bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Mn55 NMR Absorption in Antiferromagnetic KMnF3
Authors: Nakamura A. , Minkiewicz V. , Portis A. M.
Published: April 2005

The direct observation of Mn55 nuclear magnetic resonance absorption in the nearly cubic antiferromagnet KMnF3 is reported. The striking features of the resonance are its unusual intensity and its strong temperature and field dependence. Both effects are associated with the strong coupling between nuclear and electronic modes in magnetic materials with low anisotropy and large nuclear magnetization. The nuclear linewidth at 4.2°K is 740 kc/sec between points of half-maximum absorption. This width is in agreement with that expected from the Suhl-Nakamura indirect coupling between nuclear spins. At lower temperatures the linewidth increases greatly, approaching nearly 3 Mc/sec at 2.1°K. This unexpected increase in linewidth is attributed to a low-temperature inhomogeneity in the antiferromagnetic excitation spectrum.
A Proton Resonance Study of the Magnetic Structure of Antiferromagnetic CoCl2·6H2O, CoBr2·6H20, NiCl2·6H2O, and NiBr2·6H2O
Authors: Spence R. D. , Middents Paul , ElSaffar Z. , Kleinberg R.
Published: April 2005

Studies of the antiferromagnetic states of CoCl2·6H2O, CoBr2·6H2O, NiCl2·6H2O, and NiBr2·6H2O by proton resonance show that their magnetic space group must be either Pc21/a or Cc2/c. The magnitudes of the local fields indicate that the Co salts belong to the former group and the Ni salts to the latter.
Magnetic Properties of Cube-Textured 6–81.3 Mo—Permalloy
Authors: Odani Yuzo
Published: April 2005

A study was made of the magnetic properties of Mo—Permalloy sheets containing 5.3%–6.8% Mo and 79.5%–82.5% Ni that had been cold rolled and annealed to obtain a nearly perfect (100)[001] texture. Square hysteresis loops were obtained only in compositions of about 81.3% Ni quenched from temperatures greater than 500°C, in hydrogen. Magnetic properties of spiral cores made of insulated 0.05 mm thick 6–81.3 Mo—Permalloy tapes were as follows: (a) When annealed at 1150°C to prevent secondary recrystallization, a square loop with μm=1200 000, μ0≤10 000, Hc=0.004 Oe, and Mr/Ms=0.92 was obtained. (b) When annealed at 1170°C, secondary recrystallization occurred; the μ0 of the core was increased to 160 000.
Influence of the Thermal and Mechanical History on the Squareness Characteristics of 4–79 Molybdenum Permalloy
Authors: Chin G. Y. , Vanskike L. L. , Andrews H. L.
Published: April 2005

A correlation was obtained between crystallographic texture and the squareness characteristics of 4–79 molybdenum Permalloy wire and tape. When cold drawn (99% RA) 2.18-mil-diam Permalloy wire was annealed at 800°C for 0–7.8 sec, 60 cps Br/Bs values (measured along the wire axis) dropped from 0.95 to 0.70. Further drawing of the annealed wires to 1.3 mil resulted in an increase of Br/Br, relative to the 2.18-mil wire, for the short-anneal (0.31 and 0.65 sec) samples and a decrease for the long-anneal (1.3 and 7.8 sec) samples. The trend was reversed when the 1.3-mil wires were roll flattened to tapes such that the direction of flow was perpendicular to the wire axis. X-ray studies indicated a strong 〈111〉 fiber texture in the cold-drawn wire and a 〈100〉+〈111〉 double texture after annealing, the ratio of 〈100〉 to 〈111〉 intensity increasing with annealing time. The tapes contained (100)[001] and (11̄0)[111]6° texture components, the intensities of which were related, respectively, to those of 〈100〉 and 〈111〉 components in the original wire. Thus it appears that drawing of a 〈111〉 wire led to increased squareness, in contrast to the 〈100〉 case; the reverse behavior, however, was exhibited in tapes roll flattened from wires of these two textures. These results were discussed in terms of the ``slip-induced directional order'' theory of Chikazumi et al.
Magnetic Properties of an Iron—Nickel Single Crystal Ordered by Neutron Bombardment
Authors: Néel L. , Pauleve J. , Pauthenet R. , Laugier J. , Dautreppe D.
Published: April 2005

It has been shown that a new ordered structure can be obtained in an Fe-Ni (50%–50%) alloy, by irradiating it with neutrons below 320°C. This ordered structure is tetragonal (AuCu type) and leads to a very high magnetic anisotropy. We have studied the magnetic properties of a single-crystal disk irradiated with neutrons at 295°C, with an applied magnetic field along the [100] direction. The x-ray superlattice lines show that after irradiation the sample is made of small ordered crystallites with their tetragonal axes distributed along a [100], [010], or [001] direction. The study of the anisotropy energy in the sample plane [011], and the magnetization curves drawn for different directions, show that this sample presents the characteristics of a uniaxial substance. But if we express, in a classical way, the anisotropy energy by K1 sin2θ+K2 sin4θ, we find experimentally K1=3.2·106 ergs/cm3 and K2=2.3·106 ergs/cm3.

This high value of K2 is not in agreement with the conception of independent crystallites. One of us (L.N.) has made a theory taking into account the exchange interaction between the crystallites which are in fact smaller than the magnetic domains. The formulas obtained in this way give a good agreement with the experimental results.
Irradiation of Iron and 5–79 Mo Permalloy with 2-MeV Electrons
Authors: Gordon D. I. , Sery R. S.
Published: April 2005

Large changes in the structure-sensitive magnetic properties of bulk polycrystalline 5–79 Mo Permalloy resulted from irradiation with 2-MeV electrons at ∼1017 electrons/cm2 at temperatures ranging from 60° to 170°C. These changes showed an approximately linear dependence on sample thickness from 0.10 to 0.25 mm. In addition, extreme rectangularities in the magnetization curves and hysteresis loops were obtained. For example, the maximum slope of the magnetization curve for a 0.10-mm sample increased from ΔB/ΔH=0.3×106 to ΔB/ΔH=4.3×106. This unusual steepness is evidence of the effectiveness of electron irradiation in influencing order in 5–79 Mo Permalloy at temperatures well below the ordering temperature, and without an applied magnetic field.

Iron, irradiated under the same conditions, showed no changes in its magnetic properties.

The range of 2-MeV electrons in these materials is ∼1.3 mm, well beyond the maximum sample thickness used. The calculated fractional number of atoms displaced is ∼5.3×10−6, which decreases slightly with thickness, unless one considers the difference between the actual path length of the electron in the sample (due to multiple scattering) and the actual sample thickness. If this difference between the average path length and sample thickness is calculated according to the theory of Yang, then the fractional number of atoms displaced increases linearly with sample thickness, in agreement with the thickness dependence of the radiation induced magnetic properties changes observed.
Intrinsic Ferromagnetic Resonance Linewidth in Metal Single Crystals
Authors: Frait Zdenek , Heinrich Bretislav
Published: April 2005

The results of the measurements of the ferromagnetic resonance (FMR) linewidth in iron, fcc cobalt, nickel, silicon iron, and Permalloy single crystals at room temperature at 9.2 and 36.2 Gc/sec are given in the present paper. In these cases (except nickel) the linewidth can be fully explained by the exchange broadening due to skin effect and surface spin pinning. The assumed values of the surface anisotropy are not inconsistent with the values determined from spin-wave resonance of thin films. The hypothesis, that the intrinsic FMR linewidth of bulk metals (i.e., the linewidth measured in a both statically and dynamically homogeneously magnetized material) should be no more than several Oe (at least in some single crystals) is supported by the frequency dependence of FMR linewidth.
Effect of Cold Rolling on Magnetization Reversal of High-Purity Nickel Tapes
Authors: Hirsch A. A.
Published: April 2005

Dynamic magnetoresistance hysteresis loops were used for investigation of the magnetization reversal in cold-rolled tapes of high-purity nickel. The tapes were prepared by unidirectional rolling as well as by rolling with reversing tape end for end between passes. The loops were cycled in the range ±4500 Oe with a variety of frequencies f from 0.005 to 0.1 cps in the wide interval of temperatures from 297° to 4.2°K. When the magnetization field was transverse to the rolling axis, the coercive force could be expressed by Hc = A (lnf−lnf0)/T½, where A and f0 are in general dependent on the reduction of the tape thickness, and vary slightly with the temperature T. Such a relation may be related to a magnetization reversal occuring through a process of reorientation of spins, which can be described as a temperature-activated domain-wall relaxation. The magnetoresistance loops of the samples made by unidirectional cold rolling were asymmetric when they were performed by applying simultaneously two crossed magnetic fields, one ac and the other dc. A magnetic uniaxial anisotropy induced by this rolling seems to be responsible for the observed asymmetry, a possible mechanism for this being the deformation of crystals by slips.
Flux Reversal at Low Temperatures
Authors: Humphrey Floyd B.
Published: April 2005

Fast flux reversal in thin (2000 Å) Permalloy films has been observed at 77° and 4°K and compared to room temperature. The inverse of the reversal time as a function of drive field with initial angle as a parameter was plotted. The switching coefficient Sw of the low-drive region increased threefold which is inconsistent with a simple, eddy-current-damped domain wall motion model since the conductivity changed only 17% over the same range. The switching coefficient for the intermediate-drive region is essentially constant to 77°K and then increases as the temperature is reduced in a manner inconsistent with an intrinsically damped nonuniform rotational mechanism. The thresholds in this region doubled, as did the anisotropy field HK between 296° and 4°K. The high-drive region does not change with temperature consistent with a coherent rotational model.
Contribution of Line Defects to the Parasitic Paramagnetism in the Approach to Magnetic Saturation
Authors: Aharoni Amikam
Published: April 2005

For one-dimensional plane defects, a parasitic paramagnetism is obtained if in the near vicinity of each defect there are defects of opposite sign. The two-dimensional problem of a line defect surrounded by defects of opposite sign, is approached by assuming that the transverse magnetization vanishes on a certain circle around the defect. For such a model one obtains a magnetic hardness term, when the radius of the circle is large compared to the fall-off distances of the disturbance in the material. For a radius much smaller than the fall-off distances, a parasitic paramagnetism term is obtained, with apparent reduction in the saturation magnetization value.
Initial Susceptibility of Ferromagnetic Iron and Iron-Vanadium Alloys just above Their Curie Temperatures
Authors: Noakes John E. , Arrott Anthony
Published: April 2005

Induction measurements of magnetization of spherical samples of Fe and Fe(V) alloys in low applied fields are used to deduce the temperature dependence of initial susceptibility near the critical temperature. The initial susceptibility follows an expression of the form χ=A(T−Tc)−γ, where Tc is the Curie temperature. The value of γ for Fe is 1.37±0.04. In dilute Fe(V) alloys γ decreases with increasing concentration of solute.
Magnetization of Gadolinium near Its Curie Temperature
Authors: Darnell F. J. , Cloud W. H.
Published: April 2005

Magnetization measurements on single crystals of gadolinium yield a Curie temperature of 290±1°K, determined by a plot of M2 vs H/M. Measurements of magnetization vs applied field extrapolated to zero field show appreciable magnetic order above this temperature. X-ray lattice parameter measurements on the same crystals allow estimation of magnetization in zero field and confirm the presence of magnetic order up to ∼305°. The zero field moment at 290°, M(T=290°)/M(T=0°), is estimated from lattice expansion to be 0.3, compared to a value of 0.2 obtained from the extrapolated magnetization measurements.
Exchange Inversion in Ternary Modifications of Iron Rhodium
Authors: Walter Paul H. L.
Published: April 2005

The effect of various transition metal modifiers on the magnetic properties of iron-rhodium alloys was studied. The exchange inversion temperature Ts, residual magnetization, and maximum magnetization are dependent on the nature of the modifier and on the degree of substitution. As little as 2 at. % of Co, Ni, Cu, Nb, Mo, Ta, or W eliminates the exchange inversion transition, while addition of Ru, Os, Ir, or Pt increases Ts over that for the comparable binary alloy, and addition of Pd, V, Mn, or Au decreases Ts. For the series of alloys FeRhIrx, Ts increases as x increases from 0−0.25; for the series FeRhPdx, Ts decreases as x increases. The range of composition over which exchange inversion is observed is quite narrow.
Flux Jumping in Nb +25% Zr Wire
Authors: Lubell M. S. , Mallick G. T. , Chandrasekhar B. S.
Published: April 2005

Flux jumping has been investigated in both cold-worked and heat-treated (1 h at 700°C) 0.025-cm-diam Nb+25% Zr wire wound into solenoids and noninductive coils of approximate dimensions: i.d.=0.3 cm, o.d.=1.2 cm, length=2.6 cm. The measurements taken at 4.2°K were: (1) The induced voltage pulses vs applied magnetic field with both I=0 and a preset transport current. (2) The induced voltage pulses vs coil current for H=0 and with a preset uniform external field.

For the case with no transport current in the coil (I=0) when the external field was increased smoothly from zero, a squence of very sharp voltage pulses (flux jumps) were induced in the coil, and recorded simultaneously on both an X-Y recorder and an oscilloscope. These flux jumps had the following general characteristics for all the cases discussed in this paper: (1) Starting from well defined initial conditions, the pulse always appeared at about the same place in the field sweeping cycle. (2) The polarity of the pulses is reversed when the direction of field change is reversed. (3) The pattern of these pulses was essentially unchanged when the field sweep rate was increased from 7 to 340 G/sec.

As a result of these measurements, we have obtained new insight into both the multilevel transitions of noninductive coils and the phenomenon known as degradation of solenoids. Two successful methods are described for partially overcoming the excessive degradation of a solenoid made from heat treated wire. The flux jumps are interpreted according to an extension of a model proposed by both Bean and London.
New Hexagonal Ferrite, Establishing a Second Structural Series
Authors: Kohn J. A. , Eckart D. W.
Published: April 2005

The hexagonal ferrites, of current interest because of their high-frequency properties, are being studied by single-crystal x-ray methods. A new rhombohedral member of the group, ideally Ba4Zn2Fe52O84, has been identified. The centrosymmetric space group is R3̄m; referred to hexagonal axes, c=153.85 Å, a=5.88 Å, and there are 66 anion layers in the c-axis repeat period. The stacking sequence was established by (00.l) structure factor and one-dimensional electron density calculations. The new structure forms a series of mixed-layer compounds with three of the original phases. All of the hexagonal ferrites are thus characterized by two series, each of which features the c-axis interlayering of two discrete structural units. Stacking relations within and between the two series are discussed, along with implications for new structures and series.
Ferromagnetic Europium Compounds
Authors: McGuire T. R. , Shafer M. W.
Published: April 2005

Ferromagnetism has been found in several divalent europium compounds. Some of these materials are particularly simple in both crystal and magnetic structure and are ideal for experimental and theoretical study. The materials we have investigated can be divided into three groups, europium chalcogenides, europium halogens, and europium silicates. Magnetic information on these compounds are summarized and theoretical results reviewed.

The europium chalcogenide series all have the rocksalt structure, the oxide, sulfide, and selenide being ferromagnetic, and it is on these materials that the most work has been done. This is especially true of EuS where detailed moment, specific heat, and nuclear magnetic resonance measurements are available. The oretical analysis indicates that there is positive exchange between nearest-neighbor europium atoms which decreases with increasing atom spacings. There is also a weaker negative superexchange via the anions in these compounds which is responsible for antiferromagnetism in EuTe. The EuTe magnetic ordering has been studied by neutron diffraction at Brookhaven and the sublattice magnetization-temperature behavior is found to be somewhat anomalous. EuSe is ferromagnetic but reveals low-field magnetization curves that have an unusual shape. In view of this, EuS seems to be the simplest of the group so that fundamental parameters obtained from analyzing the data are probably the most reliable.

In the halogen group, EuI2 appears to be ferromagnetic while EuF2 is apparently antiferromagnetic. The latter behavior is somewhat unexpected from interatomic distance considerations which hold for the chalcogenides. Of three silicates prepared, two were ferromagnetic. The most interesting was Eu2SiO4 which was obtained as transparent single crystals. Magneto-optical studies show this compound to have a Verdet constant higher than any other previously reported.
Temperature Effect on Langmuir Probe Measurement
Authors: Chen Che Jen
Published: April 2005

A substantial lowering of the work function of a tungsten Langmuir probe immersed in an argon plasma in a discharge tube is observed. The mechanism is thought to be similar to the Schottky effect. The electron temperature measurement is lowered about 30%, in a particular discharge condition, as the probe goes from room temperature to 2000°C. The charge number density measurement, by saturation electron current appears to be higher by 15%, and that by ion saturation current appears to be higher by almost one order of magnitude. This phenomenon can also account for the discrepancy of the ratio of ion and electron saturation current obtained by previous authors and this author.
Compression of Magnetic Field Between Two Semi-Infinite Slabs of Constant Conductivity
Authors: Paton Andrew , Millar William
Published: April 2005

A uniform magnetic field is compressed in a circuit containing two semi-infinite slabs of constant conductivity σ. The separation l of the slabs decreases uniformly according to l=l0−vt. An equation involving the magnetic Reynolds number Rm=σμ0l0v is derived for the magnetic field in the gap. Expressions are given for the magnetic and electric fields everywhere up to the instant of collision. These expressions are evaluated for several values of Rm and it is found that the ratio of Joule energy density to magnetic energy density at the surfaces of the slabs is fairly close to unity throughout the motion. For Rm»1 it is shown that the maximum magnification of the initial field is approximately Rm/8.
Effect of Crystallization Conditions and Heat Treatment on Polyethylene: Lamellar Thickness, Melting Temperature, and Density
Authors: Brown R. G. , Eby R. K.
Published: April 2005

Lamellar thickness, melting temperature, and density were measured for bulk polyethylene crystallized by the application of a fixed pressure to molten polymer at different temperatures. Melting temperature varied from 135.2° to 139.2°C, and density varied from 0.9759 to 0.9842 g/cc. Small-angle x-ray diffraction yields two maxima which apparently are not first and second orders of diffraction. Electron micrographs of fracture surfaces exhibit lamellae, which support the suggestion that the lamellar thickness is the shorter of the two dimensions (469≤L1≤981 Å and 193≤L2≤440 Å) corresponding to the diffraction maxima. However, the functional relationship of both dimensions to melting temperature and density are in accord with existing or easily derived equations. Analysis of these data, together with the result obtained from paraffin data, yields an equilibrium melting temperature of 141.9±1.7°C. Dimensions of the unit cell did not vary with lamellar thickness.

Single crystals of polyethylene were collected into mats and heated at a fixed temperature under various pressures. The observed effect of pressure was to limit the fold period attained during heat treatment. The data suggest that the refolding process follows a relationship which describes crystallization from the melt.
Determination of the Coefficient of Kinetic Friction in the Case of Extremely Small Displacements
Authors: Wild D. H. , Beezhold W. F.
Published: April 2005

This paper describes a simple technique for determining the coefficient of kinetic friction for extremely small displacements. An attempt was made to obtain more information about the transition stage between the coefficients of static and kinetic friction. If the force of static friction persists over small distances before falling to the lower value of the kinetic friction, such distances in the case of steel on steel are probably smaller than 5×10−6 cm. With the exception of very soft metals, higher values of the coefficient of static friction were obtained for impulsive forces than for slowly increasing tangential forces.
Spectrophotometric Determination of Chromium Concentration in Ruby
Authors: Dodd D. M. , Wood D. L. , Barns R. L.
Published: April 2005

A spectrophotometric method for determining the concentration of chromium in oriented and unoriented single ruby crystals is described. It makes use of the absorption coefficients for the blue and green bands and for the red lines at ∼300°K. The coefficients are based on concentration data obtained by three independent methods.
Variable-State Methods of Measuring the Thermal Properties of Solids
Authors: Harmathy T. Z.
Published: April 2005

Two variable-state methods have been developed which both offer the advantage of producing negligible thermal disturbance in a solid during measurement. The first is a curve-fitting method. It makes use of the fact that the initial temperature rise, due to a constant flux plane heat source, at points within a certain region of a finite solid is essentially the same as that in an infinite solid. Temperature records obtained from such points thus can be analyzed with the assumption of linear heat flow, and used for calculating all thermal properties of the solid.

The second is a pulse method. If a hot or cold pulse is applied to a plane surface of a specimen, the rise or drop of temperature at some distance from the surface will pass through a maximum; from the time of the maximum the thermal diffusivity can be calculated. The main advantage of this method is the ease of specimen preparation.
Dynamic Response of Aluminum
Authors: Barker L. M. , Lundergan C. D. , Herrmann Walter
Published: April 2005

The dynamic stress-strain relation of aluminum was measured in compression to a stress of 22 kbar using plate impacts to induce uniaxial strain. The results were compared to a uniaxial strain curve constructed from elastic moduli and quasistatically determined stress-strain curves. The dynamically determined stress-strain relation was not unique in that it varied as a function of the magnitude of the induced stress and was offset from the quasistatic curve. These small deviations are attributed to strain rate effects. The rate effects were further demonstrated by observing the transmission of an elastic compression stress wave in aluminum after the aluminum was dynamically stressed beyond the yield point and held at constant strain for a period of approximately 2 μsec.

The dynamic stress-strain relation was measured upon the release of a shock induced compressive stress of 10.5 kbar to a tension of −9 kbar by observing the effects of tensile stress waves. The deviation of the unloading stress-strain relation from that predicted by simple elastic-plastic theory is attributed to strain rate and Bauschinger effects.
Matteucci Effect: Its Interpretation and Its Use for the Study of Ferromagnetic Matter
Authors: Skórski Roman
Published: April 2005

A brief description of an Ampère electrodynamic experiment is given and some connection with it is indicated in such effects as those of: Wiedemann, Matteucci (MS), and Hall. Experimental arrangements and procedures in the MS study of ferromagnetics is described. The essential differences in the MS of different ferromagnetics are cited. An interpretation of the MS has been based on the well-known effect of the exchange energy in ferromagnetic metals dependent on the interatomic distances instead of a phenomenological interpretation in terms of the magnetostriction.
Elastic Constants of CsBr and CsI from 4.2°K to Room Temperature
Authors: Vallin J. , Beckman O. , Salama K.
Published: April 2005

The elastic constants of pure single crystals of CsBr and CsI have been measured at liquid-helium, liquid-nitrogen, and room temperatures. For CsBr, the values of c11, c12, and c44 at 4.2°K are 3.437, 1.035, and 0.999 in units of 1010 N/m2. The corresponding values of CsI at 4.2°K are 2.737, 0.793, and 0.825·1010 N/m2.

The elastic constants give the Debye temperature 148.8°K for CsBr and 125.6°K for CsI.

The infrared resonance frequencies calculated from compressibility data are in agreement with those obtained from infrared spectroscopy.
Refractive Index of GaAs
Authors: Marple D. T. F.
Published: April 2005

The refractive index of GaAs, as measured by the prism refraction method, is reported here for photon energies from 0.7 eV up to the absorption limit set by the band gap, for temperatures of 300°, 187°, and 103°K. The results are compared with the previous data (obtained only for room temperature), and are used to show that the spacing of emission lines of GaAs lasers corresponds to that of the axial modes of a Fabry-Perot resonator.
Radiation Hardening in Alkali-Halide Crystals
Authors: Nadeau John S.
Published: April 2005

Hardening by gamma irradiation was investigated in eleven alkali halides with the rocksalt structure. The linear dependence of the flow stress upon the one-half power of the F-center concentration, as previously observed in LiF and KCl, was also observed in these new substances. (The earlier experiments showed that the hardening is not actually caused by F cneters but by a defect resulting from F-center production.) The rate of hardening with concentration was found in all cases to be consistent with that to be expected for non-symmetrical defects. Comparisons were also made between the amount of hardening per defect and the lattice spaces available to certain specific defects. The only clear correlation was with a halogen atom in the interstitial space at coordinates 0, ¼, ¼ in the unit cell.
Governing Equations for the Shapes of Molten Zones
Authors: Green Robert E.
Published: April 2005

Theoretical consideration is given to the equation governing the shapes of molten zones when they are not necessarily surfaces of revolution. This equation is seen to reduce to equations previously given for both vertical and horizontal molten zones when the shape is a surface of revolution. Solution of the equation governing the shape of the vertical molten zone when it is a surface of revolution gives corrected values for the maximum stable zone lengths for large rod radii. Detail consideration is given to the influence of a surface film on vertical zone stability.
Maximum Average Energy Density as the Criterion for Phase Transition in Thin Superconductive Films
Authors: Cheng Kuang Liu
Published: April 2005

For recent experimental results on thin superconductive films, the maximum average energy density as a macroscopic criterion of superconductivity is in better agreement with observed behavior than are any of the earlier criteria—maximum magnetic field, maximum current density, or maximum energy density. The earlier criteria are briefly reviewed, and characteristic formulas and critical curves are applied to an example for comparison with the proposed criterion. To determine the full significance of the proposed criterion, further experimental and theoretical work is needed.
Vocabulary of Surface Crystallography
Authors: Wood Elizabeth A.
Published: April 2005

The recent increase of activity in the field of slow-electron diffraction has resulted in a need for agreement on conventions of terminology in the description of a diperiodic surface structure relative to a triperiodic substrate. Vector description of the surface structure net in terms of the substrate surface net is suggested. Fractional Miller indices result when the surface structure mesh is larger than the substrate surface mesh. The surface structure may be either that of a deposit or that of the selvedge of the substrate.

With the relaxation of one of the diffraction conditions in the diperiodic structure the reciprocal lattice becomes a set of parallel rods intersecting the Ewald sphere continuously with change of wavelength of the incident radiation or change of orientation of the crystal.

The paper discusses the applicability of the seventeen two-dimensional space groups and the eighty diperiodic groups in three dimensions to these diperiodic structures. A comparison is made between the different effects of surface symmetry on etch pits and epitaxial deposits on the cleavage face of muscovite.
Zinc Tungstate Crystal Growth, Dislocations, and Crystallography
Authors: O'Hara S.
Published: April 2005

Single crystals of zinc tungstate were grown by the Čzochralski method from melts prepared by various methods. Of the three chemical etches evaluated for purposes of revealing dislocations in this material, solutions of potassium or sodium hydroxides were most satisfactory. The (100) and (010) planes were shown to be slip planes. Both of these planes are parallel to the growth direction of crystals grown for maser applications. Annealing experiments indicated appreciable mobility of the dislocations at about 800°C. Etch pit counts revealed typical dislocation densities of 104−105 pits/cm2 in areas near the center, and around 106 pits/cm2 at outer regions of the crystal. Gaseous inclusions were frequently surrounded in their immediate vicinity by dislocations, and regions with a high density of these inclusions also had a high dislocation density. Some miscellaneous crystallographic information is also presented to enable crystals to be accurately orientated by simple optical methods.
Some Observations on the Interfacial Topographies of Aluminum and Its Amorphous Oxide
Authors: Randall John J. , Bernard Walter J.
Published: April 2005

The thin amorphous oxide formed in air on electropolished aluminum replicates the surface of the metal, resulting in identical topographies at the metal-oxide and oxide-oxygen interfaces. The observed configurations are attributed to surface features developed in the metal during electropolishing; these features vary widely depending upon electropolishing conditions. The formation of crystalline oxide at 600°C occurs at the metal-amorphous oxide interface even in the presence of thick amorphous layers formed by anodic oxidation. Evidence is given that cracks develop in the amorphous film on heating and that subsequent thermal oxidation proceeds through these defects.
Radiation-Induced Stress Relaxation in Quartz and Vitreous Silica
Authors: Primak W.
Published: April 2005

Helium or proton beams, penetrating several microns or more, cause crazing on vitreous silica surfaces. In a lower energy range (beams up to 150 keV were used) there was observed upon irradiation a plastic flow stress relaxation that relieved the stress from the radiation-induced dilatation and resulted in the total volume change in vitreous silica or quartz occurring perpendicular to the surface! Implications of this radiation-induced stress relaxation seem fundamental to the radiation behavior of quartz, silica, and similar substances, and are discussed.
Internal Resonances of a Discharge Column
Authors: Crawford F. W.
Published: April 2005

Dipole resonance of a cold plasma column can be predicted quite simply and observed experimentally. It is normally accompanied, however, by a series of subsidiary resonances. These have recently been explained phenomenologically as depending on nonuniform electron density and nonzero electron temperature for their existence. Numerical results of an analysis of the resonances by Nickel, Parker, and Gould are compared to the recently published experimental work on which the phenomenological description was founded, and it is shown that there is very good agreement. These observations and the theory have considerable relevance to the pressure waves described by Bohm and Gross, and to the effectiveness of Landau damping under conditions of nonuniform electron density. It is also possible to use the computed data to estimate the error in dipole resonance measurements of electron density.
Multimode Oscillations in Solid-State Masers
Authors: Statz H. , Tang C. L.
Published: April 2005

Previous work by the authors on the effects of slow spatial cross relaxation is extended in two directions. First, off-axis modes are included in the calculations, and thus it becomes possible to calculate the number of oscillating off-axis modes as a function of the various laser parameters. In this way the expected beam angle of a laser can be predicted. Second, a more detailed analysis of the spiking behavior is given; both regular and irregular spiking trains may be obtained depending upon the laser parameters and the pump power.
Optical Constants in the X-Ray Range
Authors: Philipp H. R. , Ehrenreich H.
Published: April 2005

In conjunction with x-ray transmission data, the integral relationship between the refraction index and the absorption coefficient can be employed to extend the range over which optical constants have been determined by Kramers-Kronig analysis of reflectance data. The procedure is applied to measurements on aluminum and the optical constants are determined for the energy range 10−3 to 105 eV. The results are useful in testing some general sum rules. They also permit a comparison of the behavior of the dielectric constant for energies above the K absorption edge with the expected asymptotic behavior.
Dielectric Breakdown of Single-Crystal Strontium Titanate
Authors: Barrett Harrison H.
Published: April 2005

Measurements of the intrinsic dielectric breakdown strength of single-crystal strontium titanate over a temperature range from −195° to +100°C and under both pulse and dc conditions are described; dc breakdown at +100°C is thermal in origin. At room temperature and at −40°C the breakdown strength is independent of duration of applied field and of sample configuration and hence may properly be termed intrinsic. At −80° and −195°C, both the values of breakdown strength and the scatter of the data depend strongly on sample configuration. The breakdown strength unexpectedly decreases with increasing temperature. Current-voltage curves show an anomalous saturation effect at low temperature. These effects may be qualitatively explained by postulating that the high electrostrictive stress causes the creation of electron trapping centers.
Measured Temperatures of Strong Shock Waves in Argon
Authors: Roth J.
Published: April 2005

Plane shocks generated in atmospheric pressure argon by detonating Comp B-3 have been viewed with a photomultiplier-interference filter system. Visible radiation from these Mach 27 shocks was that from a blackbody at a color temperature of 29 000°±1000°K, about 20% higher than calculated. The risetime to peak intensity is interpreted in terms of increasing opacity, and consequently of emissivity, as the shocked zone increases in thickness. Photon absorption coefficients based on this interpretation are in reasonable accord with those calculated from a modified Kramers's formula.
Application of Thermodynamics to Thermomechanical, Fracture, and Birefringent Phenomena in Viscoelastic Media
Authors: Schapery R. A.
Published: April 2005

A unified theory of the thermomechanical behavior of viscoelastic media is developed from studying the thermodynamics of irreversible processes, and includes discussions of the general equations of motion, crack propagation, and birefringence. The equations of motion in terms of generalized coordinates and forces are derived for systems in the neighborhood of a stable equilibrium state. They represent a modification of Biot's theory in that they contain explicit temperature dependence, and a thermodynamically consistent inclusion of the time-temperature superposition principle for treating media with temperature-dependent viscosity coefficients. The stress-strain-temperature and energy equations for small deformation behavior follow immediately from the general equations and, along with equilibrium and strain-displacement relations, they form a complete set for the description of the thermomechanical behavior of media with temperature-dependent viscosity. The role of thermodynamics in finite deformation and crack propagation problems is examined. Restrictions placed on the constitutive equations by thermodynamics is illustrated by considering a familiar stress-strain equation for polymers, wherein the time and strain dependence of stress in a relaxation test appear as separate factors. In addition, an energy equation for crack propagation is derived and then applied to a specific problem. Thermodynamic implications concerning birefringence are also discussed and an operational stress-optical coefficient is derived.
Ultrasonic Attenuation and Velocity in Three Transformation Products in Steel
Authors: Papadakis Emmanuel P.
Published: April 2005

Ultrasonic attenuation measurements were made from 2 to 100 Mc/sec in the pearlitic-plus-ferritic, bainitic, and martensitic transformation products in SAE 4150 steel, a low-alloy, 0.5% carbon variety. Measurements were also made in the martensitic specimen after tempering. Ultrasonic velocity measurements were made at 10 Mc/sec in each case. To eliminate the question of grain size and grain size distribution, three specimens were treated identically through the austenitizing operation. Then they were cooled differently to produce the three transformation products. The attenuation can be expressed as Af4+Cf2, where f is frequency. The first term is Rayleigh scattering and the second may be from dislocation damping, atomic relaxations, or magnetic domain boundary effects. Both A and C are strong functions of microstructure. Both coefficients decrease in the order pearlite-plus-ferrite, bainite, martensite, tempered martensite. On tempering, A decreased in the ratio 3:2 while C decreased 3:1. In pearlite-plus-ferrite, A is larger by a factor of 225 than it is in tempered martensite, and C is larger by a factor of 10. The ratio CT/CL (T = transverse waves, L=longitudinal waves) was a constant independent of microstructure and equal to 2.4. This suggests either dislocation damping, an atomic relaxation, or a magnetic effect. The large change in C on tempering (with CT/CL = constant) indicates that the interstitial carbon is involved. The ultrasonic velocity measurements showed an increase in velocity on tempering the martensite. Pearlite-plus-ferrite has the highest velocities and density, while raw martensite has the lowest. The differences in velocities arise primarily from differences in the elastic moduli of the transformation products, not from the density differences.
Ultrasonic Attenuation in Cadmium Sulphide above Room Temperature
Authors: Truell Rohn , Elbaum Charles , Granato Andrew
Published: April 2005

The temperature dependence of the attenuation of 30-Mc/sec longitudinal ultrasonic waves has been measured from room temperature to 380°C in CdS. The observed attenuation is in good agreement with the theory of Hutson and White and with the temperature dependence of the resistance measured on the same specimen.
Optical and Electrical Properties of Selenium-Tellurium Alloys
Authors: Lanyon H. P. D.
Published: April 2005

The optical and electrical properties of selenium-tellurium alloys have been studied. These properties depend upon the degree of order of the alloys. The bandgap of disordered evaporated layers of the alloys Se3Te and SeTe have been estimated to be 1.87 and 1.58 eV, respectively, from the break from the approximately exponential absorption edge. This is consistent with a linear variation of bandgap with composition. From the dispersion of the refractive index, another characteristic frequency larger than the bandgap is found. The disordered layers convert to a crystalline form when heated above room temperature. The conversion process has been followed by observing the change of resistivity of the layers with time. During much of the conversion, this change is approximately exponential. The time constant in this region has an exponential temperature dependence, being characterized by activation energies of 1.4 and 0.8 eV for Se3Te and SeTe, respectively. The rate of conversion of the alloys increases with increasing tellurium content. As with selenium, the ordered alloys are more conducting than the disordered alloys and the absorption in the low photon energy region is greater. An absorption band has been found in the ordered alloys which is associated with transitions between tellurium levels. The strength of the band is directly proportional to the tellurium concentration; the energy of separation of the levels, which is a reflection of the local crystal field, varies linearly with the composition of the alloys.
Some Observations on Conduction through Thin Tantalum Oxide Films
Authors: Standley C. L. , Maissel L. I.
Published: April 2005

The electrical properties of several tantalum oxide diodes with various metal counterelectrodes have been studied. The devices were prepared on sputtered tantalum by anodizing to the desired oxide thickness (100–200 Å) and evaporating the second metal electrode in vacuum. The devices show a work function dependence on the second metal electrode that also appears to be affected by the manner in which the original tantalum was prepared. The temperature behavior of this and several other oxide diode systems follow a Schottky relation fairly well, with deviations at low temperatures and thinner oxide layers, as expected.
Properties of Rare-Earth Nitrides
Authors: Sclar N.
Published: April 2005

The optical and electrical properties of the rare-earth nitrides DyN, ErN, and HoN as well as ScN and YN have been surveyed. From absorption edges found in the optical transmission curves, energy gaps in the 2-eV range were determined as follows: DyN 2.60–2.90 eV, ErN 2.40–2.78 eV, HoN 1.70–1.88 eV, where the spread in energies is due to differences observed in two experimental runs. For ScN and YN no definite absorption edge was found. The electrical properties from 80° up to 1500°K were found to be metallic with associated large concentrations of electron carriers. These results are interpreted to suggest that the present species of nitrides which were all deficient in nitrogen content are high energy gap defect type degenerate semiconductors. The large concentrations of charge carriers are attributed to the lack of stoichiometry so far achieved.
Components of the Two-Band Resistivity Tensor in Semiconductors
Authors: Moore R. G. , Stamper John A.
Published: April 2005

The components of the two-band resistivity tensor are determined as functions of the two single-band carrier concentrations and mobilities to yield the general equations for the two-band resistivity and Hall coefficient. The conductivities which usually appear in the two-band formulas for Hall coefficient and ``conductivity'' are reciprocals of the components of the resistivity tensors and are not components of the conductivity tensor. The two-band equations reduce to those of Kurnick and Zitter for semiconductors by assuming (1) that a time of relaxation for the carriers exists and that it is energy independent or (2) that the magnetic field is sufficiently large.
Vapor-Deposited, Thin-Film Heterojunction Diodes
Authors: Muller R. S. , Zuleeg R.
Published: April 2005

Deposited heterojunctions between semi-insulating CdS thin films and insulating materials have been fabricated, and their characteristics studied. Excellent rectification properties are obtained in which contact-field emission from the heterojunction carries the forward currents. Field emission of this type exhibits several characteristics which differ from the Schottky field emission. These differences stem from the nondegeneracy of the electron source in the heterojunction case. Correspondence between the theoretical predictions for the behavior of such emission, as derived in this paper, with observed temperature and voltage dependence is very good. The theory developed may account for the low value for the Richardson factor obtained experimentally for oxide-coated vacuum emitters. The structures studied consist of Al contacting a film of deposited CdS roughly 1 μ in thickness. Three different insulating materials CdTe, Al2O3, and SiOx were used to form the thin insulating film between the CdS and the metallic counter electrode.
From Micrograph to Grain-Size Distribution with Ultrasonic Applications
Authors: Papadakis Emmanuel P.
Published: April 2005

A matrix inversion procedure is presented for the computation of the grain-size distribution NV of a solid volume from the image-size distribution on a photomicrograph of its surface. Averages over the distribution NV are taken to find the average volume to use in ultrasonic scattering formulas. For several metals, NV is adequately expressed in terms of the grain radius R as NV=A (R−R0) exp (−aR) where R0, A, and a are constants for a specimen. NV is zero for R<R0. Relationships are developed between the average volume and the sizes of the images on a photomicrograph, as well as between the average radius Rav of the grains and the average radius rav of the images. The results of ultrasonic attenuation experiments agree well with theoretical predictions when the average scattering volume is computed from the grain-size distribution. Agreement is especially good when the metal grains are single crystals. The martensitic transformation lowers the experimental attenuation by a factor of about 10; the process is thought to be a lowering of the anisotropy of the grain through averaging over all the platelets. Pearlitic steel, on the other hand, has higher attenuation than theory predicts. The grain-size distribution will be useful in other problems involving average sizes of grains.
Floating-Zone BaTiO3: Preparation and Properties
Authors: Brown F. , Todt W. H.
Published: April 2005

Single-crystal boules, 2.5 cm long by 0.32 cm diameter, of ferroelectric BaTiO3 containing 1.5% SrTiO3 have been grown by a floating-zone process. Since the use of a crucible to contain the molten material is avoided high inherent purity is achieved. In addition boule shape permits studies not feasible with the earlier butterfly wing crystals of Remeika. Several of the ferroelectric and structural properties have been measured and are similar to those well known for crystals grown by other methods. X-ray rocking curves possessing double peaks have been observed, an effect which is ascribed to ferroelectric domains.