bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Expansion of Copper from 20 to 800 K—Standard Reference Material 736
Authors: Hahn Thomas A.
Published: February 2004

Copper is the first of a series of materials that will be certified as thermal-expansion standards by the National Bureau of Standards. The results of tests on five specimens indicate the stock is of consistent quality so that it may be certified as Standard Reference Material 736. A Fizeau interferometer was used for the expansion measurements. Above room temperature a controlled-atmosphere furnace using a calibrated Pt vs Pt-10% Rh thermocouple was used. Below room temperature a cryostat capable of operation with both liquid nitrogen and helium was used with a calibrated platinum resistance thermometer. Values of expansivity were calculated between equilibrium temperatures. The expansivity was used in the analysis of the data. Third-order polynomials were fitted to the data for each of the five specimens in the overlapping temperature ranges from 0 to 70 K, 50 to 270 K, and 210 to 800 K to test for variations between the specimens. The deviations between the five equations were well within the standard deviations of the data for each of the specimens in the respective temperature intervals. All the expansivity data were then pooled and used to obtain an equation for each of the temperature ranges given above. These equations and their integrals were used to calculate the final values of expansivity and expansion, respectively. The results of the statistical analysis of the expansion and expansivity data are presented. A comparison is made with the data in the literature.
Stress and Thermal-Expansion Coefficient of Chemical-Vapor-Deposited Glass Films
Authors: Sunami Hideo , Itoh Yokichi , Sato Kikuji
Published: February 2004

The stress in thin films of chemical-vapor-deposited (CVD) glass on Si substrates was measured by the Newton-ring method. The CVD films studied were Silane-oxidized SiO2, phosphosilicate glass and borosilicate glass deposited at 400°–450°C. Stress reduction due to moisture absorption was observed in the CVD films, but it was not observed in the sputtered SiO2 and the thermally grown SiO2 films. The initial tensile stress in the CVD films changed into compressive stress after heat treatments at 600°–900°C. By measuring the stress at elevated temperatures, the intrinsic stress was reduced from the total stress. From the thermal stress measurement, the thermal-expansion coefficient and the elastic constant of the CVD glass films were estimated.
Thermal Expansion of Extruded Graphite-ZrC Carbide Composites
Authors: Cowder L. R. , Zocher R. W. , Kerrisk J. F. , Lyon L. L.
Published: February 2004

The thermal expansion of extruded graphite-ZrC composites was measured over the temperature range 20°–2500°C and over a composition range 0–0.4 volume fraction of carbide, for directions parallel and transverse to the extrusion axis. The thermal-expansion furnace was a 4-in.-i.d. by 60-in.-long horizontal graphite resistance heater in which a 30-in.-long sample was passively heated. Measured thermal expansion of the composite are compared with those calculated. Calculations using elastic-constant data of the composite material are in good agreement with the measurements.
Thermal Expansion and Phase Equilibria of the Carbon-Saturated Plutonium Carbides
Authors: Green J. L. , Leary J. A.
Published: February 2004

An x-ray diffractometer furnace has been developed for use in the study of the high-temperature properties of refractory compounds of plutonium. The furnace design is based on a resistance heated strip which serves as the sample support. The mechanics of the support system are such that the location of the scattering center of the sample is maintained throughout the temperature range of the instrument, i.e., room temperature to 2500°C. The thermal expansion characteristics of carbon saturated Pu2C3 and PuC2 were determined. A least-squares fit of the lattice dimension data for Pu2C3 in the temperature interval from room temperature to 1600°C yielded Δa/a0=(1.29±0.02×10−5)(T−25)+(2.07±0.14×10−9)(T−25)2,where a is the lattice dimension in Å, and T is the temperature in °C. A least-squares fit of the lattice dimension data for fcc PuC2 in the temperature interval from 1660°C to 2000°C yielded Δa/a0=(17.9±1.6×10−6)(T−1660).
Invar Anomaly
Authors: Colling D. A. , Carr W. J.
Published: February 2004

The origin of the large volume magnetostriction responsible for the Invar anomaly is discussed with respect to several recent theories. Magnetic and thermal expansivity measurements of Fe–Ni–Mn alloys with constant Ni/Fe ratio of 2/3 indicate qualitative agreement with Zener's theory based on competing exchange interactions. Coercive force (Hc) measurements of an Fe–Ni–Co alloy containing mixed martensite and austenite ferromagnetic phases display a maximum Hc at the Curie temperature (θγ) of the austenite which is known to display the Invar anomaly. The sharp change in the value of Hc at θγ is contrary to theories based on concentration fluctuation.
Electronic Structure and Anomalous Thermal Expansion in FeF2 and VO2
Authors: Hazony Y. , Perkins H. K.
Published: February 2004

The negative thermal expansion coefficient (TEC) in FeF2 and the large positive one in VO2, along the c axis, are explained by a model which emphasizes the changes in force constants, resulting from the spatial rearrangement of the electronic charge surrounding the cation, when low-lying electronic states are thermally populated. The TEC data are compared for 14 rutile-type crystals. It is significant that all the compounds studied which involve unequally occupied t2g electronic orbitals display TEC anomalies.
Magnetic Contribution to the Thermal Expansion in an Itinerant Antiferromagnet
Authors: Bartel L. C.
Published: February 2004

In this paper the magnetic contribution to the isotropic lattice contraction in an itinerant antiferromagnet, described by the Hubbard model, is discussed. The isotropic lattice contraction is assumed to arise from the electron-lattice interaction. The spin polarization per site and the isotropic lattice contraction are calculated for a single half-filled band, simple cubic system in a tight-binding approximation with several ratios of bandwidth to intra-atomic exchange parameters, as well as several electron-lattice coupling parameters. The results of the calculations show that for itinerant antiferromagnetic materials, the magnetic electrons produce, near the transition temperature, a lattice contraction which is less in the antiferromagnetic state than in the paramagnetic state. Hence, there would be an apparent expansion in the material at the transition temperature for a decreasing temperature. It is anticipated that the theory given in this paper contains the essential features of a more elaborate treatment.
Neutron and Brillouin Scattering in Quantum Crystals
Authors: Horton G. K. , Goldman V. V. , Klein M. L.
Published: February 2004

Inelastic coherent neutron scattering and stimulated Brillouin scattering of light are discussed in the framework of first-order self-consistent theory of quantum crystals. The theory is applied to solid argon over the temperature range 4°–77°K and over a range of pressures from 0 to 200 atm. We show that anharmonic effects are substantial. Thermal expansion effects are identified and discussed separately. Our work is based on a (6–12) Lennard-Jones potential with parameters fixed to the sublimation energy and lattice constant of Ar at 0°K.
Mode-Grüneisen Parameters and Thermal-Expansion Coefficient of NaCl, CsCl, and Zinc-Blende-Type Crystals
Authors: Vetelino J. F. , Namjoshi K. V. , Mitra S. S.
Published: February 2004

The temperature dependence of the coefficient of thermal expansion of a number of ionic and partially ionic crystals is calculated using a modified rigid ion model and a shell model of lattice dynamics. The model parameters are obtained from long-wavelength optic mode frequencies, elastic constants and the high-and low-frequency dielectric constants. Using the pressure derivatives of these quantities, mode-Grüneisen parameters as functions of wave vectors are next obtained. Thermal expansion coefficient is calculated from the Grüneisen parameters in the quasiharmonic approximation. The calculated values compare well with experimental data.
Deformation-Dipole Calculation of the Coefficient of Thermal Expansion for KBr
Authors: Hardy Robert J. , Karo Arnold M.
Published: February 2004

The deformation-dipole model for alkali halides is extended to include anharmonic effects. The linear coefficient of thermal expansion of KBr is calculated without adjustable parameters. Anharmonicities in the nearest-neighbor overlap forces, in the long-range Coulomb forces, and in the deformability of the ions are included in the model. Good agreement with experiment is obtained.
Thermal Expansion of Solids Regarding Phonons as Defects
Authors: Holder J. , Granato A. V.
Published: February 2004

A general method given earlier for the calculation of thermodynamic properties of solids containing defects is extended to include phonons. This provides a unified treatment in which phonons are treated on the same footing as other defects. In this method, the thermodynamic properties are expressed in terms of pressure and temperature derivatives of the free-energy change per defect. Treating phonons in this way, one recovers the usual thermodynamic relations, where now the temperature is interpreted as a measure of the concentration of defects. In order to investigate further the relationship between thermal and defect properties the general calculation of thermal expansion is carried out for the classical elastic limit. This leads to a distinction between static anharmonic and kinetic contributions to the thermal expansion. The fact that thermal effects and the effects of other types of defects are of the same order of magnitude is more evident by this comparison.
Piezoresistivity Coefficients in Manganin
Authors: Barsis E. , Williams E. , Skoog C.
Published: February 2004

The piezoresistivity coefficients for Manganin have been determined from the static and shock pressure dependence of the resistance. An analysis is presented which relates the piezoresistivity coefficients to resistance changes under conditions of one-, two-, and three-dimensional dynamic strains and hydrostatic strain. This analysis shows that the piezoresistance values depend on the mode of strain and reconciles the different piezoresistance values, reported in the literature, to a unique but pressure dependent piezoresistivity coefficient. The dynamic piezoresistance predicted from static piezoresistance pressure data and mechanical data using this analysis is in good agreement with the observed values. The observed piezoresistivity which is of opposite sign to that predicted from the pressure dependence of the lattice scattering, is discussed in terms of an s-d scattering model for Manganin and other alloys of copper containing elements with unfilled 3d electron states. This model suggests that several of these alloys have a higher coefficient than Manganin, and may explain the large positive piezoresistance reported in the literature for calcium, strontium, and barium.
Elastic Fields and Energies of a Circular Edge Disclination and a Straight Screw Disclination
Authors: Huang Wen , Mura T.
Published: February 2004

The displacement and stress fields for a circular edge disclination are derived from Green's tensor function. The elastic strain energy of this circular edge disclination is calculated and compared with the energy of two different kinds of circular dislocation loops. Finally, the stress field and elastic strain energy of a straight screw disclination is computed and is compared to the case of a straight screw dislocation.
Optically Induced Refractive Index Changes in BaTiO3
Authors: Townsend R. L. , LaMacchia J. T.
Published: February 2004

The phenomenon of ``optical damage,'' that is, optically induced changes in the index of refraction, can be used as a form of holographic storage in transparent ferroelectric crystals. In this paper we describe a series of experiments which characterize the optical damage in ferroelectric BaTiO3. This is done by recording in a single crystal of the material a plane wave hologram, i.e., a diffraction grating, with a laser at one wavelength and reconstructing the hologram with a laser at another wavelength. The time-dependence and steady-state value of the diffracted light is studied with respect to variations in incident light intensity, temperature, writing wavelength, and grating spacing. A model describing the optical damage, based on the work of Chen [F. S. Chen, J. Appl. Phys. 40, 3389 (1969)] and Johnston [W. D. Johnston, Jr., J. Appl. Phys. 41, 3279 (1970)] is presented and the results explained in terms of this model.
Diffusion in α-Fe–Si Alloys
Authors: Borg R. J. , Lai D. Y. F.
Published: February 2004

The diffusion coefficients for both Fe and Si diffusing in dilute α-Fe–Si alloys have been measured. A value for the vacancy-silicon binding energy has been calculated and an explanation offered for the concentration dependence of the silicon-diffusion coefficients.
Transversely Spark-Initiated Chemical Laser with High Pulse Energies
Authors: Jacobson T. V. , Kimbell G. H.
Published: February 2004

Peak powers exceeding 1 kW of 5.0-μ radiation have been obtained from a pulsed chemical laser. Reactions of CS2/O2/inert gas mixtures were initiated by means of a transverse spark discharge. A maximum pulse energy of 26 mJ was obtained. The pumping reaction was believed to be O+CS=CO+S. Laser action was observed on 79 P-branch transitions in the 13→12 to 2→1 transitions of ground state CO.
Near-Bandgap, Narrow-Spectrum, Low-Loss, Volume-Excited GaAs Laser (77°K) with Time-Uniform Output
Authors: Dapkus P. D. , Holonyak N. , Keune D. L. , Burnham R. D.
Published: February 2004

Data are presented showing that it is possible to operate lightly doped GaAs as a laser at energies exceeding 1.500 eV at 77°K (Eg=1.513 eV), to obtain essentially monoenergetic operation well above threshold and to avoid the mode jumping effects common to optically pumped lasers. This has been accomplished by volume exciting the center n region (selective absorption) of a low-loss n+/n/n+ epitaxial wafer under conditions of limited absorption which in turn allows stabilization of the carrier concentration and the photon energy of the recombination radiation.
Effect of Pressure and Strain Rate on the Shear Strength of Beryllium
Authors: Abey A. E.
Published: February 2004

The shear strength of beryllium was measured at strain rates of 3.5×10−5, 3.6×10−3, and 3.7×10−1 sec−1. Measurements were taken under nearly hydrostatic pressures of 21, 44, and 63×108 N/m2. The shear strength was found to increase with both pressure and strain rate. A sample dislocation model was used to find an activation energy of 0.19 eV for dislocation motion. The model also gives an activation volume of 2.4×10−30 m3 per unit length of moving dislocation. Data taken at a strain rate of 3.7×10−1 sec−1 to strains of approximately 40 indicate no ductile strain below a pressure of 6×108 N/m2 and an increase in ductile strain of 1.2 for each increase in pressure of 109 N/m2 above this value.
1/v Dielectric Track Detectors for Slow Neutrons
Authors: Schultz W. W.
Published: February 2004

The fabrication of track detectors with boron atoms uniformly dispersed throughout the volume of the track detector material has been successfully accomplished. Because of their small size they have little effect on the neutron flux one is trying to measure. It is possible to make measurements of neutron flux densities over a range of six to seven decades. Track density is found to be a function of the thickness of detector surface etched away and the ranges of the alpha particle and lithium recoil particle resulting from the capture of a neutron by a 10B atom. At etching proceeds, track density may increase or decrease depending on the etching rate of the bulk material relative to the maximum etching rate perpendicular to the particle path. A new method of studying diffusion through thin layers at the surface of a solid is suggested.
Threshold Calculations for an Optical Parametric Oscillator Employing a Hemispherical Resonator
Authors: Ammann E. O. , Montgomery P. C.
Published: February 2004

A calculation of optical parametric oscillator threshold has been carried out for an oscillator which employs a hemispherical resonator. The analysis considers the effects of focusing and double refraction, and makes possible the calculation of threshold as a function of the focusing parameter ξ and double-refraction parameter B. The analysis is similar to that carried out by Boyd and Kleinman for a different class of optical resonators. Their analysis assumes that the pump beam is centered (longitudinally) with respect to the focus of the oscillator pump beam. In a hemispherical resonator, however, only half of the pump-beam focal region can be utilized because of the resonator configuration. As one would expect, oscillator threshold is higher for the hemispherical case than for the Boyd and Kleinman case. However, the increase is at most a factor of 2 (when beam walkoff is absent, i.e., when B=0), and gradually goes to unity as B increases in size. Thus by using a hemispherical resonator in an optical parametric oscillator, one gains experimental convenience at the expense of a slight increase in oscillator threshold.
Dependence of Linear Electro-Optic Effect and Dielectric Constant on Melt Composition in Lithium Niobate
Authors: Turner E. H. , Nash F. R. , Bridenbaugh P. M.
Published: February 2004

It has recently been reported by Hirano [Jap. J. Appl. Phys. 8,399 (1969) and J. Phys. Soc. Japan Suppl. 28, 90 (1970)] that the dc half-wave voltage in lithium niobate increases appreciably with any departure from a melt stoichiometry (Li/Nb)m=1.00. Our measurements of the low- and high-frequency half-wave voltages indicate no variation over the range of melt stoichiometries originally considered. We have also measured the effect of compositional variations upon the low- and high-frequency dielectric constants and we find a smaller change and in the opposite sense from that reported by Hirano. We discuss the indirect evidence which argues against any special importance being attached to the particular composition (Li/Nb)m=1.00. Theoretical estimates of the anticipated changes in the half-wave voltages with composition support our experimental conclusions.
Energy Levels in Cobalt Compensated Silicon
Authors: Moore J. S. , Chang M. C. P. , Penchina Claude M.
Published: February 2004

Measurements of the temperature dependence of resistivity and Hall coefficient in cobalt-doped silicon show a donor level 0.40 eV from the valence band and an acceptor level 0.53 eV from the conduction band. These levels appear to be due to different charge states of the same center. Absorption and photoconductivity measurements support these determinations. Closed tube diffusions of silicon wafers on which cobalt has been evaporated result in maximum concentrations of electrically active cobalt of about 3×1014 cm−3.
Dislocation and Surface Scattering in Polycrystalline Germanium Films
Authors: Ramey R. L. , Jesser W. A. , Bowers T. L.
Published: February 2004

A computer-aided analysis of the transport mechanism for holes in polycrystalline germanium films indicates that the density of dislocation lines obeys the relation N=NC[1+βD exp(−a/δD)],where NC, βD, and δD are constants determined by experimental growth conditions. The film thickness is a. The energy bands are bent down at each surface with uB≃−10 and uS≃−7 in accordance with the surface scattering theory developed by Schrieffer and Greene, Frankl, and Zemel.
Interference Effects in the Reflection of Low-Energy Electrons from Thin Films of Au on Ir
Authors: Thomas R. E.
Published: February 2004

Retarding field measurements were taken on thin films (10–−-100 Å) of Au evaporated on an Ir (111) surface. In the range of 0–5 eV the current-vs-voltage plots exhibited a decaying periodic variation in amplitude. The amplitude and period of the variations both decreased with film thickness. This interference phenomenon is interpreted as being due to electron reflection occurring at both the film-vacuum and the film-substrate interfaces. Measurements of the period as a function of film thickness agree well with a simple free-electron picture for the phase shift experienced by electrons traversing the film, giving an effective inner potential of 16 eV for Au. From the temperature dependence of the energy at which maxima and minima occur the thermal expansion coefficient for the films is determined. Also, estimates of the mean-free path for electrons in the film are obtained from the decay of the variation amplitude with thickness. Values obtained for both these quantities are consistent with previously published values.
Quantum-Mechanical Random-Number Generator
Authors: Schmidt Helmut
Published: February 2004

For generating the numbers 1, 2, … M in random sequence, an electronic modulo-M counter is used, driven by the pulses from a high-frequency pulse generator. If the pulse train is interrupted at a random time, then the counter stops at random in one of its M possible states, producing thus a random-number modulo M. The random time is the time at which a Geiger-Mueller tube registers an electron from a 90Sr source. The electronic circuitry is designed such that variations in the characteristics of the components do not impair the randomness. Due to the simplicity of the circuit, the degree of randomness obtainable can be discussed in detail. The randomness of the primarily generated ``basic sequence'' is limited by the finite value of the quotient (pulse-generator frequency) / (number-generation frequency). An extremely high degree of randomness can be realized by ``contracting'' the basic sequence, i.e., by adding (modulo M) strings of k (k=2, 3, 4, or even higher) successive numbers of the basic sequence, to form one number of the final sequence. This contraction can be achieved very easily by interrupting the pulse train only after exactly k electrons have been recorded by the Geiger-Mueller tube. The performance of a generator was tested by recording a basic sequence of generated numbers on paper tape. For probing the long-time reliability of the generator these recordings were made over an 18 months period, and the randomness tests were designed to discover also temporary malfunctions. In accord with the theoretical expectation, these tests did not indicate any deviation from randomness.
Initial Processes in CO2 Glow Discharges
Authors: Buser R. G. , Sullivan J. J.
Published: February 2004

Initial dissociation rates of CO2 in pure CO2 glow discharges and CO2 mixtures with He, N2, H2 have been determined in the 1-Torr pressure range using a mass spectrometric sampling technique combined with plasma diagnostic methods. The observed results for the pure CO2 case are discussed in terms of dissociative attachment and collisional dissociation of vibrationally excited CO2 molecules both of which contribute to the dissociation process; most influential in mixtures is H2 which reduces the dissociative process. At the same time, the quasistationary values of the CO2–CO–O2 mixture as well as that of CO2–CO–O2 with He, N2, H2 have been measured: [CO2]/[CO][O2]1/2 is approximately constant at pressures >500 mTorr and linearly dependent upon H2 concentration.
Double Injection in the Perfect Insulator: Further Analytic Results
Authors: Rosenberg Lawrence M. , Lampert Murray A.
Published: February 2004

The general problem of double injection into a perfect insulator, free of traps and of thermal free carriers, does not yield to a complete, analytical description. A complete solution is presented for the limiting cases of very large and very small σR, where σR is the electron-hole recombination cross section. The first situation corresponds to a pair of back-to-back, one-carrier, space-charge-limited currents, the second to an injected plasma. The I-V characteristics obtained in these two limits agree precisely with the earlier general analytical result of Parmenter and Ruppel. For intermediate values of σR the Regional Approximation method is used to obtain an approximate solution. The field and density distributions, obtained for large, intermediate, and small values of σR, are the first available for this problem. The constant-lifetime and bimolecular-recombination injected plasmas are compared and found to have remarkably similar distributions.
Photoionization Measurements in Air, Oxygen, and Nitrogen
Authors: Penney G. W. , Hummert G. T.
Published: February 2004

Ion-chamber measurements of the photoionization produced by point-to-plane corona discharges in air, oxygen, and nitrogen (commerical grade) over a pressure range of 0.1 to 18 Torr are reported in this paper. The results are expressed in a generalized form that reduces the data for each gas to a single curve relating photoionization to pressure (p) times distance (R) from the discharge. The range of Rp values is between 1 and 550 cm Torr. Absorption coefficients are compared to those reported by other investigators by plotting absorption coefficient/pressure vs Rp. In air and oxygen the values fall along a common curve. These results indicate that relating the ion-chamber currents to Rp in the manner described in this paper may provide a useful basis for calculating the photoionization produced by discharges in these gases.
Measurement of the Energy Dissipated in the Electrostatic Spraying Process
Authors: Huberman M. N.
Published: February 2004

Retarding potential and cylindrical electrostatic analyzer experiments have determined the equivalent voltage loss needed to electrostatically spray positively charged droplets of glycerol doped with sodium iodide. The cylindrical analyzer was also used as a mass spectrometer to identify in-flight evaporation processes. Evaporation from discrete multimolecular droplets containing one sodium ion in conjunction with low numbers of glycerol molecules was identified. The kinetics of this process made it possible to assign an energy loss of 400±200 V for the spraying process.
Pulse Lengthening Via Overcoupled Internal Second-Harmonic Generation
Authors: Murray James E. , Harris S. E.
Published: February 2004

The paper discusses the use of internal second-harmonic generation as a means of lengthening the pulses of Q-switched lasers. The second-harmonic generator acts as both a nonlinear power-dependent loss and as an output coupler for the laser. The lengthening arises if the coupling to the second harmonic is greater than that necessary to maximize the peak second-harmonic power. It is shown that a pulse-lengthening factor of about 100 should be obtainable.
Temperature Dependence of the Anisotropy in Evaporated Polycrystalline Ni–Fe Films
Authors: Flanders P. J. , Doyle W. D.
Published: February 2004

The temperature dependence of the induced anisotropy constant K and saturation magnetization Ms in evaporated polycrystalline Ni–Fe films was determined relative to room-temperature values over a broad alloy range from 100° to 293°K. Within experimental error, K(T)/K (293°K) = [Ms(T)/Ms(293°K)]q, where q=3.6±0.2 for all compositions. This result suggests that the anisotropy in evaporated films is a single-ion effect. Further, if the anisotropy can be described by a combination of pair ordering and constraint release, both mechanisms are single-ion effects.
Effects of Pressure on the Magnetization of Ferrites: Anomalies Due to Strain-Induced Anisotropy in Porous Samples
Authors: Wayne R. C. , Samara G. A. , Lefever R. A.
Published: February 2004

Anomalously large changes in the magnetization as a function of hydrostatically applied pressure have been observed over a range of sample densities and applied fields in porous polycrystalline (ceramic) ferrites such as NiFe2O4 and YIG. These changes can be explained on the basis of anisotropy energy resulting from nonisotropic strain. The experimental results show that large nonisotropic strains can obtain in porous samples and thus, care must be exercised in interpreting ``hydrostatic'' measurements on porous materials especially when the property being measured is known to be strongly dependent on the nature of the induced strain. For single-crystal YIG, the saturation magnetization per unit mass is found to be independent of pressure as is expected since its magnetic moment is the spin-only value.
Pressure and Temperature Dependence of the Elastic Constants of RbCl, RbBr, and RbI
Authors: Ghafelehbashi M. , Dandekar D. P. , Ruoff A. L.
Published: February 2004

This paper presents the ultrasonic measurements of the elastic constants of RbCl, RbBr, and RbI as a function of pressure up to approximately 4 kbars in the temperature range of 120° to 300°K. The reduction of the raw data is analyzed according to the self-consistent method suggested by Cook and is discussed at length so as to clarify the limitations as well as the precision of the final results presented in this paper. The results of adiabatic as well as the isothermal values of the elastic-constant measurements at pressure are given together. Pressure derivatives of the elastic constants of the above salts under different thermodynamic conditions are calculated and are given separately. Finally the Cauchy relation and anisotropy are discussed.
Iterative Procedure to Estimate the Values of Elastic Constants of a Cubic Solid at High Pressures from the Sound Wave Velocity Measurements
Authors: Dandekar Dattatraya P.
Published: February 2004

In order to estimate accurately the values of the elastic constants of a solid at high pressure and at an arbitrary temperature T from the ultrasonic measurements of the velocities of elastic waves propagated in solids as a function of pressure at the temperature T, it is necessary to know a priori the compressibility of the solid as a function of pressure at the temperature T. However, this latter information is not always available. Hence, one has to make some kind of approximation to estimate the values of the elastic constants of solids at high pressure. The procedure developed here is more consistent than previous procedures. It requires a priori knowledge of the following values: the thermal expansion coefficient, its temperature derivative, the specific heat at constant pressure of a solid at one atmosphere, and the travel-time measurements of the elastic waves propagated through the solid as a function of pressure at a temperature T or at more than one temperature.
Microdeformation of Solids
Authors: Macmillan N. H. , Gane N.
Published: February 2004

Small-scale indentation experiments performed on nonmetallic specimens are reported. These experiments are very similar to others performed by one of us (N.G.) on metal specimens and reported in a previous issue of this journal. Again, it is believed that the theoretical strength of the perfect lattice is being observed.
Dislocation Damping at High Strain Rates in Aluminum and Aluminum-Copper Alloy
Authors: Victoria M. P. , Dharan C. K. H. , Hauser F. E. , Dorn J. E.
Published: February 2004

Impact shear tests have been used to study the dependence of shear stress with shear-strain rate at strain rates ranging from 0.5×104 to 2.2×104 sec−1 in pure Al, prestrained Al, and Al-2 at. % Cu alloy. Within this strain-rate range a linear relationship was found between shear-stress and shear-strain rates, indicating the presence of a viscous drag on dislocations. The dependence on temperature of this viscous damping was investigated between 10° and 293°K. The results are discussed in terms of theories of phonon viscosity and phonon scattering, and of electron viscosity at low temperatures.
Marvel-Nuclear Driven Shock-Tube Experiment
Authors: Glenn H. D. , Crowley B. K.
Published: February 2004

A 2.2-kton nuclear explosive was detonated underground at one end of a 122-m long, 1-m i.d. horizontal tunnel at the Nevada Test Site. The purpose of the experiment was to study the hydrodynamic flow of energy down a tunnel from a nuclear explosive. This report describes the experimentation utilized to record luminosity of the shock front for the first 15 μsec and time of arrival of the shock front at specific positions along the tunnel. The observed temperature, determined from shock-luminosity data and the blackbody radiation assumption, dropped from 11.8 to 2.3 eV at times of 3.2 and 18 μsec respectively after the peak energy output of the nuclear explosion. The shock wave traversed the 122 m in approximately 4 msec, with a velocity ranging from about 13 cm/μsec near the shot point to approximately 1 cm/μsec at the far end.
Image Upconversion: Part III
Authors: Firester A. H.
Published: February 2004

We discuss in detail the imaging properties of nonlinear image upconverters. Three-dimensional image conversion is shown to be possible. The dependence on the system parameters of the converted image's resolution, location, and chromatic aberration is treated. Image conversion with object and pump beams of the same frequency is experimentally demonstrated and the experimental techniques discussed.
Ion-Burst Excited by a Grid in a Plasma
Authors: Ikezi H. , Taylor R. J.
Published: February 2004

The ion-burst excited by a pulsed mesh grid in a plasma is studied experimentally in connection with the sheath structure. The energy distribution of the ions participating in the burst is found to be a broad one. The attenuation of the peak amplitude of the response is confirmed to be due to collisionless damping. The shape of the ion-burst is accounted for by the application of the Child-Langmuir law which gives the approximate potential profile of the sheath around the grid. The potential is also measured by using ion transit time effects in the sheath.
Defects Observed in Electron Irradiated Pure Silver by Electron Microscopy
Authors: Shimomura Y.
Published: February 2004

Nominally 99.9999% pure silver strips were irradiated near 140°K with 3 MeV electrons. Fluences ranged from 0.05 to 6.7×1018 electrons/cm2. In order to observe defects which exist in irradiated specimens by electron microscopy at temperatures below stage III annealing, specimens were thinned, washed, and mounted on a specimen holder below −60°C. They were also dried below −60°C and observed using a liquid-nitrogen cooling stage. A large number of interstitial loops were observed below stage III. The number of loops was constant but the size of the loops increased with increasing fluence. They shrank and disappeared during stage III annealing. After annealing at 0°C, another kind of small dot defects were observed. The results suggest that the stage III annealing occurs by a vacancy or divacancy migration in electron irradiated pure silver.
Theory of Transverse Extension of Gunn Domains
Authors: Shoji Masakazu
Published: February 2004

A theory describing the growth of Gunn domains transverse to their direction of travel is developed. This theory is based on a model in which the dipole moment of a domain causes the field immediately adjacent to its lateral edge to exceed the negative resistance threshold. As the dipole moment begins to build up there, it causes the field farther along the lateral dimension to exceed threshold. From this model the velocity of transverse domain growth can be calculated as a function of the bias field and the maximum domain field. The calculated values of about 108 cm·sec−1 are in reasonable agreement with available experimental data.
Spectrophotometric Thickness Measurement for Very Thin SiO2 Films on Si
Authors: Rand Myron J.
Published: February 2004

Measurement of the intensity of light reflected from SiO2-coated Si, compared with that reflected from the bare Si substrate, may be used for a SiO2 thickness measurement in the range below 1000 Å where conventional methods are difficult to apply. By going into the ultraviolet much improved sensitivity is obtained, and at 200 nm an 18 Å film of SiO2 can be detected. Relative reflectance curves for 589, 400, 300, and 200 nm derived from optical theory are presented; thicknesses measured using these curves are in good agreement with those from ellipsometry. The only apparatus required is a commercially available uv-vis spectrophotometer equipped with a microbeam reflectance attachment operating at near-normal incidence. Thickness measurement requires a spot 1–2 mm in diameter and is simple, rapid, and nondestructive.
Auger Electron Spectroscopy of Clean Gallium Arsenide
Authors: Uebbing John J. , Taylor Norman J.
Published: February 2004

The electron-excited Auger spectrum of vacuum-cleaved GaAs is presented. Measurements were made for initial holes in the L, M, and N shells. The different peaks are identified by their energy and by using trend lines for similar peaks from the elements Z=22 to Z=33.
Magnetic and Crystallographic Properties of Ferritin
Authors: Girardet J. L. , Blaise A. , Chappert J. , Lawrence J. J. , Feron J. , Picoche J. C.
Published: February 2004

The function of ferritin is to stock the iron present in the body. Ferritin consists of a protein shell surrounding a core which is mainly an iron hydroxide FeOOH. Mössbauer effect and magnetic measurements in the temperature range 2°–300°K show ferritin to be superantiferromagnetic with grains 70 Å in diameter. This condition is characterized by a blocking temperature and a thermoremanent magnetization. The magnetic moment of each grain is about 1.2 × 10−18 emu and the surface anisotropy is 5.8 × 10−2 erg/cm2. In aqueous solution, ferritin retains its magnetic properties apart from a slight modification due to the penetration of water which expands the grains. Ferritin can contain up to a maximum of 23 wt% iron without any profound effect on the basic magnetic properties. High pulse field experiments (175 kOe) show ferritin to behave as a metamagnet with a threshold field of 75 kOe. The core of the molecule has hexagonal crystal structure with a = 11.79 Å and c = 9.90 Å, resembling the planar compact structure of oxygen in δ-FeOOH. The iron atoms are situated on the tetrahedral and octahedral sites of the lattice. Some of this work has been published elsewhere: A. Blaise, J. Chappert, and J. L. Girardet, Compt. Rend. 261, 2310 (1965); A. Blaise, J. Feron, J. L. Girardet, and J. J. Lawrence, Compt. Rend. 265, 1077 (1967); J. L. Girardet and J. J. Lawrence, Bull. Soc. Franc. Mineral. Crist. 91, 440 (1968).
Magnetic Studies of the Alloy System SnTe–MnTe
Authors: Mathur M. P. , Deis D. W. , Jones C. K. , Patterson A. , Carr W. J. , Miller R. C.
Published: February 2004

Magnetic ordering and superconductivity have been investigated in the system Sn0.97-xMnxTe for 0.00001≤x≤0.16 over the temperature range 0.02≤T≤300°K. Reciprocal Hall coefficient, 1/Re, for all these samples was ∼1021 cm−3. Samples with x>0.005 showed ferromagnetic ordering with the Curie temperatures varying linearly with x. For 0.0001<x<0.005, neither magnetic ordering nor superconductivity were observed above 0.02°K. In samples with x<0.0001 superconductivity has been observed with the transition temperatures being depressed below that for Sn0.97Te (Tc≃0.20°K). Measurements have also been made on samples with constant manganese concentration and varying carrier density. Heat capacity measurements between 2°–30°K showed anomalies attributable to the magnetic coupling of the Mn ions. These results will be discussed in terms of current long-range indirect-exchange interaction theories.
Ferromagnetic and Spin Wave Resonance at High Pressure
Authors: Uhrig T. A.
Published: February 2004

The pressure dependence of the magnetization (+0.105%/kbar), g value (+0.094%/kbar), and exchange stiffness D(+0.054%/kbar) have been measured by ferromagnetic and spin wave resonance experiments in ambient pressures from one bar to five kbars at room temperature in 80–20 Permalloy. Since the film is evaporated on a sapphire substrate, the film is not deformed hydrostatically but is strained by −0.0293%/kbar in thickness and by −0.0106%/kbar in the transverse directions. The strain dependence of the exchange stiffness was analyzed to obtain the atomic distance dependence of the interatomic exchange [d(lnJ)/d(lna = −5.2] using the Heisenberg model and the pressure dependence of the band splitting parameter Δ(+0.048%/kbar) using the itinerant electron model.
Evidence for an Exchange Coupling at the Interface between Two Ferromagnetic Films
Authors: Hoffmann F. , Stankoff A. , Pascard H.
Published: February 2004

In a first part, we estimate the effect of dynamic pinning [C. F. Kooi, E. P. Wigen, M. R. Shanabarger, and J. V. Kerrigan, J. Appl. Phys. 35, 791 (1964)] due to two ferromagnetic layers upon the spin-waves resonances in a sandwiched film having a higher magnetization, assuming the interface interaction energy to be of an exchange type. Experiments performed on epitaxial films of Permalloy, symmetrically coupled with two nickel layers of various thicknesses, exhibit results in excellent agreement with theory and provide a reproducible value of the interface energy which is one-tenth of that of the bulk exchange energy.
Magnetostriction of Co and Co-8% Fe Crystals
Authors: Headley L. C. , Pavlovic A. S.
Published: February 2004

The magnetostriction of single crystals of hcp Co and fcc Co-8% Fe alloy has been measured as a function of temperature, magnetic field, and magnetization direction. The saturation magnetostriction constants for hcp Co, and fcc Co-8% Fe are presented. They are compared with previous results and their relation with present theoretical ideas discussed. Forced magnetostriction data are also discussed.
Iron-Silicon-Aluminum Nonoriented Electrical Sheets
Authors: Regitz L. J.
Published: February 2004

Nonoriented electrical sheets with good ductility and superior magnetic properties can be produced from steel containing Si and Al by processes involving cold reduction and high-speed continuous annealing. A preferred composition, containing between 2% and 3% Si and between 2% and 3% Al has core losses similar to, and permeabilities vastly superior to, those generally associated with AISI M-14 grade sheets. Unlike Si-steel sheets having similar resistivity and total alloy content, these Fe–Si–Al sheets are ductile and can be readily wound and punched. Further advantages of this steel sheet include improved surface finish and flatness, lower specific gravity, a low degree of preferred orientation, and a highly insulating, adherent surface oxide that is developed during the process anneal by action of the annealing atmosphere on the alloying elements in the sheet.
Observation of Dynamic Domain Size Variation in a Silicon-Iron Alloy
Authors: Haller T. R. , Kramer J. J.
Published: February 2004

It was recently noted that the dynamic domain structure in a ferromagnetic material may differ markedly from that observed under static conditions. In this investigation the dynamic size of magnetic domains in a rectangular single-crystal specimen of an iron-3% silicon alloy (2.5 cm×3.3 cm×0.22 mm with a (001) [100] orientation) was measured using the Kerr magneto-optic effect together with high-speed cinematography. Under dynamic conditions of a 100 Hz sinusoidal induction of saturation amplitude, the average domain width was reduced from the average static width of 2½ times the sheet thickness to about ½ this value. The finer dynamic domain structure could be ``frozen in'' by turning off the applied field during the middle of the magnetization cycle, but the original coarser structure always returned following an ac demagnetization. Measurements in the frequency range 20–100 Hz showed that above a threshold frequency domain width decreased with frequency as (f)−1/2. With a varying amplitude of induction the domain width decreased as (Bmax)−1, above a threshold induction.
Influence of Plastic Deformation on Coercive Field and Initial Susceptibility of Fe-3.25% Si Alloys
Authors: Qureshi A. H. , Chaudhary L. N.
Published: February 2004

Measurements were made of the deformation dependence at room temperature of the coercive field Hc and the initial susceptibility χi and the recovery process was investigated during isothermal annealing. At the same time the dislocation density in the specimens was microscopically determined by metallographic techniques. The results show that the coercive field varies corresponding to the N1/2 proportionality law stated in literature. The initial susceptibility of the material varies approximately as χi=const/N1/2. The relative rate of change in Hc and χi with annealing time for specimens of various degrees of plastic deformation remains constant indicating that a single mechanism of rearrangement and recovery of dislocations determines these magnetic properties. Measurements of mechanical hardness showed that it varies in the same fashion as N1/2. Though indirect experimental evidence of a relation between Hc, χi, and N exists, to our knowledge our investigations are unique as we have made an attempt, with the help of metallographic examination, to relate Hc, χi, and hardness directly with the dislocation density.
NMR Studies of Pd–Rh and Ni–Rh Alloys
Authors: Narath A. , Weaver H. T.
Published: February 2004

Low-temperature (T ≈1°–4°K) measurements of the Knight shift (K), spin-lattice relaxation time (T1), and inhomogeneous linewidth (Δ) of 103Rh in the two alloy systems Pd1−x–Rhx (0.03 ≤ x ≤ 1.00) and Ni1−x–Rhx (0.38 ≤x ≤1.00) have been carried out using transient NMR techniques. In Pd1−x–Rhx both T1T and K vary monotonically with decreasing x, K decreasing from +0.43% to −14.4% and T1T from 9.2 to 0.8 sec°K. The minimum K value agrees with the infinite dilution value K = −14.7% obtained by Rao, Matthias, and Shirley using PAC techniques, and indicates that K is essentially independent of x for Rh concentrations up to ∼5 at.%. The threefold increase in K for 103Rh as a dilute impurity in Pd over that of 105Pd in the elemental metal indicates that the local susceptibility at the Rh sites exceeds that of the Pd sites. Similar results are found in Ni1−x–Rhx with K decreasing from +0.43% to −8.1% and T1T from 9.2 to 1.2 sec°K. However, the susceptibility at the Rh sites appears to be smaller than at the Ni sites in this case. Both alloy systems display severe inhomogeneous broadening of the NMR with Δ ≈ K in some cases. This result demonstrates an extreme sensitivity of the local susceptibility to the near-neighbor environment.
Evidence for Local Effects on the Nuclear Spin-Lattice Relaxation Rate in Ferromagnetic Palladium Iron Alloys
Authors: Chinh P. V. , Skalski S. , Budnick J. I.
Published: February 2004

For some time there has been considerable theoretical work on the role of local exchange enhancement in highly polarizable systems. To date, there has been little experimental evidence for the importance of these local effects in ferromagnetically polarized alloys. We have measured the nuclear spin-lattice relaxation rate in ferromagnetic PdFe alloys in the helium temperature range. Our results for the Pd nuclei indicate that the relaxation rate is a strong function of the nearest neighbor environment. Specifically there is a contribution to the relaxation rate which is proportional to the number of iron nearest neighbors, N, for N=0, 1, 2 over the concentration range from 1 to 7.5 at.% Fe. Furthermore, the relaxation rates at both the Pd sites and the Fe site vary with concentration as the square of the measured high-field susceptibility. This behavior is consistent with either a strong inter-atomic exchange interaction between a Pd and its nearest neighbors, or a variation in the intra-atomic exchange interaction at a Pd site induced by the change in its nearest-neighbor configuration.