bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cycloidal Spin Configuration of Orthorhombic MnSO4
Authors: Will G. , Frazer B. C. , Shirane G. , Cox D. E. , Brown P. J. 
Published: April 2005

The crystal and magnetic structures of antiferromagnetic MnSO4 (a=5.260 Å, b=8.042 Å, c=6.847 Å, space group Cmcm) have been determined from x-ray and neutron diffraction data collected from polycrystalline samples at 300° and at 77° and 4.2°K, respectively. The neutron diffraction pattern at 4°K exhibits additional peaks of magnetic origin which are slightly displaced from the positions expected on the basis of the original unit cell, or any simple multiple cell. In addition, the observed extinction rules cannot be satisfied by any combination of simple collinear magnetic structures. Complete indexing of the magnetic peaks can be achieved only on the basis of a cone spiral arrangement related to a simple antiferromagnetic structure of CrVO4 type,1 in which ferromagnetic (001) sheets are coupled antiparallel to adjacent sheets. The propagation vector of the spiral is along the a axis with a periodicity of 30 Å (almost 6a). The spin plane of the spiral component is the a-b plane. It is believed that this is the first case in which a spiral has been observed in an orthorhombic compound, and it is of particular interest that the spiral is cycloidal.
Good agreement of observed and calculated magnetic intensities is obtained with a fundamental spin component of 1.7 μB directed along the c axis, and a spiral component of 4.5 μB in the a-b plane. The resultant moment of each Mn2+ ion is therefore 4.8 μB, and the cone half-angle is about 78°. The temperature dependence of the satellite peaks indicates a Néel point of about 10°K.
Investigation of Eddy-Current-Induced Nondestructive Readout in Thin-Film Memories
Authors: Maltz M. S. 
Published: April 2005

When a magnetic thin-film bit is switched, eddy currents arise, creating fields which tend to remagnetize the bit in its original direction. A structure in which these fields are strong enough to produce NDRO was given a preliminary investigation. The bits were nickel-iron 17–83 Permalloy, 50×50 mil by 500 Å, evaporated onto a glass substrate. The structure layers were: bit line, word line, planar sense line, bit, glass, and word line. If the word drive pulse was 100 nsec long or less, the structure with the most unfavorable geometry gave stable NDRO at drive currents up to 10 times as large as the normal DRO value. Scale factors are displayed and applied to show that NDRO is possible with structures much smaller than the one tested. The eddy fields could even remagnetize partially demagnetized bits.
When the eddy field was measured as a function of time and geometry, the time constant and magnitude of the decay was a sensitive function of the word linewidth and separation, varying between 76 and 191 nsec. Experimental and theoretical evidence was found for a rapid transient decay mode which precedes the slower decay mode observed in the experiments.
Band Structure of Gadolinium Metal
Authors: Dimmock J. O. , Freeman A. J. , Watson R. E. 
Published: April 2005

The heavy rare-earth metals have been viewed traditionally as consisting of trivalent atomic cores plus three conduction electrons per atom. Previous theoretical work1-3 has attempted to explain the available experimental data by assuming that the three conduction electrons occupy essentially free electron-like bands. We have obtained approximate nonrelativistic energy bands for Gd metal using the augmented plane wave method.4 The calculated bands differ markedly from the free electron model due to the fact that the bands originating from atomic 5d and 6s states overlap and are strongly mixed. The bands, in fact, show a close resemblance to those of the transition metals. This resemblance also appears in the calculated density-of-states curve. The density of states at the Fermi energy is large, about three times that of the free electron model. This density of states is about one half that given for Sc, Y, and La by specific heat measurements.
A detailed version of this paper will be submitted to the Physical Review.5
The Constitution of CuFe5O8
Authors: Jefferson C. F. 
Published: April 2005

The physical properties of the system CuFe2O4–Fe3O4 point to the existence of the compound CuFe5O8. The activation energies Ea of quenched specimens exhibit an anomaly at the composition CuFe5O8. The log of the resistivities plotted as a function of composition changes slope, the Curie temperatures Tc display a minimum, and the lattice constants A0 show a maximum at or near this composition.
As the iron concentration increases, the Seebeck coefficients θ change from positive to negative at the composition Cu0.55(CuFe)0.225Fe2O4. This is interpreted as being due to the introduction of some ferrous iron at this composition. The equilibrium Cu+1+Fe+3↔Cu+2+Fe+2 lies to the left at least up to this composition. Since the changes in ρ, Ea, A0, and Tc occur at or near the composition CuFe5O8, it is concluded that only a little ferrous iron exists even in the region of n-type conductivity, and that the copper within parentheses is predominantly monovalent in the series Cu1−2x+2(Cu+1Fe+3)xFe2O4.
Flux-Jumping Behavior of Some Niobium-Tin Solenoids
Authors: Rosner C. H. 
Published: April 2005

Oscillographic and X-Y recorder observations have been made of the flux-jumping pattern in several superconducting Nb3Sn solenoids at magnetic fields ranging from 15 to above 100 kG at 4.2°K. It is noted that flux jumping is much more frequent in these solenoids than is observed in Nb–Zr solenoids. The flux-jump pattern extends throughout the high-field region. It can be modified, however, by gross rate changes in current increase, as well as by application and removal of external fields which change the induced magnetization.
Frequent quenching of the Nb3Sn superconducting solenoids does not seem to alter the flux-jump behavior appreciably. The relationship of a superconductive transition to flux jumps occurring just prior to the transition is discussed.
It is suggested that the more frequent but often lower-amplitude flux jumps in these niobium-tin solenoids contribute to the smaller coil degradation effect noticed as compared to niobium-zirconium solenoids. To eliminate, or at least minimize this effect, further exploration of magnetic instabilities and influence of material parameters is required.
Electronically Variable Delay of Microwave Pulses in Single-Crystal YIG Rods
Authors: Kaufman I. , Robinson W. A. 
Published: April 2005

Experiments on electronically variable time delay of microwave pulses by transmission through single-crystal YIG rods are discussed. One type of delay, recently discussed by Olson and Buchmiller and by Kaufman and Soohoo and attributed to magnetostatic waves, occurs with unpolished ends, has rapidly increasing delay with increasing Hdc, and has severe pulse dispersion. The second, found here, requires parallel and polished ends, has a slowly decreasing delay with increasing Hdc, and usually has at least two pulses spaced by less than the round-trip time through the rod. Characteristics are similar to those described by Strauss, except that his experiments were of pulse reflection.
The two aspects of magnetostatic wave pulse delay to be discussed are: (1) Additional experimental verification of Schlömann's theory of wave excitation by nonuniform demagnetizing fields, by grinding a rod into ellipsoidal shape, and by measure coupling. (2) A nonreciprocal microwave time delay has been constructed utilizing magnetostatic waves in a YIG rod to couple two rectangular waveguides. The coupling is between the positions in the waveguide where the magnetic field is circularly polarized. The directionality of the coupling was found to be greater than 15 dB with delays of 4 μsec at 2500 Mc/sec.
X-Ray Yield and Line/Background Ratios for Electron Excitation
Authors: Birks L. S. , Seebold R. E. , Grant B. K. , Grosso J. S. 
Published: April 2005

X-ray yield in photons/sr/electron was measured for the Kα lines of Ti, Cr, Mn, Fe, Cu, Zn, Ge, Zr, and the Lα lines of Ta and Au. Incident electron energy was varied from 11 to 38 keV, and for some elements the take-off angle for emerging x rays was varied from 6 to 45 deg. Theoretical yield values calculated after the method of Metchnik and Tomlin showed an average deviation of about 30% from the measured values, a very satisfactory agreement.
Line/background ratios were also measured for the same elements and conditions. Normalization to the natural x-ray line breadths gave ratios between 100/1 and 26 000/1 depending on the element and experimental conditions. Line/background ratios are consistently larger at low take-off angles indicating that the characteristic radiation must be generated relatively closer to the surface than the continuum of the same wavelength.
Twist and Axial Imperfections in Filamentary Crystals of Aluminum Nitride. II
Authors: Drum C. M. 
Published: April 2005

Simultaneous and independent measurements have been made of the magnitude and direction of the lattice twist and of the direction of the Burgers vector of the axial dislocations in filamentary crystals of AlN, using electron microscopy and electron diffraction. The twist was revealed by extinction contours from reflecting planes with normals perpendicular to the filament axis, and measurements of the widths and separations of these contours were used to calculate the twist.
Good agreement with theory was found in the case of crystals containing the simple axial dislocation, but crystals with a complicated extended axial imperfection were found not to be twisted. It is believed that the extended axial imperfection was a fault which met the surface of the crystal and which originated from an axial dislocation; the lack of twist was then due to one or more partial dislocations having left the crystal.
Nonlinear Shielding in Rare-Earth Crystal Field Interactions
Authors: Freeman A. J. , Watson R. E. 
Published: April 2005

A number of the magnetic properties of rare-earth ions, which depend strongly on their interaction with the crystalline environment, are inferred by studying their electronic spectra. Basic to current methods for analyzing these spectra is the assumption of a static crystalline field Vc which acts on the open 4f shell. Generally, one takes Vc=Σn,mAnmrnn Ynm(θ, φ). In fitting observed spectra, matrix elements of Vc over the 4f electrons alone are considered and one is left with the quantities Vnm=Anm 〈rn〉 (where 〈rn〉 is the integral of rn over the 4f radial density) which are taken to be empirical parameters which somehow absorb all environmental effects not included in Vc. These empirical parameters have been used ``successfully'' to interpret other rare-earth properties. However, if one considers multi-electron Coulomb and exchange contributions arising from the closed shells, it may be shown1 that, in addition to the occurrence of substantial linear shielding effects1,2 (which reduce the magnitude of the Vnm parameters), there may be significant nonlinear shielding contributions which change the ordering and spacing of the electronic energy levels. When these latter terms are significant, the standard parameterization scheme breaks down.
Previous work1 on Ce3+, using perturbation theory techniques, was seen to be inadequate for accurate estimates of nonlinear shielding. We have extended these investigations using configuration interaction methods to estimate the leading nonlinear (and linear) shielding terms in a number of ions, Ce3+, Tb3+, Er3+, Tm3+, Ho3+, Dy3+, and Yb3+. Calculations have been carried out as a function of crystalline field strength since the nonlinear shielding is dependent, of course, on the strength of the applied external field. Nonlinear shielding of V2 and V4 external fields were determined as a function of atomic number as were their effects on apparent V2, V4, and V6 crystal field parameters. From these certain conclusions may be drawn. Antishielding rather than shielding of the V4 field occurs, but only by a few percent at most, whereas the V2 field is always shielded. For the heavy rare-earth ions, the shielding effects are much smaller than for the lighter ions, with the apparent V4 and V6 shielding being very small. The most severe nonlinear effects arise when relatively strong V2 and V4 fields contribute to a relatively weak V6 field.
A full report will be submitted to the Physical Review.
Investigation of the Effect of O2, N2, and H2O on Nickel Thin Films
Authors: Freedman J. F. 
Published: April 2005

The role of oxygen, nitrogen, and water vapor adsorbed during the evaporation process was investigated for nickel films grown on room-temperature glass substrates. A change in pressure from 10−10 to 10−7 Torr oxygen caused a marked shift in the resonance field and the perpendicular anisotropy (i.e., the anisotropy resulting from the rotation of the magnetization out of the plane of the film). This shift could be accounted for by an increase in internal stress from 5×109 dyn/cm2 at 10−10 Torr to 2×1010 dyn/cm2 at 10−7 Torr. The wall-motion coercive force also increased with increasing pressure, ranging from 50 to greater than 200 Oe. Samples made in pressures as high as 1×10−5 Torr nitrogen appeared identical (as determined by the measurements) to films made in residual vacuum of 10−10 Torr. The presence of water vapor caused a slight increase in internal stress and Hc when the pressure changed from 10−10 to 10−5 Torr. The effect appears to be related to an internal oxidation phenomenon.
These experiments clearly demonstrate the role of impurity atoms in determining the stress-sensitive magnetic properties of films and emphasises the need for controlling the partial pressures of gases during evaporation, and not just the total pressures.
Metal-Semiconductor Barrier Height Measurement by the Differential Capacitance Method without an Ohmic Reference Contact—One-Carrier System
Authors: Goodman Alvin M. 
Published: April 2005

In previous treatments of metal-semiconductor contact barrier height measurements by the differential capacitance method it has been generally assumed that there exists an Ohmic reference contact to the semiconductor. In this paper, the method is extended to those cases where an Ohmic contact to the semiconductor is not available. It is shown that under certain conditions, barrier heights may be determined using only barrier reference contacts. It is also shown that although only two contacts are necessary, a third contact may be advantageously employed to simplify the measurement technique. If four contacts are available, a further simplification may be achieved.
Experimental results on Au–CdS contacts are used to verify the theory for the case of two symmetrical barrier contacts.
Orientation Overgrowth of Condensed Polycyclic Aromatic Compounds Vacuum-Evaporated onto Cleaved Face of Mica
Authors: Uyeda Natsu , Ashida Michio , Suito Eiji 
Published: April 2005

When Pt-, Cu-, and Zn-phthalocyanines are vacuum-evaporated onto cleavage faces of muscovite, single-directional orientation occurs at lower substrate temperature. At higher temperature ranges, Zn-phthalocyanine has a double-directional orientation while Pt- and Cu-phthalocyanines show triple-directional ones. High-resolution electron diffraction patterns, which were well-defined fiber diagrams, revealed that all three compounds showed conspicuous isomorphism with one another, and Zn- and Cu-phthalocyanines occurred in the metastable forms of their dimorphs. General crystal structures of metastable forms are discussed on the basis of the found isomorphism with Pt-derivative.
Evaporated films were composed of lamellar crystal strips, and the fiber diagrams showed that at least two kinds of lattice orientations were assumed by all three compounds, while the longitudinal crystal axis of individual strips always ran parallel to their b axes.
As to relative orientation of the evaporated films to the substrate, the b axis of the former was parallel to either of the two directions which made ±60° with the a axis of muscovite in the case of the single-directional orientation. When the evaporated films had double- or triple-directional orientations, the electron diffraction pattern showed twofold symmetries in spite of the apparent triangular configuration. It turned out that this axis of twofold symmetry also coincides with the same axis of muscovite as above. It is presumed that the unique orientation axis of the evaporated films coincides with the staggering direction of the two oxygen tetrahedron sheets in the top subcell of muscovite. Plausible origin of these orientations are also discussed in terms of lattice vibration near the surface.
Lattice imperfections of the evaporated films were directly observed in the lattice image obtained by the high-resolution electron microscopy. The dislocation density seems rather high when compared with other similar lamellar crystal strips of the same compounds formed by colloid chemical methods. This was ascribed to the crystal formation controlled by the epitaxial effect.
Complex Potential Analysis of Screw Dislocation Arrays
Authors: Webster L. D. , Johnson H. H. 
Published: April 2005

Complex potential theory is utilized to analyze the mechanics of screw dislocations on arbitrary glide planes. An analogy with airfoil theory is shown to be useful. General procedures are given for calculating stress fields and distribution functions with the aid of conformal mapping.
The theory is applied to several specific problems, including dislocations on a circular glide plane, on perpendicular intersecting glide planes, and on a glide plane within a thin film. Applications to dislocation pile-ups on neighboring glide planes are also given.
Thermal Conductivity of Sulfur Accompanying Crystal Transition and Phase Change
Authors: Sugawara Akira 
Published: April 2005

The thermal conductivities of both the solid sulfur and the liquid sulfur were continuously measured with an accuracy of ±1.0%. The temperature range in this experiment is from 0° to 160°C. In the temperature range from 0° to 160°C, two transition points exist; one of them is the transition point from rhombic sulfur to monoclinic sulfur at 95.5°C, and the other is the change point from monoclinic sulfur to liquid sulfur at 118.9°C. At each transition point, discontinuous and conspicuous changes in thermal conductivities can be observed by this experiment.
Moreover, a new result was obtained: The thermal conductivity of monoclinic sulfur decreases with increasing temperature, although the conductivity which was obtained by Kaye's experiment increases with temperature increment.
Effect of Stress on the Superconducting Transition Temperature of Thin Films of Tin
Authors: Hall P. M. 
Published: April 2005

Factors which affect the superconducting transition temperature (Tc) of thin tin films are of considerable importance in the design of thin film devices. This paper reports an investigation of one such factor, the stress state of the film. Two approaches were used. First, the transition temperature was correlated with the differential thermal contraction between film and substrate. Six different types of glass were used for substrates, and the six films were evaporated simultaneously to ensure similar conditions of evaporation. Secondly, a substrate-bending technique was used to stress the film while holding it near its transition temperature. For both of these methods, shifts of the transition temperature greater than 0.1°K have been observed. However, it was found that agglomeration of the film can greatly reduce the dependence of the transition temperature on stresses transmitted to the film by the substrate.
When agglomeration was negligible, both these approaches yielded a linear increase in Tc with tensile strain. Values for d lnTc/d lnv were obtained, where v is the volume of the tin film. The average values were +8.6 from the differential thermal contraction measurements, and +8.1 from the substrate bending measurements. These results are in reasonable agreement with the properties of bulk tin (d lnTc/d lnv=+7.5). However, the films were able to withstand tensile stresses more than an order of magnitude greater than the elastic limit of bulk tin and still recover their original properties upon relaxation.
Time-Dependent Computer Analysis of Electron—Wave Interaction in Crossed Fields
Authors: Yu S. P. , Kooyers G. P. , Buneman O. 
Published: April 2005

A time-dependent analysis of crossed-field interaction has been formulated for computer calculation. The computer program has achieved, for the first time, accurate and complete simulation of the magnetron oscillator, magnetron amplifier, and smooth-bore magnetron. We believe that crossed-field interaction of the distributed-emission type is finally predictable. The computer results are reliable enough to serve as design information. They also indicate that the nature of the interaction is turbulent in the sense that the operation of these devices borders between order and disorder under certain conditions.
The techniques used in this analysis are applicable to a wide range of problems dealing with other types of electron—wave interaction, and to plasmas.
Interaction of Diffusion and Stacking Faults in Si Epitaxial Material
Authors: Jaccodine R. J. 
Published: April 2005

The effect of diffusions and heat treatments on faulted epitaxial materials has been investigated using thinned-film electron microscopy. Samples of epitaxial silicon were grown with a deliberately high concentration of stacking faults for these studies. Heat treatment were performed in N2 and He ambient at 1000°, 1100°, 1200°, and 1300°C. Diffusion consisted of a 1050°C heat treatment for 30 min in P2O5 (platinum box technique) to give a high concentration layer (&gt; 1020/cm3). Heat treatments alone had a minor effect on the faulted material. The diffusion process, on the other hand, caused major alteration in the nature and density of faults. Stacking faults were altered to the extent that the orderly striped contrast disappeared and was replaced by individual or piled-up groups of dislocations. Large clusters of precipitate were observed inside stacking fault regions and on helical dislocations. Dislocation climb was detected as indicated by a large number of helical dislocations.
The presence of a ``necklace of precipitate'' associated with stacking faults and dislocations illustrates the role played by these faults as nucleation sites. Such precipitation occurring in an active device region might well be sufficient to drastically alter or destroy the device.