bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic Band Structure, Fermi Surface, and Magnetic Properties of Palladium Metal
Authors: Freeman A. J. , Furdyna A. M. , Dimmock J. O. 
Published: April 2005

The electronic energy bands of Pd metal have been determined using the nonrelativistic A.P.W. method. The Fermi surface, which consists of two hole surfaces and a compensating electron surface, agrees very well with the de Haas-van Alphen data of Vuillemin and Priestly. The electron surface is centered at Γ and contains approximately 0.3 electrons per Pd atom. One hole surface consists of a small pocket centered at X. The other hole surface is open along the [100] directions in agreement with galvanomagnetic measurements. The Fermi energy lies slightly above a maximum in the calculated density of states N (E) as expected from studies of dilute alloys. Using the computed N (EF) we obtain an electronic contribution to the specific heat which is only about half the observed value, indicating an electron-phonon enhancement typical for d-band metals. The computed paramagnetic susceptibility χ(T) is much smaller than the experimental value, emphasizing the importance of exchange in markedly enhancing χ(T), particularly at low temperatures.
A full account of this work will be submitted to the Physical Review.
Changes in Apparent Symmetry with Magnetic Field in Chromium
Authors: Werner S. A. , Arrott A. , Kendrick H. 
Published: April 2005

The magnetic states of chromium are described in terms of fundamental wave vectors Q1, Q2, and Q3 and the polarizations associated with these Q vectors. If the magnetic reflections in neutron-diffraction experiments show Q1, Q2, and Q3 all present and contributing equally to the single-crystal diffraction pattern, we speak of the ``apparently cubic'' state. If only one Q vector is present, we speak of a ``single Q'' state. Cooling through the first-order paramagnetic-antiferromagnetic transformation at 38.5°C produces an ``apparently cubic'' state if no field is applied during cooling while the application of a field of 40 kG can produce a ``single Q'' state in some crystals. In other crystals 40 kG is not sufficient to produce an entirely ``single Q'' state. The preferred Q is parallel to the applied field; the polarization is then perpendicular to the field. If the field applied during cooling is less than necessary to completely suppress Q1 and Q3 while enhancing the contributions from Q2, the polarizations of Q1 and Q3 prefer the field direction. In the low-temperature phase of chromium, where the polarizations are parallel to the Q's, the application of 160 kG is sufficient to change an ``apparently cubic'' crystal into a state with one Q missing. The ``missing Q'' is parallel to the direction of the field.
The critical scattering at 40°C shows that all three wave vectors Q1, Q2, and Q3 are equally represented in the wave-vector-dependent susceptibility and that the longitudinally polarized fluctuations are comparable to the transversely polarized fluctuations. The tetragonality of the Fermi surface of the ``single-Q'' state does not cause a large enough lattice distortion to be detected with an x-ray technique sensitive to 1 part in 2×104.
Composite Films as a Domain-Wall Barrier
Authors: Hunt R. P. , Jaecklin A. A. 
Published: April 2005

The use of multilayer magnetic films to constrain domain walls to localized regions is discussed. In particular, films which consist of a composite of hard and soft films are investigated; the soft film is continuous, whereas a window is provided in the hard film.
It is demonstrated that the edge of a hard film (Hchard≃20 Oe) provides an effective barrier for domains propagating in a window of soft Permalloy film (Hcsoft≃2 Oe). This is an alternative technique which offers a number of advantages over tapered edges, alloy compositional variations substrate roughening, and masked evaporation. Specifically, electrodeposition combined with photographic masking facilitates fabrication.
An expression for the effective ``punch-through'' field required to drive a domain wall into the composite film is derived. It is concluded that the ``punch-through'' field Hpt is approximately given by Hpt≃(Hncomp+2Hcsoft)/3,where Hncomp is the nucleation field of the composite film and Hcsoft is the coercive force of the soft film. Measurements on the ``punch-through'' fields from magneto-optic and Bitter pattern observations are presented.
Magnetization of Holmium Iron Garnet at 4.2°K
Authors: Allain Y. , Bichara M. , Herpin A. 
Published: April 2005

Magnetic measurements have been made on a spherical single crystal of holmium iron garnet at 4.2°K, in fields of up to 44 kOe. The sample was mounted in such a way that, by rotation about a 〈110〉 direction, any direction lying in the plane perpendicular to the axis of rotation could be brought parallel to the applied field and held there. An extraction method was used for these measurements.
In any direction, domain movement is observable only below 6 kOe; above this the magnetization varies linearly: M (H) = M (0)+χH. M (0) has a flat maximum about the direction of easy magnetization 〈111〉. The directions 〈110〉 and 〈100〉 are directions of difficult magnetization where M (0) exhibits very sharp minima. We find that M (0) varies proportionally with the cosine of the angle between the 〈111〉 axis and the direction of the field. This is in conformity with the results of neutron diffraction experiments. The maximum value of M (0) gives a value for the resultant magnetic moment of 13.6 μB per formula unit Fe5Ho3O12. The differential susceptibility in this direction is equal to 0.02 μB/kOe=1.27×10−4/g, and is larger in the other directions. The canted arrangement of the moments of the holmium ions is thus sensitive to the field in this temperature range.
Induced Anisotropy of Silicon-Doped YIG
Authors: Hunt Robert P. 
Published: April 2005

The induced anisotropy of single-crystal silicon-doped YIG (Y3Fe5−δSiδO12; 0≤δ≤0.18) was studied by means of a torque magnetometer. It was found that the annealed component of the torque could be adequately described by a free energy of the form Aan=−GΣ lim i&gt;iαiαjβiβj,  i,j=x,y,zwhere αi and βi, respectively, specify the direction cosines of M during measurement and anneal.
A model consistent with these observations was formulated. Specifically, it was assumed that the annealed anisotropy was caused by an ordering of the Fe2+ ions over the four types of magnetically inequivalent octahedral sites. Taking into account the interaction of crystal field, spin-orbit, and exchange interaction, a calculation of the energy levels of the octahedrally coordinated Fe2+ ion provides an eigenvalue spectra compatible with the symmetry and magnitude of Aan.
The Chain-A New Magnetic Film Memory Device
Authors: Leilich H. O. 
Published: April 2005

A copper strip plated with a nickel-iron film forms a new device for orthogonally switching word organized memories. The strip carries the word current. Bit-sense wires passing through holes in the strip determine the storage locations.
The device has closed flux in both word and bit directions, such that the film thickness, miniaturization, and bit packing density are not limited by demagnetization and stray field phenomena. Films of 25 000 Å thickness give signals of 500 mV·nsec which allow the use of slower rising read pulses and less gain bandwidth in the sense amplifiers relative to known thin-film devices. The configuration of the chain also enhances magnetic stability and permits nondestructive readout.
The characteristic impedance of the chain word line is strongly influenced by the film properties; stray fields and Ohmic losses are small. The bit-sense wire has a high impedance, very high bit density, and low attenuation; very large sense segments are possible.
The manufacture of chains can be done in a low-cost batch process, while the wiring of the array resembles the mass assembly process of ferrite core planes.
Sharp Films as Memory Elements
Authors: Barker P. D. , Torok E. J. 
Published: April 2005

The concept of sharp films results from a study of the behavior of the magnetization vector at the edge of a thin film. In that study it was shown that many of the effects of the demagnetizing field at the edge of a film can be predicted by assuming a local shape edge-anisotropy field, whose easy axis lies parallel to the edge of the film. According to this theory, square films have a low nucleation threshold because the edges of the film perpendicular to the easy axis have an edge anisotropy that subtracts from the ordinary field-induced anisotropy yielding a region of low resultant anisotropy. Sharp films are memory elements in which the angle between the film edge and the easy axis is everywhere small. Consequently, the resultant anisotropy field along the edge is the sum instead of the difference of the two anisotropy fields, and the nucleation threshold is high. In fact, reverse domains in these films generally form in the center rather than at the edge. Sharp films have typical Hc values of 3 Oe for films of 4½ to 5 Oe Hk, while the reversible limit (creep threshold for zero easy axis field) will be 0.1 Oe less than H̄k.
Since magnetization creep is the principle limitation of thin film memory elements and since sharp films have creep thresholds far larger than films of ordinary shape deposited on the same substrate at the same time, new fast, low-power NDRO memory modes are possible with sharp films. These modes involve rotationally switching the films from one saturated state to another and use fields that are ⅔ Hc and ⅔ Hk so that no unselected films are disturbed.
Coincident Current Magnetic Film Memories Using Locked Hard-Direction Films Having Microshape Anisotropy
Authors: Billing H. , Rüdiger A. , Schilling R. 
Published: April 2005

Specially prepared NiFe films allow information storage in two hard-direction stable states. Most promising are films with very narrow strips of alternating thickness (e.g. D0=200 Å, D1=400 Å, strip widths b≈10 μ). The Néel wall forces, and the microshape anisotropy introduced by the strips of alternating thickness provide extremely stable locked magnetization states in the hard direction. A bias field forces the Néel walls to align along the thickness slopes, thus completely eliminating creeping. These unique magnetic properties can be utilized for coincident current selection and a nondestructive readout in memories of high storage capacity.
A readout method is employed using two orthogonal high-frequency fields of different frequencies fx and fy, providing an output signal at the difference frequency fm=fx−fy. The readout amplitude differs by two orders of magnitude, depending on the information stored. Pulse measurements with a number of these films showed the feasibility of the method. No deterioration of the output signals was observed even after 108 read, write, or half-select cycles. An evaluation of possible speed and storage capacity is made, taking into account various sources of noise and disturb signals.
Rare-Earth Compounds with the Th3P4-Type Structure
Authors: Holtzberg F. , Methfessel S. 
Published: April 2005

Th3P4-type compounds occur in rare-earth systems with elements of Vth and VIth group of the periodic system. In general, the existence of Th3P4 compounds appears to be coupled with the formation of 1:1 compounds of the NaCl type in the same system. Analysis of I 4̄ 3d symmetry reveals certain similarities of atomic coordination and distances in both structures.
In RE3−xvxX4 (X=S, Se, Te) (0≦x≦⅓) the rare-earth ions occupy a defect Th3 lattice with a random vacancy distribution. With increasing vacancy concentration x, the materials change continuously from metals to insulators and interesting electrical, ferromagnetic, or superconducting properties have been observed. The Vth group elements, Sb and Bi, form metallic compounds without a homogeneity range and with the rare-earth ions on the P4 sites.
Magnetic Properties of the Terbium Oxides at Temperatures between 1.4° and 300°K
Authors: MacChesney J. B. , Williams H. J. , Sherwood R. C. , Potter J. F. 
Published: April 2005

The six terbium oxide phases whose compositions range between Tb2O3 and TbO2 have been prepared and their magnetic properties measured at temperatures from 1.4° to 300°K. The lower oxide phases (C and B polymorphs of Tb2O3, TbO1.715, TbO1.809, and TbO1.823) were prepared by equilibration at appropriate temperatures and oxygen pressures. TbO2 could not be attained by equilibration with molecular oxygen, even at pressures as high as 4000 atm. Instead it was formed hydrothermally at 162°C and 306 atm of perchloric acid (HClO4·2H2O). X-ray diffraction confirmed the crystallographic parameters published by Baenzieger et al.1 for these phases.
Measurements of magnetization vs temperature revealed that all of the phases with the exception of TbO1.809 exhibited long-range magnetic order. Ordering temperatures are as follows: Tb2O3 (C type) 2°K, Tb2O3 (B type) 7°K, TbO1.823 6°K, TbO2 3°K. Except for TbO1.823 the ordering is antiferromagnetic as evidenced by negative paramagnetic Curie temperatures and absence of remanence effects. In the case of Tb1.823, however, a remanence amounting to 2% of the magnetization value at 80 kOe was observed upon removal of the field. All of the magnetically ordered specimens exhibited metamagnetic behavior; wherein at fields above a critical value (≈2 kOe), observed moments exhibited a nonlinear dependence upon applied field. In the paramagnetic region, the calculated effective moment was close to the appropriate free-ion value.
Electron Microscopic Observation of Domain Wall-Inclusion Interactions in Iron
Authors: Johnson Charles A. , Glenn Richard C. 
Published: April 2005

Transmission electron microscopic observations of the dynamic behavior of domain walls in thin polycrystalline foils of iron containing inclusions of varying sizes have been carried out under conditions of known applied field.1 The field component in the plane of the specimen was varied over the range 0→±10 Oe, traversing hysteresis loops in times of the order of 10 sec.
The observations show that inclusions affect the mobility of domain walls not only through the formation of individual Néel spike domains, but also by acting as tie points for domain wall intersections and by the formation of ``ladder'' domain structures connecting closely spaced inclusions.
The detailed domain structures observed during the cutting of large (about 1 μ) inclusions by 180° domain walls correspond closely to the structures predicted by detailed theoretical models of this process.2
New domains are readily formed at grain boundaries. A frequently observed alternative to the cutting of an inclusion by a domain wall is the formation of one or more new domains in other parts of the same grain.
Continuity of the normal component of magnetization across grain boundaries is accomplished either by echelon structures of the sort observed in thin nickel platelets3 or by individual spike domains extending from the boundary. A 16-mm motion picture film illustrating these points has been prepared and was presented at the conference.
Anomalous Surface Heating Rates
Authors: Harrington R. E. 
Published: April 2005

Metals, semiconductors, and insulators, when exposed to the high irradiance produced by an arc image furnace, appear hot much sooner than predicted by heat theory. For an irradiance of 1500 W/cm2, the surface of the samples tested reached a temperature of 2000°K or more in a few milliseconds whereas the mathematical theory of heat conduction suggests that several seconds should be required. The existence of anomalously fast heating is confirmed by a variety of experiments. The observations are consistent with the results expected for a surface region of very low thermal conductivity.
Tests using a high-brightness flash tube (to obtain higher irradiances) show a ``saturation'' of reflectivity for smoked MgO, tantalum, and water-cooled platinum samples. The ``saturation'' can be qualitatively explained on the basis of thermal equilibrium of the surface region with the irradiance.
Effects of Annealing on Thin Gold Films
Authors: Kane Walter M. , Spratt James P. , Hershinger Lincoln W. 
Published: April 2005

As a part of a thin-film device study, an investigation was conducted of the conditions under which thin metal films cease to be continuous. This paper discusses the effects of annealing on thin gold films that were sandwiched between two evaporated layers of zinc sulfide.
The electrical resistance of films in the 60- to 80-Å thickness range was monitored during constant-temperature anneals in a helium atmosphere. A portion of the resistance-time curve is found to follow the relationship R=R0eαt, where α depends on the temperature according to the equation α=α0e−E/kT. Electron micrographs show that the resistance increase is due to the agglomeration of the films, and it is suggested that the latter equation defines an activation energy for migration of gold atoms. A value of E∼1.8 eV is obtained for this gold-zinc sulfide system.
Magnetic Shielding by Superconducting Niobium Tin Plates
Authors: Benaroya R. , Mogensen H. P. 
Published: April 2005

This work experimentally explores the effectiveness of magnetic shielding between superconducting Nb3Sn plates at 4.2°K in transverse magnetic fields up to 19.6 kG. At 19.6 kG the field exclusion obtained in the center between two 3.0×2.5×0.3-cm thick plates, separated from each other by 1.0 cm, was 17.9 kG. It has been found that flux jumps not only degrade the shielding capability of the plates but also give rise to nonsymmetrical field distributions. A relationship has been established between the applied field B1 and its critical rate of increase (dB1/dt)c, below which flux jumps do not occur for pairs of plates of various thicknesses. Flux jumps have been completely eliminated by keeping dB1/dt&lt;(dB1/dt)c.
Bean's model of current penetration into a high-field superconductor and the assumption of induced rectangular current loops have been successfully applied in calculating field distributions between the plates at medium and high applied fields. This model is not as successful at the early stages of plate magnetization where the current penetration is a small fraction of the total depth of the superconductor and the surface currents are appreciable. It has been found that the condition of field reversal external to the shielding volume can be minimized by the use of shunt iron in close proximity to the superconducting plates. Such a feature is desirable for the application of superconductor plate shields to a deflector system for a high-intensity variable-energy cyclotron.
Accuracy in the Use of Electron-Diffraction Spot Patterns for Determining Crystal Orientations
Authors: Laird C. , Eichen E. , Bitler W. R. 
Published: April 2005

It has long been known that transmission electron-diffraction patterns appropriate to low-index zone axes in thin crystals exist over several degrees of tilt from the exact orientations. In this work the magnitude of the errors in determining crystal orientation from spot patterns has been investigated using precisely oriented crystals prepared by vapor deposition and an electron microscope equipped with a goniometer specimen stage. It was observed that patterns of low-index orientations existed over ranges as high as 20° tilt, and were insensitive to the size of the area diffracted. Tilt ranges were observed to increase noticeably when the foils were plastically deformed. However, orientations accurate to 0.5° may be determined by weighting the pattern according to the intensities of the diffraction spots.
Elastic bending of the foils and ``polygonization'' bending due to dislocations help to explain why the relrods are so much ``longer'' than predicted on the basis of relaxation of the Laue conditions, using kinematic theory.
Nonuniform Emission of Thermionic Cathodes
Authors: Jansen C. G. J. , Venema A. , Weekers Th. H. 
Published: April 2005

The nonuniform emission of thermionic cathodes has been studied with an anode-hole scanning technique by means of which ``effective'' work-function distributions could be obtained. Using these ``effective'' work-function distributions, information has been gained about the fraction of the total cathode surface that actually determines the saturated emission. The knowledge of this fraction facilitates the physical interpretation of the emission constant AR, appearing when the experimental Richardson formula is used.
It is proved that different types of practical cathodes show marked differences in emission uniformity under space charge as well as under saturated emission conditions and as a function of their lifetime.
At several hundred hours of life, approximated values of the fraction of the surface area that determines the saturated emission and of its work function were found to be 0.35 and 1.81 V at 1350°K for an L cathode, 0.18 and 1.72 V at 1350°K for an impregnated cathode, 0.067 and 1.26 V at 1025°K for a (BaSr)O cathode.
Propagation of Bragg-Reflected Neutrons in Bounded Mosaic Crystals
Authors: Werner S. A. , Arrott Anthony , King J. S. , Kendrick H. 
Published: April 2005

The analysis of the multiple Bragg reflection of a neutron beam of finite size in a semi-infinite mosaic crystal given in a recent paper by Werner and Arrott is generalized to include bounded crystals. The coupled differential equations describing secondary extinction given by Hamilton are solved in general, and a method of piecewise solution, or solution by regions, is given.
A discussion is given of experiments on the spatial distribution of the diffracted current from slab-shaped crystals. Various methods for measuring the probability for Bragg scattering per unit path are compared and found not to agree. It is felt that the discrepancies are basic to the mosaic structure of crystals in general.
Dislocation Climb and Determination of Stacking-Fault Energies in Al and Al-1% Mg
Authors: Kannan V. C. , Thomas G. 
Published: April 2005

Quenching and annealing experiments on bulk specimens and hot-stage investigations of climb of loops in thin foils have been made on Al-1% Mg, and the results compared to those for pure aluminum. One percent Mg in solid solution has no effect on the type of loop produced after quenching nor on the precipitation of vacancies after subsequent aging. As in pure aluminum, quenching stresses determine whether Frank or perfect loops are formed in the alloy. Magnesium has little effect on the climb rate of loops, the activation energy being in the range 1.2–1.28 eV, which is similar to the values obtained by identical experiments on pure aluminum. It is concluded that the vacancy-magnesium-atom binding energy is extremely small.
The stacking-fault energies were estimated by comparing the rates of climb of large Frank and perfect loops in the same area of the foil so as to minimize the errors that arise if only the climb of Frank loops is measured. The stacking-fault energies were determined to be 190±10 erg/cm2 for Al-1% Mg and 210±10 erg/cm2 for pure Al.
Effect of Thermal and Ultraviolet Radiation on Thermionic Emission from Tungsten
Authors: Stickney R. E. , Sun P. B. , Shaw M. L. 
Published: April 2005

When thermal or ultraviolet radiation is focused upon a thermionic cathode, the resulting elevation of the cathode temperature causes the thermionic emission current to increase. Hence a thermionic diode may be used to measure radiation intensity, and it provides a convenient technique for measuring the spectral emissivities of materials at high temperatures. Also thermionic diodes may provide new techniques for detecting molecular beams and for studying chemical reactions at surfaces.
Reported here are experimental data on the effect of thermal and ultraviolet radiation on the electron emission from a tungsten cathode. At high cathode temperatures, the increase in thermionic emission produced by ultraviolet radiation is much larger than the photoelectric emission. The results are described by a simple expression derived from the Richardson equation for thermionic emission.