical magnetically saturated film was 1.4×105 deg/cm at the 6328-Å He–Ne laser line at room temperature.
Our measurements are in agreement with Goodenough's suggestion of metallic conductivity resulting from a d band formed from the transition metal cations with the assistance of large numbers of interstitial cations. An effective hole density of 1021 cm−3 and Hall mobility of approximately 10 cm2/V-sec characterize these films.
Electroluminescence and Lasing Action in GaAsxP1−x
Authors: Pilkuhn M. , Rupprecht H. 
Published: April 2005

The electroluminescence of Zn diffused diodes was studied in forward and reverse bias. Emission spectra obtained for forward biasing showed a near-edge as well as a low-energy line. In the composition range x&gt;0.55, where the lowest conduction band minimum is at k=0, most photons are emitted in the near-edge line. Lasing action could be observed in this range, and the shortest wavelength where stimulated emission was obtained at 77°K was 6380 Å. For x&lt;0.55, where the lowest conduction band minimum is the (100) minimum, the low-energy emission becomes dominant. The energy separation between near-edge and low-energy line varies between 0.4 and 0.47 eV at 77°K depending on composition. This suggests that the same defect is responsible for the low-energy emission in all these diodes (including GaAs and GaP). In reverse bias, near-edge emission and emission at higher energies than bandgap could be observed for x&lt;0.55. The cutoff energy of the emission on the high-energy side was measured as a function of composition. It was found to vary in a manner similar to the variation of the energy of the (000) conduction band minimum.
The external quantum efficiency of the forward bias emission drops sharply by two orders of magnitude at the composition x=0.55 when x is decreased. The efficiency of the reverse bias emission is independent of composition.
Standing Spin Wave Mode Spectra in Thin Permalloy Films Prepared in Vacuum of 10−7 Torr
Authors: Nisenoff M. , Terhune R. W. 
Published: April 2005

The spacings between the standing spin wave modes excited in Permalloy films, prepared in a high-vacuum system at pressures near 10−7 Torr, are found to obey a quadratic dependence on order number for the magnetic field normal to the plane of the film (H⊥) as well as in the plane of the film (HII). The spacings and intensities of the modes, as a function of the angle φ which the magnetic field makes with respect to the film normal, indicate that the modes are nearly unpinned for φcrit&gt;φ≥90° (HII), are completely unpinned at φcrit, and partially pinned for φcrit&gt;φ≥0° (H⊥). This type of pinning behavior is explained qualitatively by assuming that the films are nearly uniformly magnetized except for a very thin surface layer, of the order of ten lattice spacings, which exhibits a lower magnetization than the bulk. In addition, the observed pinning for the modes suggests that the boundary condition imposed on the transverse component of the magnetization at an air-ferromagnetic interface is that the normal derivative of the magnetization vanish.
It is concluded that ferromagnetic films prepared in high vacuum should be suitable for the determination of physical parameters, such as A/M, the ratio of exchange constant to the saturation magnetization, as their spectra are relatively free from the anomalous features observed in all of the previously reported SSWM investigations. Experimental evidence is presented that these anomalous features are probably due to contamination of the films by both residual gases in the evaporation chamber and by impurities introduced by the vacuum system itself.
Evaluation of Kossel Microdiffraction Procedures: The Cubic Case
Authors: Gielen Paul , Yakowitz Harvey , Ganow DeWayne , Ogilvie Robert E. 
Published: April 2005

A complete theory of the lens-shaped intersection of Kossel lines in the transmission pseudo-Kossel method is developed. The general expression gives the lattice parameter with respect to the characteristics of the interaction of two arbitrary conics, i.e., conics corresponding to arbitrary diffracting planes and arbitrary wavelengths. Geometrical considerations involving the conics are developed and from these, the errors involved in lattice parameter measurement are evaluated. Lattice parameter variations of 10−5 can be easily measured with suitably chosen conic intersections. The precision to be expected as a function of measurement errors is expressed as a sensitivity ratio and tabulated for an Fe-3wt.%Si alloy. Several methods of reducing measured lengths to lattice parameter data are evaluated.
The IBM 7090 computer has been used to find suitable intersections for precise lattice parameter measurement. The computer supplies the wavelengths and conics to be used in the transmission pseudo-Kossel method. Consequently, a long and tedious experimental investigation is avoided. Examples using Fe-3wt.% Si are given; the lattice parameter for this alloy is found to be 2.86268±0.00003 Å. Proper radiations for investigation of Ge and diamond are indicated.
Axial Imperfections in Filamentary Crystals of Aluminum Nitride. I
Authors: Drum C. M. 
Published: April 2005

Axial dislocations and other imperfections in single-crystal whiskers of aluminum nitride (hexagonal, wurtzite structure) have been studied by transmission electron microscopy. Axial dislocations with c Burgers vectors and faults on the (101̄0) prismatic planes having fault vectors equal to ½ c have been identified. In addition to simple axial dislocations, the variety of axial imperfections included zig-zagged dislocations and wide periodic imperfections attributed to complicated faults, clearly related to the dislocation with a c Burgers vector.
One type of AlN whisker with growth direction 〈c+2a〉 always contained an axial dislocation or the related extended defect, and it is thus concluded that the growth of this type of whisker may have involved an axial dislocation.
Dilute Ferromagnetic Alloys
Authors: Crangle J. , Scott W. R. 
Published: April 2005

Long-range ferromagnetic coupling occurs in several dilute solid-solution alloys of the ferromagnetic transition elements in Pd or Pt. New measurements of magnetic moments and Curie temperatures of PdFe, PtFe, PtCo, and PdNi alloys are reported, and previous work on these and some of the more general properties of these alloys are briefly reviewed. Also, ferromagnetism occurs in dilute PdGd solid solutions.
Dilute solutions of iron in gold are ferromagnetic, although below about 10% of Fe there seems to be no homogeneous bulk ferromagnetism.
Ferromagnetic Dilute Alloys
Authors: Kanamori Junjiro 
Published: April 2005

In the first part an approximate method to treat the problem of one impurity atom in an otherwise pure metal is developed on the basis of tight-binding approximation. The method is capable of taking into account the degeneracy of the 3d bands and the mixing of the 3d bands with the 4s band. It is shown that one can treat each 3d atomic orbital of the impurity atom separately.
In the second part, dilute Ni alloys with other 3d transition metals are discussed on a simple model. The calculation substantiates Friedel's theory of these alloys. The negative magnetic moments of Cr and V in Fe are also discussed.
Relaxation and Nonlinear Effects in Ferromagnetic Thin Films
Authors: Berteaud André-Jean , Pascard Hubert 
Published: April 2005

In the first part, the authors give curves of ΔH versus the thickness d of the films magnetized normal and parallel to the film plane. One can see that ΔH⊥ (normal case) does not vary with d whereas ΔH∥ (parallel case) increases with d. Using the classical dispersion curves of degenerate spin waves, the authors conclude that internal imperfections are not responsible of the variations of ΔH∥ but it seems that the main source of scattering may be due to the edges of the films.
In the second part, the preliminary results of the behavior of thin films with high microwave power are given. The bulk sample theory of Suhl predicts that no subsidiary absorption is present. In the measurement of our films (f=9.3 GHz and 4πM = 104 Oe), the experimental curves exhibit a subsidiary absorption and a saturation of the uniform resonance mode, similar results being obtained with other samples. Finally, the authors give the variations of χ″/χ0″ with P/Pc and conclude that these curves can be used to obtain some information concerning the internal or surface imperfections of the films.
Electrical Properties of Inert Gas Plasmas Generated in Thermionic Cold-Cathode Diodes by Radiation in a Nuclear Reactor
Authors: Forman R. 
Published: April 2005

The electrical properties of inert gas (Xe, Kr, Ar) plasmas have been studied in a nuclear reactor environment at gamma radiation dose rates up to 6×108 rad/h. The measurements are made by inserting a gas-filled thermionic diode into the core of a 5-MW nuclear reactor. The space-charge neutralization effects caused by the ion-electron pairs generated in the gas are measured and interpreted in terms of plasma properties of the gas. The electrical conductivity of the plasma, at a constant radiation level, goes through a maximum as a function of pressure in the range of 1–300 Torr. If the radiation dosage is varied, keeping all other factors the same, one finds the electrical conductivity monotonically increases with dose rate in the range of 106−6×108 rad/h.
Experiments are described which indicate that electrons can be removed from a low work function ``cold'' electrode into the plasma by a mechanism different from either thermionic or field emission. A physical model is proposed to explain this phenomenon.
Surface-Energy Determinations by Cleavage
Authors: Gillis Peter P. 
Published: April 2005

An analysis is made of the strain-energy distribution in a slotted double-cantilever cleavage specimen. In this type of specimen the crack is medially constrained by a pair of longitudinal slots, so that surface energies can be determined in nonmonocrystalline samples.
The analysis treats the arms of the crack as end-loaded cantilever beams, and the post crack-tip region as a pair of elastically supported beams. The web produced by slotting is assumed to act as an elastic foundation for the remaining beam-like portions of the post crack-tip region. An expression for the specific surface energy of the material is then derived from conservation of energy at the instant the crack begins to propagate. Linear elastic behavior of the material is assumed and shearing strains are neglected.
Extension of the analysis to conventional (unslotted) specimens in which medial constraint of the crack is obtained through a preferred direction of cleavage, is discussed semiquantitatively in terms of an effective foundation modulus.
Low-Temperature Heat Capacity of Vitreous Germania
Authors: Antoniou A. A. , Morrison J. A. 
Published: April 2005

The heat capacity of a specimen of pure vitreous germania has been measured between 2.3° and 23°K. An ``excess'' heat capacity is found which is qualitatively similar to that of vitreous silica which has been widely discussed. However, in contrast to the example of vitreous silica, the heat capacity of vitreous germania at the lowest experimental temperatures is very close to that corresponding to the elastic constants.
In the region just above T = 0°K, the ``excess'' heat capacities of both vitreous silica and germania can be accounted for within about the experimental error by the occurrence of small peaks in the low-frequency part of the vibrational distribution. The ratio of the frequencies of the lowest peaks is about 3, which is very close to the ratio of the temperatures at which acoustic attenuation is observed in the two glasses. Nevertheless, a direct correlation between attenuation and ``excess'' heat capacity does not seem possible. The integrated relaxation strengths of the ultrasonic attenuation are nearly the same in the glasses but the numbers of low frequencies required to explain the initial ``excess'' heat capacities differ by a factor of about 50.
Creep in Vacuum of MgO Single Crystals and the Electric Field Effect
Authors: Rothwell W. S. , Neiman A. S. 
Published: April 2005

Experimental techniques are described and data are presented on bending creep of single-crystal MgO in vacuum from 800° to 1630°C. Evidence is discussed which supports the conclusion that creep near 1000°C is rate-controlled by cross-slip of screw dislocations with an activation energy of 1.5±0.25 eV. Creep above 1300°C takes place at a constant rate with an activation energy of 5.85±0.73 eV and a stress dependence exponent of 3. This creep is attributed to oxygen-ion diffusion-controlled climb of edge dislocations.
The effect of an electric field to give a transient acceleration of the creep rate is described. Experiments to define and characterize this effect are described and discussed.
Instantaneous Direct-Display System of Plasma Parameters by Means of Triple Probe
Authors: Chen Sin-Li , Sekiguchi T. 
Published: April 2005

A new electrostatic probe method utilizing the triple probe is proposed in which no voltage or frequency sweep (or switching) is required. This feature enables us to determine the instantaneous values of the electron temperature (Te), as well as the electron density (ne), within a short time which is of the order of the intrinsic response time of the probe itself (⪝1μsec). Moreover, the system allows the direct display of the Te values as well as the semidirect display of the ne values on appropriate display units, thus permitting us to eliminate almost all procedures usually required for data processing. In view of the features mentioned, this system may be a useful diagnostic tool not only for stationary plasmas but also for rapidly varying time-dependent plasmas of various types.
This paper presents theoretical considerations for the instantaneous direct-display system using a symmetrical triple probe. Discussions are also presented for the estimation of errors caused by the variation of ion saturation current, for the application to magnetoplasmas, and for the time and spatial resolutions. Experimental confirmation was made through the measurements of stationary magneto- as well as non-magnetoplasmas. As an example of the application to time-dependent plasmas, the electron temperature waves accompanied by the moving striations in hydrogen discharge were observed.
Plasma Microwave Interaction
Authors: Keržar B. , Weissglas P. 
Published: April 2005

Transmission characteristics of a rectangular waveguide with a perpendicularly inserted mercury-vapor discharge tube, have been measured. The waveguide was excited in the TE01 mode and the plasma column was either perpendicular or parallel to the electric vector of the waveguide mode. In the first case the transmission spectrum contains the well-known Tonks-Dattner resonances and some additional unexplained small peaks. In the second case the transmission spectrum has only small peaks superimposed on a smooth curve. Noise emission spectra were also measured for both polarizations and showed the same characteristics as the absorption spectrum.
To explain these results, dispersion curves were measured for the symmetric, dipole, and quadrupole modes propagating on the plasma cylinder. In addition the dispersion curve for a new symmetric mode was measured. This mode is of the same nature as the fast dipole modes responsible for the subsidiary Tonks-Dattner resonances. By combining these experimental results it has proved possible to gain an understanding of how the various peaks in the transmission spectrum are caused by coupling to plasma waves. In particular, the small previously unexplained peaks are due to coupling to slow plasma waves as also has been proved by direct measurement of the slow waves leaking out through the holes in the waveguide.