bluuebunny/crossref_metadata_2025 huggingface dataset:
A Submicron Sectioning Technique for Analyzing Diffusion Specimens of Tantalum and Niobium
Authors: Pawel R. E. , Lundy T. S.
Published: April 2005

A microsectioning technique for tantalum and niobium was successfully used to remove uniform sections of metal less than 100 Å in thickness from the surface. The technique, based on the formation and subsequent stripping of an anodic oxide film, is presently used to study diffusion phenomena in these metals. The apparent sensitivity is sufficient for low-temperature diffusivity measurements in reasonable times. It may also be possible to describe more quantitatively previously reported ``anomalous'' diffusion behavior near the metal surface. The present paper considers the details of the experimental technique and presents some typical diffusivity data for the diffusion of Nb95 in tantalum.
Magnetic Susceptibilities of Several Salts at Liquid-He3 Temperatures
Authors: Friedberg S. A. , Schriempf J. T.
Published: April 2005

The magnetic susceptibilities of several compounds have been measured between 0.35° and 4.2°K in a He3 cryostat by an audiofrequency mutual-inductance technique. The powder susceptibility of [Cr3(CH3COO)6(OH)2]Cl·8H2O obeys a Curie—Weiss law. Powder data show Co(CH3COO)2·4H2O and Ni(CH3COO)2·4H2O to be paramagnetic down to 0.35°K; the cobaltous salt does not exhibit the anomaly at 0.6°K inferred earlier from adiabatic demagnetization data. The powder susceptibility of Mn(HCOO)2·2H2O departs from Curie—Weiss behavior at these temperatures due to exchange interaction among many of the Mn+ +'s. Powder and single-crystal data on FeCl2·4H2O indicate antiferromagnetic behavior with a Néel point TN∼1°K and preferred spin alignment along or near the monoclinic b axis. The susceptibilities above TN have been analyzed in terms of the energy levels of a single Fe++ ion and the large anisotropy given a reasonable interpretation.
Microwave Properties of Fine-Grain Nickel Ferrite
Authors: Green J. J. , Waugh J. S. , Healy B. J.
Published: April 2005

Microwave measurements have been made on fine-grain nickel ferrite prepared by a flame spray-hot pressing technique. The fine-grain samples have linewidths, below resonance magnetic losses, dielectric loss tangents, and subsidiary absorption thresholds which are considerably larger than those found in samples prepared by conventional techniques.
Improvement of the Ferromagnetic Resonance Linewidth of Single-Crystal ZnY (Ba2Zn2Fe12O22) by a New Growth Technique
Authors: Tauber A. , Dixon Samuel , Savage R. O.
Published: April 2005

By using a new growth technique, ferromagnetic resonance linewidths as low as 8.0 Oe can be obtained in ZnY single crystals at room temperature and 9.0 kMc/sec. These crystals were grown in platinum crucibles from BaO–B2O3 melts. The melts were found to be less volatile and less viscous than NaFeO2 melts. Annealing reduced the linewidth. The best conditions consisted of annealing raw crystals at 750°C in 1 atm of oxygen for 24 h. This treatment reduced the ferrous ion concentration to below the limit of detection, 0.01%, and is considered the major factor in linewidth reduction. These samples were then ground into spheres and polished with successively finer grit abrasives. An exponential decrease in the linewidth was observed as a function of grit size. Linewidth measurements were made using the standard cavity perturbation technique. The diameters of the samples ranged from 0.018 to 0.030 in. (450 to 750 μ). The orientation of spheres in the cavity was such that the microwave magnetic field and the applied field were perpendicular to each other and in the plane of easy magnetization of the material.
Parametric Excitation of Acoustic Wave Instabilities in Ferromagnets
Authors: Tokheim R. E. , Winslow D. K. , Auld B. A.
Published: April 2005

Experimental measurements of saturation effects in single-crystal Zn2Y, with the easy plane lying in the plane of the disk, have been observed experimentally at 1.3 G/sec—below the bottom of the spin-wave manifold. Thresholds observed are comparable with theoretical predictions based upon the assumption of the magnetoelastic pumping effect as the dominant mechanism. In these experiments the order of the first resonant spin-wave instability permitted has been varied from the second to the fifth by adjusting the position of the spin-wave manifold relative to the pump frequency.
Magnetoacoustic Resonance in Lithium Ferrite
Authors: Comstock R. L. , Remeika J. P.
Published: April 2005

The parametric coupling of magnetostatic and elastic modes (magnetoacoustic resonance) has been observed in a single-crystal lithium ferrite sphere. Observation of this effect was made possible by the development of highly ordered stoichiometric lithium ferrite which has the narrowest ferromagnetic resonance linewidth of the spinel ferrimagnets [ΔH(300°K)=1.7 Oe, ΔH(134°K)=0.9 Oe at 5.4 G/sec]. The Q of the oblate-prolate elastic mode for this sphere was found to be 175 000 at 300°K.

An estimate of one of the two magnetoelastic coupling constants resulted in a value B1=65×106 erg cm−3. This estimate was made by comparing the magnetoacoustic threshold for a sphere of this material with the threshold for a sphere of yttrium iron garnet (YIG), for which the coupling constants are known.

A figure of merit for magnetoelastic materials is presented on the basis of which it appears that lithium ferrite may be superior to YIG in some transducer applications.
Magnetoelastic Waves in Yttrium Iron Garnet
Authors: Strauss W.
Published: April 2005

Magnetoelastic rf pulses with magnetically controlled echo time have been observed in a rod of yttrium iron garnet. Data were taken at room temperature in the frequency interval 0.5 to 3.3 Gc/sec with power input in the milliwatt range. Excitation and detection was accomplished by placing a wire antenna near an optically flat end-face of the rod. A nonuniform internal magnetic field was obtained by applying a steady, uniform external field parallel to the rod axis. The frequency-time-magnetic field characteristics have been measured. The behavior of these pulses can be explained in terms of a magnetoelastic disturbance traveling along the rod axis. It originates at that position along the axis where ωc=γHi. From there the disturbance travels to the nearer polished surface where it is reflected. On arrival back at the launch site a fraction of the energy is detected and the remainder reflected for another round trip. The process is repeated several times to give rise to a pulse sequence.
Ferromagnetism in Rare-Earth Group VA and VIA Compounds with Th3P4 Structure
Authors: Holtzberg F. , McGuire T. R. , Methfessel S. , Suits J. C.
Published: April 2005

The bcc structure I4̄3d−Td6(Th3P4) occurs as a defect structure in 2:3 compounds of rare-earth elements with S, Se, and Te, or as an inverted structure in 4:3 compounds with group VA elements. The structural, electric, and magnetic properties of the metallic 4:3 compounds and the 2:3 rare-earth semiconductors have been investigated with specific reference to gadolinium, for which the S ground state gives the minimum crystal field effect.

Gd4Bi3 and Gd4Sb3 are both ferromagnetic with a saturation magnetization obeying the spin-wave T32 law up to 0.8 of the Curie temperature. The Curie temperature Tc varies in the solid solution system Gd4Sb3– Gd4Bi3 with composition from 260° to 340°K. The semiconducting compound Gd2Se3(ρRT=3 Ω cm) has been found to be antiferromagnetic below TN=6°K. Solution of Gd in the holes of the defect Th3P4 structure decreases the electrical resistivity without a measurable variation of lattice constant (a0=8.718 Å). With increasing conductivity the material changes from antiferromagnetic to ferromagnetic. At the composition Gd2.1Se2.9 the Curie temperature is Tc=80°K with ρRT=1.4×10−3 Ω cm. The relation between Curie temperature and electrical resistivity has been examined by introducing the same spin concentration into Gd2Se3 by Eu2+ doping. The semiconductor Eu0.5Gd1.6Se2.9 is paramagnetic. However, Y0.5Gd1.6Se2.9 has low resistivity and is ferromagnetic below Tc=47°K.
Magnetic Structure of Neodymium
Authors: Moon R. M. , Cable J. W. , Koehler W. C.
Published: April 2005

Neutron diffraction measurements have been made on a single crystal of neodymium at temperatures between 1.6° and 20°K. The onset of magnetic ordering occurs at 19°K and the magnetic structure changes at 7.5°K. The crystal structure is hexagonal with a four-layer stacking sequence of type ABAC. Thus, alternate layers have different nearest-neighbor environments, either hexagonal or face-centered cubic. The main features of the diffraction pattern can be interpreted on the basis of an approximate model in which the hexagonal sites order at 19°K with an antiferromagnetic arrangement between alternate hexagonal layers and with a sinusoidal modulation within each layer. The propagation vector for this modulation and the direction of the magnetic moments are both in the basal plane along a b1 reciprocal lattice vector. The magnitude of the propagation vector changes from 0.13 b1 at 18°K to 0.11 b1 at 7.5°K. The cubic sites order at 7.5°K with a similar structure, except that the propagation vector is 0.15 b1 and the moments are in the basal plane at an angle of 30° from b1. The amplitude of the modulated moments is 2.3±0.2 Bohr magnetons for the hexagonal sites and 1.8±0.2 Bohr magnetons for the cubic sites. This model fails to account for all the observed intensities but may be improved by adding a small modulated moment on the cubic sites in the upper temperature region which is shifted in phase by ½π from the modulation in the hexagonal layers, and by allowing the hexagonal moments to deviate slightly from the b1 direction.
Neutron Diffraction Investigation of a Gadolinium Single Crystal
Authors: Will G. , Nathans R. , Alperin H. A.
Published: April 2005

A single-crystal disk of Gd cut parallel to (00.1) has been studied in zero magnetic field. A careful search along and perpendicular to the c* axis in the neighborhood of the (00.2) reflection has failed to reveal any satellites in the temperature range 77° to 290°K. Thus unlike the rare-earth elements from Tb to Tm, gadolinium is a normal ferromagnet. Above 248°K, the moment is aligned along the c axis. Below this temperature, the moments make an angle with the c axis which reaches a maximum of 75° at 195°K and approaches 30° at 4°K. The coherent nuclear scattering amplitude has been estimated by scaling the nuclear scattering to the magnetic scattering in the (00.2) reflection. The result is |b|=1.5±0.2×10−12 cm.
Galvanomagnetic Properties of Ferromagnetic Uranium Monosulfide
Authors: Kanter Manuel A. , Kazmierowicz Casimir W.
Published: April 2005

Uranium monosulfide, a high-melting-point compound (2740°K) with a NaCl structure has been found to be ferromagnetic with a Curie point at 180°K and a saturation magnetic moment of 1.02 Bohr magnetons per atom at 0°K. Resistivity, magnetoresistance, and Hall effect measurements were made in the temperature range, 4.2°–360°K, so that these properties could be measured in the ferromagnetic and the paramagnetic solids. Sintered polycrystalline samples were used.

The electrical resistivity was found to be about a hundred times larger in US than in the common ferromagnetic metals but the temperature dependence was similar showing an abnormal decrease below the Curie point. The magnetoresistance was found to be negative with a sharp minimum at the Curie point. Study of the Hall effect revealed that two Hall coefficients could be identified as in the transition metals. The extraordinary Hall coefficient related to the magnetization was found to vary as the 2.1 power of the resistivity in reasonable agreement with previous theories of this effect. The ordinary Hall coefficient related to the applied field was found to be positive and temperature-dependent with a maximum at the Curie point, whereas in the ferromagnetic metals, the Hall coefficient is found to be temperature-independent with the exception of an anomalous behavior near the Curie point. A similar anomaly is observed in US which occurs over a much wider temperature range than in the common ferromagnetic metals. The effective carrier concentration evaluated from the ordinary Hall coefficient is 0.45 holes per U atom at absolute zero.

These results can be correlated with a band picture based on overlapping 7s and 5f bands, where the states in the broad 7s band contribute the major conductivity whereas the magnetic behavior is due to the unpaired spins of electrons in the narrow 5f band. Equilibrium between the bands requires a redistribution of electrons between them as the temperature varies giving rise to the observed temperature dependence of the galvanomagnetic properties. Similar measurements on isostructural ThS and UP and their solutions with US will provide a critical test of this band model.
Ferrimagnetic Garnets Containing Pentavalent Vanadium
Authors: Geller S. , Espinosa G. P. , Williams H. J. , Sherwood R. C. , Nesbitt E. A.
Published: April 2005

In a recent publication, magnetic data were reported on the newly discovered garnet {Ca3}[Fe2](Fe1.5V1.5)O12. In this paper, magnetic and crystallographic data on garnets in the systems {M3−2xCa2x} [Fe2](Fe3−xVx)O12, M≡Y or Bi, are reported. It appears that for all values of x, 0<x≤1.5, Curie temperatures are higher than would have been expected. Up to x≅0.7, the Curie temperatures are equal to or slightly greater than that of yttrium iron garnet itself, then decrease gradually to 493°K for {Ca3}[Fe2](Fe1.5V1.5)O12. Garnets in the system {Bi3−2xCa2x} [Fe2](Fe3−xVx)O12 with 1.5>x>0.8 exist. The magnetic behavior of the garnet {Bi0.5Ca2.5}[Fe2](Fe1.75V1.25)O12 is essentially the same as that of the yttrium analog. Pentavalent vanadium substitution thus provides lower moment garnets with high Curie temperatures and, including Bi3+ ion substitution, ferrimagnetic garnets not containing rare earths or yttrium.

The full-length paper with the above title has been published.
Differential Thermal Analysis and Mössbauer Studies in Rare-Earth Orthoferrites
Authors: Eibschütz M. , Gorodetsky G. , Shtrikman S. , Treves D.
Published: April 2005

Curie temperatures of 14 different orthoferrites with the chemical formula RFeO3, (R = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were measured by differential thermal analysis. Hyperfine interactions of the Fe57 nucleus in the same materials were determined from their Mössbauer spectra. The quadrupole splittings (except for Sm), isomer shifts, Curie temperatures, and internal fields vary regularly with the ionic radius of R.
Room-Temperature Resistivity of Mo-Nb and Mo-Re Alloys Containing One Percent Iron
Authors: Sarachik Myriam P.
Published: April 2005

The room temperature resistivity has been measured for a series of molybdenum-niobium and molybdenum-rhenium alloys, with and without 1% iron as solute. A maximum in the scattering due to the iron is found near the alloy composition for which a localized moment first appears. The results are interpreted in the light of current theories of localized moments.
A Basic Theory of the Mercury Cathode Spot
Authors: Hull A. W.
Published: April 2005

Most writers about the cathode spot have concluded that it is too complicated for valid conclusions. There is presented here a simple theory, which can be called basic, since it is founded on the single assumption that the electron emission is field emission.

It follows immediately from this assumption that the positive ion current density must be about 5×105 A/cm2 to supply the necessary field of 2.7×107 V/cm; and this, with an allowance of 20 electrons per ion for the two-stage ionization, determines an electron current density of 107 A/cm2.

This large ion current and the resultant heating of the spot precludes an energy balance, which would require temperatures and pressures far above the critical to dissipate the heat by conduction and evaporation.

Such a balance would never be reached, however, because of a mechanical balance between the forces of surface tension and vapor pressure, which limits the pressure and temperature to much lower values; namely a pressure of about 1 atm and the temperature of the order of 400°C. The balance is given by the simple equation p=(2γ/r) dyn/cm2,where γ is the surface tension in dyn/cm, and r the radius of the spot in cm. A table is given for the calculated pressure and temperature for different currents.

This maximum temperature determines the velocity of (random) motion of the spot, which is just its diameter divided by the time to heat a new spot to this temperature. The calculated velocities are included in the table.

Retrograde motion of the spot in a magnetic field is explained by a drift of slow ``residual'' electrons parallel to the surface in the ``correct'' direction, thus weakening the electric field drawing ions to the surface. A theory of drift of slow electrons by Tonks, makes possible a calculation of the drift angle, which determines the change from retrograde to ``correct'' motion as the magnetic field and vapor pressure are changed. The calculated values are in good agreement with experiment.

There are no measurements of pressure on a free spot, but the theory predicts correctly the height to which mercury droplets are thrown, assuming the erupted droplets to be the same diameter as the spot.

Observed pressures for anchored spots are much higher, but these depend on an entirely different mechanism.

The observed velocities of retrograde motion are much less than those calculated; but it is pointed out that the motion may be largely random, rather than in a straight line, which would make agreement with the theory possible.

Evidence is given that the limiting current of 30 A per spot is due to the IR potential drop in the mercury, which leaves insufficient energy for ionization if this current is exceeded.

A few values of pressure and temperature are calculated for other low-boiling-point metal arcs, assuming that the same theory applies to them.
Laser Action in a Flux-Grown Ruby
Authors: Nelson D. F. , Remeika J. P.
Published: April 2005

A method of growing very perfect ruby crystals by slow cooling of a PbO (B2O3)X flux doped with Al2O3 and Cr2O3 is described. A crystal grown by this method has been operated as a laser with its natural crystal faces used as feedback surfaces. Interferometry through these surfaces showed that the optical path length between the feedback faces varied only about λ/10 for red light over the entire face. The angles of laser emission high above threshold agreed accurately with those predicted for a Fabry-Perot cavity. Near threshold the output consisted of a very regular damped oscillation of the Statz-deMars type that was completely linearly polarized. A little farther above threshold a second train of oscillations was also present and was polarized at 90° to the first train. A formula for the laser threshold dependence on temperature was derived. A comparison of the model with measurements made between 90° and 305°K allowed a determination of the cavity loss under laser operation. With multilayer dielectric film reflectors a loss of less than 1% per pass was found, the bulk of which could be accounted for by known transmission and absorption losses in the end films.
Effect of ``Rougher-than-Rough'' Surfaces on Molecular Flow through Short Ducts
Authors: Davis Donald H. , Levenson Leonard L. , Milleron Norman
Published: April 2005

Gaede reported lower molecular flow rates through some tubes than expected if he assumed the walls were 100% diffuse reflecting. He conjectured that back reflection from surface asperities might be responsible. We support Gaede's intuitive guess, having measured flow rates and applied the Monte Carlo calculational method to geometrical models. Our results show that: (1) surface finishes from ½ to 64 μ in. (0.013 to 1.6 μ) roughness yield flow rates from 5% above to 6% below the diffuse wall prediction; (2) specular reflection can account for the 5% higher value; (3) for cylinders with internal corrugations, fins and threads of groove depth from 0.1 to 15% of the minimum tube radius and included angle between 30° and 60°, conductance is from 15 to 20% lower than conductance assuming diffuse reflection from smooth walls. Experiment and calculation agree within ±4%.
Pressure Dependence of Creep in White Phosphorus
Authors: DeVries K. L. , Gibbs Peter , Miles H. , Staten H. S.
Published: April 2005

Bending creep in white phosphorus is reported at 27° and 41°C at pressures to 6 kbar. The activation volume for creep is approximately 50.3×10−24 cm3/atom, which is about the same as that determined by Nachtrieb and Lawson for self-diffusion.
Calculations of the Conductivity of a Medium Containing Cylindrical Inclusions
Authors: Keller Herbert B. , Sachs David
Published: April 2005

Finite difference calculations of the conductivity of an infinite medium containing a square array of perfectly conducting cylindrical inclusions are reported. For dense packing the results agree with and yield an estimate of the next term in an expansion derived by J. B. Keller. For sparse and intermediate packing the calculations are in excellent agreement with a formula derived by Rayleigh and improved by Runge.
Refractive Index of ZnSe, ZnTe, and CdTe
Authors: Marple D. T. F.
Published: April 2005

Refractive indexes of ZnSe, ZnTe, and CdTe were obtained from prism refraction data and are reported for a series of wavelengths from 2.5 μ to the short-wave transmission limits set by the band gaps. The results were fitted with the standard formula: n2=A +[Bλ2/(λ2−c2)] where n is the refractive index and λ is the wavelength in microns. For ZnSe the best values of the parameters are A=4.00, B=1.90, and c2=0.113; for ZnTe, A=4.27, B=3.01, and c2=0.142; and for CdTe, A=5.68, B=1.53, and c2=0.366. Possible causes for the discrepancies between the present results and earlier data are discussed.
Ferrimagnetic Garnets Containing Pentavalent Antimony
Authors: Geller S. , Williams H. J. , Espinosa G. P. , Sherwood R. C.
Published: April 2005

Pentavalent antimony may be substituted for Fe3+ ions in iron garnets when appropriate electrostatic compensation is made. It appears that the Sb5+ ion prefers octahedral sites exclusively. Magnetic and crystallographic data are reported on the systems {Y3−2xCa2x} [SbxFe2−x](Fe3)O12 and {Ca3} [SbxFe2−x]− (Fe1.5+xV1.5−x)O12, the latter is the system obtained from solid solutions between the end member {Ca3} [Sb1.5Fe0.5](Fe3)O12 of the former and the previously reported ferrimagnetic garnet {Ca3}[Fe2]− (Fe1.5V1.5]O12. Magnetic and crystallographic data are also given on four other garnets involving substitution of Sb5+ ions. Results are compared with those from systems in which di-, tri-, and tetravalent nonmagnetic ions are substituted for Fe3+ ions in YIG (yttrium iron garnet). An important conclusion is the corroboration of the idea that the particular nonmagnetic ion substituent affects the magnetic behavior, probably as a result of the nature of the chemical bonding of the particular ion. Probably most interesting is the result that the Sb5+ ion provides additional ferrimagnetic garnets not containing rare earths or yttrium.
Getter Sputtering for the Preparation of Thin Films of Superconducting Elements and Compounds
Authors: Theuerer H. C. , Hauser J. J.
Published: April 2005

A new sputtering technique which eliminates the need for ultrahigh vacuums in preparing thin films of materials sensitive to gaseous impurities is described. This technique uses the gettering action of part of the sputtered atoms to produce an atmosphere within an anode can very low in reactive gases such as O2 and N2. In consequence, contamination by such interstitial impurities is prevented during deposition. The method has been successfully used for the preparation of superconducting films of materials such as Ta, Nb, V3Si, V3Ge, and V3Ga. This technique in conventional vacuum equipment produces films of pure elements with superconducting properties comparable to those of bulk material. The method should be applicable also to the preparation of magnetic alloy films and epitaxial semiconductor films where contamination by reactive gases has been a problem.
An Explanation for the Effect of Ferromagnetism upon Atomic Diffusion
Authors: Borg R. J.
Published: April 2005

An explanation for the effect of ferromagnetism upon atomic diffusion is based upon the change in elastic properties corresponding to the degree of magnetic order. The unusual temperature dependence of D, the diffusion coefficient, in the vicinity of Tc, the Curie temperature, can be reconciled with recent measurements of the shear moduli by using the Zener model for diffusion.
Evaporated Metallic Contacts to Conducting Cadmium Sulfide Single Crystals
Authors: Goodman Alvin M.
Published: April 2005

Vapor deposited metallic contacts (area =̇1 mm2) have been made to oriented conducting cadmium sulfide crystals. The metals employed were Al, Ag, Cu, Pd, Au, and Pt. The electrical properties of these contacts have been studied by measurements of: (1) differential capacitance as a function of bias voltage, (2) current-voltage characteristics, and (3) spectral variation of photoemission from the metal into the cadmium sulfide. These measurements have been analyzed to yield values of Δφ (work function of the metal with respect to the cadmium sulfide at the contact) that are reproducible from contact to contact for a given metal and different for different metals. The relationship between Δφ, φm (work function of the metal in vacuum), and χ (semiconductor electron affinity), Δφ=φm−χ, is confirmed consistent with χ=̇4.0 volts for cadmium sulfide.
Photoelectronic Properties of Imperfections in Cadmium Sulfo-Selenide Solid Solutions
Authors: Bube Richard H.
Published: April 2005

The electron and/or hole ionization energy of imperfections in single crystals of cadmium sulfo-selenide solid solutions have been measured by a variety of photoelectronic techniques including optical absorption, optical quenching of photoconductivity, thermal quenching of photoconductivity, photoconductivity decay, and thermally stimulated conductivity. Both the optical and thermal hole ionization energy of sensitizing center acceptors undergo an abrupt decrease from a value characteristic of cadmium sulfide (∼1 eV) to a value characteristic of cadmium selenide (∼0.6 eV) between 30% and 50% cadmium selenide. The same transition is observed as an abrupt increase in the energy of the imperfection absorption edge, corresponding to the optical electron ionization energy of these centers. The electron ionization energy of electron traps varies approximately proportionally to the band gap throughout the solid solution range.
Comparison of the Photoelectric Properties of Cleaved, Heated, and Sputtered Silicon Surfaces
Authors: Allen F. G. , Gobeli G. W.
Published: April 2005

The properly cleaved silicon surface exhibits highly reproducible photoelectric properties, and is known from electron diffraction results to be of high structural perfection. The surface-atom rearrangement that occurs upon heating the cleaved (111) surface to 1000°K in vacuum causes marked changes in the electrical properties of the surface. The work function of a high-resistivity p-type sample which has the energy bands flat up to the surface in the cleaved state drops from 4.8 to 4.6 eV and the photoelectric threshold drops from ∼5.15 to ∼4.6 eV. The kinetic-energy distribution of emitted electrons and the yield spectrum indicate at least two distinct groups of photoelectrons in both the cleaved and heated samples. The principal group, of lower energy, is attributed to a direct optical transition in both cases. In the heated samples, the group of high-energy electrons is further separated from the low group than in the cleaved samples, and originates from just below the Fermi level at the surface. This group is tentatively ascribed to emission from surface states that have moved up to the Fermi level in the forbidden gap. The yield spectrum for a sputtered and annealed (111) silicon surface is closely similar to that for the cleaved and heated samples, as expected from the fact that in low-energy electron diffraction both types of surfaces have the same atomic arrangement. Changes in photoemission during cleaning show that ∼95% of the photoelectrons are trapped by an oxide layer ∼20 Å thick.
Transit-Time Considerations in p—i—n Diodes
Authors: Lucovsky G. , Schwarz R. F. , Emmons R. B.
Published: April 2005

Linear equations for the carrier concentrations and photocurrent density in the i region of a p—i—n photodiode have been obtained. The frequency response of this photodiode has been calculated taking account of the difference in mobility of the carriers, and of the nonuniform generation of carriers in the i region. For high frequencies, the frequency response of the diode is largely dependent on the faster moving of the two carriers. For a Si p—i—n photodiode using ruby laser light, a transit-time limitation of 5 Gc/sec has been previously estimated by the authors. On the basis of the above analysis, the transit time limitation is estimated to be 15 Gc/sec. In both cases these estimates refer to the frequency of the half-power point.
Incomplete Liquid Mixing in Crystal Growth from the Melt
Authors: Wilcox W. R.
Published: April 2005

The boundary-layer treatment of Burton, Prim, and Slichter for prediction of segregation in crystal growth from the melt is extended to arbitrary binary solid/liquid equilibrium phase behavior. The validity of the quasi steady-state approach is examined by derivation of the initial transient. In many cases this transient is appreciable and must be considered for accurate predictions. Eigenvalues for calculation of the transient are given, along with a sample calculation.
Double-Cantilever Cleavage Mode of Crack Propagation
Authors: Gillis Peter P. , Gilman J. J.
Published: April 2005

The quantitative cleavage method for determining specific surface energies of solids is subject to several possible sources of error. Some of these are investigated analytically in this study, and a general expression for the surface energy is derived from beam theory for a linearly elastic material. The exact equation of motion for the propagating crack is derived but not solved.

Errors associated with each term of the general expression are assessed. The ratio of shear to bending strain energy is small if the initial crack length is long compared with the specimen depth. The term arising from strains in the specimen past the tip of the crack is not developed, but is estimated; and a procedure is outlined for determining this term experimentally.

Comparison of simple beam theory with more exact elasticity theory shows that in the main spans the difference is small because it involves only the shear strain energy. Also, restriction of anticlastic curvature near the crack tip is unimportant if the initial crack length is long compared with the specimen width. Elastic anisotropy is unimportant when shear can be neglected, provided the appropriate modulus is used.

For nonlinear elastic material, as the crack propagates a small amount, the work increment is either zero or double the strain energy increment. A surface energy expression is developed in terms of Timoshenko's ``reduced modulus,'' and upper and lower bounds are fixed.

For plastic materials the analysis is based on pseudoinstantaneous plastic response. Justification of this assumption is difficult to defend or deny. Therefore, an important conclusion is that whenever possible specimens should be designed to remain grossly within the elastic limit of the material.

Superposition of large axial forces is a potential source of large errors in surface energy determinations, and possible eccentricities in the application of such forces makes even the sign of these errors difficult to determine. Hence, this method for stabilizing the crack plane is not recommended.
Two Photomechanical Effects in Alkali Halide Crystals
Authors: Nadeau J. S.
Published: April 2005

Two photomechanical effects, observed in alkali halide crystals containing color centers, appear as sudden reversible changes in flow stress when a crystal is illuminated. Both effects are related to optical transitions of the F center. In potassium chloride, intensely illuminated at 175°K, hardening appears to be caused by the F → F′ process. Below 80°K, in KCl, even more severe hardening is caused upon illumination, by transport of the F-center electron to an unspecified trap lying very close to the conduction band; decay of the hardening after extinction of the exciting light requires several seconds and may be caused by dislocation—point defect interactions.

The effects have been observed in nine of the alkali halides. Flow stress increases and decreases were both observed, depending upon the particular alkali halide.
Antiphase Domains in Ordered Au3Cu Alloys
Authors: Toth Robert S. , Sato Hiroshi
Published: April 2005

Alloys having compositions from 42%−9% Cu in the Cu-Au system were investigated to determine the nature of the antiphase structures and the range of the ordered Au3Cu structure in this region. The single-crystal thin-film technique was used to prepare the specimens and the structure was determined by electron diffraction. The ordered Au3Cu I structure exists as an equilibrium phase from 38.5%−9% Cu. Unlike the Cu3Au and CuAu alloys, however, periodic antiphase structures are not observed as an equilibrium phase in these alloys. Increasing the electron-atom ratio by the addition of a third element, for example, Al, results in the formation of a periodic antiphase structures as predicted. It is shown that the low ordering temperature is responsible for the failure of a periodic antiphase structure to appear in these alloys.
Future Developments in Large Magnetic Film Memories
Authors: Raffel Jack I.
Published: April 2005

Some judgments are formulated about memory organization, fabrication techniques and cell structures which are generally applicable to improving the speed-cost ratio of static magnetic storage devices.

More specifically, for magnetic films, techniques for realizing simultaneously high bit density and simple fabrication are discussed.

Based on very rough estimates, it is proposed that for a million-word memory, a cost reduction of almost two orders of magnitude over present day stores with speeds of approximately one microsecond or less should be feasible with films.

Alternative cell configurations and areas of engineering compromise are discussed. Experimental results with etched cells having dimensions as small as 2 mils (0.05 mm) for both quasiclosed and open structures have been obtained.

Both multiword readout and a method for sharing sense amplifiers by ``band switching'' are considered.
Magnetic Behavior of High-Field Superconductors
Authors: Bean Charles P.
Published: April 2005

Homogeneous superconductors have reversible magnetic properties. We distinguish two types of superconductors, type I and type II. The type I superconductor (most pure superconducting elements are of this type) has a particularly simple magnetic behavior.1 In a macroscopic specimen, the flux density is zero for fields less than the critical field, Hc, that marks the limit of the superconducting state. Above this field the specimen has all the properties of a normal metal including the property that the flux density is essentially equal to the applied field. So, in summary, the type I superconductor is either completely superconducting or completely normal. (This statement is strictly true only for a long thin specimen in a field that is parallel to the axis of the specimen. In other geometries one finds a gross mixture of superconducting and normal regions called the intermediate state that is created by the field concentrations associated with specimen shape.) In recent years it has been appreciated that there is another class of superconductor—usually an alloy or compound—in which the flux in a bulk specimen is completely excluded for fields less than Hc1, but above this field flux penetration is partial and increases with applied field until flux penetration is complete at an upper critical field, Hc2. Since this field is generally larger than the equivalent Hc of type I superconductor, these type II superconductors are known as high-field superconductors. The region between Hc1 and Hc2 is known as the mixed state which is not to be confused with the shape-dependent intermediate state mentioned earlier.

The present conception of the mixed state2 pictures the flux as entering in the form of quantized current vortices. The total flux contained in each vortex is 2×10−7 G-cm2. In equilibrium these vortices repel one another to form a lattice that compresses as the field is increased from Hc1 to Hc2 and finally all flux variation smoothly disappears at Hc2. Experimental magnetization curves on homogeneous alloys show good agreement with this theory.3

If the type II is inhomogeneous, there may be impediments to the motion of these flux lines. In this event there will be a gradient of flux as the flux is driven into the specimen.4 This gradient of flux lines is equivalent to a macroscopic current density by Ampere's law, curl H=4πJ/10.4 This behavior allows one to calculate the magnetic behavior of these superconductors in terms of only one parameter, the critical current density, Jc(H)5—the same critical current density that is measured in current transport measurements. The magnetic behavior includes size-dependent magnetization and a hysteresis loop that is the precise diamagnetic equivalent of the Rayleigh hysteresis loop for ferromagnets.
Coupled Biaxial Films
Authors: Chang Hsu
Published: April 2005

Biaxial films were proposed by Pugh for storage elements of a noncoincident memory. In this paper, it is demonstrated that two identical uniaxial films with their easy axes at a right angle and driven by interposed striplines that carry currents also exhibit biaxial properties.
A Multilayer Dielectric- and Magnetic-Film Memory Cell Designed for Optical Read Out
Authors: Smith D. O.
Published: April 2005

A 4×4 matrix formulation of optical reflection from multilayer dielectric and magnetic films has been developed and applied to a structure consisting of a dielectric film on top of a magnetic film all on a mirror substrate. The dielectric thickness d1 is specified by tan (n1β12πd1/λ0) = (1/n1β1) (λ0/2πd), where λ0 is the free-space wavelength, n1 the index of refraction of the dielectric, β1 the cosine of the angle of propagation in the dielectric (measured to the film normal), and d the thickness of the magnetic film (d≃200 Å). The longitudinal Kerr reflection coefficient k⊥ = H∥r/H⊥t, where r and t refer to reflected and transmitted (incident) waves, and ∥ and ⊥ to the states of polarization, is calculated under the assumption that k1«1 to be k⊥ = i2γ0n12 (2πd/λ0) p, where γ0≃1 is the cosine of the angle of light incidence (measured to the film plane), and p is the gyromagnetic constant. In principle for large n1 the upper limit on |k⊥| is determined only by the breakdown of the assumption k⊥«1. For n1≃3, d=200 Å, λ0=1 μ, and p=5×10−2 (Fe at 1 μ), the energy-conversion efficiency w =|k⊥|≃10−4.
Hexagonal Ferrite Isolators
Authors: Taft D. R.
Published: April 2005

Waveguide bandwidth isolators requiring virtually no externally applied magnetic field have been developed for the millimeter wave frequency range. These ferrimagnetic resonance-type devices utilize highly anisotropic uniaxial hexagonal ferrites. The specific ferrite compounds used are from the two families BaO·2NiO·ΔAl2O3 · (8-Δ) Fe2O3 and SrO·δAl2O3· (6-δ) Fe2O3 denoted Ni2W (ΔAl) and SrM (δAl), respectively. The substitution variables Δ and δ were adjusted to yield different materials whose effective magnetic anisotropy fields were appropriately spaced over the range 16 to 30 kOe. This spacing permitted their use in isolator designs throughout the frequency range 50 to 90 Gc/sec. Five materials from the Ni2W(ΔAl) family were used to cover the frequency range 50 to 60 Gc/sec and 12 materials from the SrM(δAl) family covered the range 60 to 90 Gc/sec. Pertinent electrical properties of these materials are reported as well as techniques essential to their successful application in the isolator structure. Waveguide bandwidth isolators using these materials were developed for the bands 50 to 75 and 60 to 90 Gc/sec.
An Explosive-Driven High-Field System for Physics Applications
Authors: Caird R. S. , Garn W. B. , Thomson D. B. , Fowler C. M.
Published: April 2005

A simple explosive-driven flux compression system is described for producing magnetic fields in the MG range. The flux-trapping device is a seamless hollow stainless steel cylinder driven by a ring of explosive. The initial field is introduced by a coil pair supplied by a 90-kJ capacitor bank. The assembly is readily evacuated. During implosion, the experimental volume is free of objectionable debris and asymmetries. Peak fields of 1.2 and 4 MG are achieved in working diameters of 8.9 and 3.2 mm, respectively. The usable length is about 15 mm at these fields. Several possible applications are mentioned.
Spin-Wave Energies and Exchange Parameters in Iron-Nickel Alloys
Authors: Hatherly M. , Hirakawa K. , Lowde R. D. , Mallett J. F. , Stringfellow M. W. , Torrie B. H.
Published: April 2005

The energies of long-wavelength spin waves in iron-nickel alloys have been measured as a function of composition by a neutron small-angle-scattering technique. The behavior of the composition dependence can be explained in terms of a simple model invoking long-range interaction functions J(r) between the three different types of atom pair: Fe–Fe; Fe–Ni; and Ni–Ni. There is evidence that on the bcc lattice the iron-nickel interaction J(r) changes sign from +ve to -ve as a function of distance. Between Fe–Fe pairs on a fcc lattice, the ``exchange integral'' as normally defined is −8±2 MeV, consistent with other indications that fcc iron is antiferromagnetic.
Magnetization of Permalloy at Low Temperatures
Authors: Argyle B. E. , Charap S. H.
Published: April 2005

Pyromagnetic measurements of the magnetization of a single-crystal sphere of Permalloy (79.65 Ni-20.35 Fe by weight) in the range 4.2°–100°K and with applied fields of 4, 9, and 14 kOe parallel to the [111] crystal axis are reported and interpreted in terms of spin-wave theory. The spin-wave energy gap obeys the theoretical expression in terms of internal applied field, magnetocrystalline anisotropy field (negligible), and average spin-wave demagnetizing field. The coefficients appropriate to zero gap are C = (7.6±0.1)×10−6 deg−3/2 for the T3/2 term and D/C≤±0.2×10−3 deg−1 for the T5/2 term. The analysis of the data is made using a new graphical method which displays visually the quality of fit to the theory. The C value implies (JS)eff/kB=134°K in good agreement with independent determinations of the spin-wave dispersion parameter.
Linewidths in Ferromagnetic Thin Films
Authors: Wigen P. E. , Shanabarger M. R.
Published: April 2005

An inhomogeneity in the magnetization of thin ferromagnetic films provides a mechanism for two-magnon scattering that contributes to the spin-wave resonance linewidth of thin ferromagnetic metal films.1 A normal (perpendicular) variation in the internal field has previously been assumed to explain the spinwave resonance properties of thin films.2–4 A variation of the magnetization in the plane of the film produces an inhomogeneously broadened linewidth. Since the inhomogeneity is much smaller than the average magnetization of the material, dipole forces decrease the inhomogeneous broadening of the resonance line.5 Experimental results are in good agreement with the theory when eddy current losses are included and account for an inhomogeneity in the plane of the film that is of the same order of magnitude as the normal inhomogeneity. As the film normal is rotated with respect to the magnetic field direction, the critical angle is approached at which the resonance conditions are the same throughout the film and the spins precess at a common frequency. At this angle the planar inhomogeneity is not effective in broadening the excited mode. This effect is indicated in the data by a minimum in the frequency linewidth at this angle. This calculation is consistent with data obtained from Permalloy, cobalt, and nickel films at 10 and 15 Gc/sec.
Inhomogeneity in the Magnitude of the Anisotropy Field in Thin Nickel-Iron Films
Authors: Oredson H. N. , Torok E. J.
Published: April 2005

The inhomogeneity in the magnitude of the anisotropy field of vacuum-deposited nickel-iron films has been measured as a function of film composition, inhomogeneity in composition, substrate temperature, time interval of deposition, and diameter of the film. The part of the inhomogeneity in the magnitude of Hk due to the product of the magnetostriction and the nonisotropic strain is found to be twice the part of the inhomogeneity in the direction of Hk due to this cause, as predicted by Crowther. Part of the inhomogeneity in magnitude but not in direction of Hk is attributed to nonuniformity in substrate temperature, and part to magnetocrystalline anisotropy.
Origin of Domain-Wall Creeping in Magnetic Films
Authors: Green A. , Leaver K. D. , Prutton M.
Published: April 2005

On the assumption that domain-wall creeping in thin films is associated with changes in the magnetization distribution of a wall, four mechanisms are described that may account for the wall creeping. They are discussed in relation to the available experimental evidence. Further experiments, suggested to determine the validity of the mechanisms, concern in particular the frequency dependence of creep and the coercivity of pure Néel walls.
Mechanism of Ripple Formation in Thin Films
Authors: Spain Robert Jay , Puchalska Irena B.
Published: April 2005

To test the hypothesis that magnetization ripple in thin films is due to the randomly oriented magnetocrystalline anisotropies of the individual crystallites, highly oriented iron films have been made which exhibit a marked decrease in ripple intensity. Changes in ripple intensity, produced by applying mechanical stresses so as to vary the resultant uniaxial anisotropy constant of a given sample, are consistent with the model of variations of the local easy axis direction as responsible for the formation of magnetization ripple.
Properties of Molybdenum-Permalloy Films
Authors: Ahn K. Y. , Beam W. R.
Published: April 2005

Ternary alloy films were produced by variable-ratio sequential and simultaneous two-source evaporation under conditions comparable to those of technical Permalloy film evaporation. Intrinsic film properties measured at Mo concentrations up to 6%–8% indicated reductions of M, Hc, Hk, and dispersion. At high Mo concentrations, oblique incidence produced strong anisotropies. Crystallite dimensions were substantially less than in normal Permalloy films, and increased resistance to annealing was observed.
Magnetic Properties of Ni-Fe-Cr Films
Authors: Cohen M. S.
Published: April 2005

Films of Ni-Fe-Cr were vapor deposited on heated glass substrates in vacuum. In each preparation increasing amounts of Cr were added to the original Ni-Fe source, and a fresh set of glass substrates was exposed to the vapor beam after each Cr addition. In this way, Cr contents ranging from 0% to about 5% were produced in different films in each preparation, while Ni-Fe ratios of various preparations ranged from 78% Ni, 22% Fe to 90% Ni, 10% Fe. For all Ni-Fe ratios the anisotropy field Hk, the magnetization M, and the wall coercive force Hw, decreased monotonically with Cr content, while angular dispersion and electrical resistivity ρ increased with Cr content. The variations of M and ρ with Cr content were consistent with bulk data. The empirical relation Hk=A(M-B) was found valid except for very small or very large additions of Cr; the constants A and B were independent of the initial Ni-Fe ratio but dependent on the substrate temperature. Addition of Cr always tended to make the magnetostriction more positive, regardless of the initial Ni-Fe ratio.