bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetostriction of Single-Crystal Dysprosium, Gadolinium Iron Garnet, and Dysprosium Iron Garnet
Authors: Clark A. E. , DeSavage B. F. , Callen E. R. 
Published: April 2005

The temperature and field dependences of the magnetostriction of dysprosium single crystals were measured from 78°K to room temperatures. In the paramagnetic region (T&gt;178°K), the six lowest-order coefficients were measured and were found to vary as H2. At lower temperatures, due to the large uniaxial anisotropy, only the basal plane coefficient was measureable. The temperature and field dependences of this coefficient are adequately represented by the single-ion magnetoelastic coupling theory and are given as a function of the moment by λ=8.7×10−3I5/2[L−1(m)].
The temperature dependences of the magnetostriction coefficients of single-crystal GdIG and DyIG were measured from 78° to 400°K and found to be much larger and of opposite sign than that of YIG over most of the temperature range. This is due to the larger magnetoelastic coupling coefficient of the rareearth ions. Among the several interesting features are: the observance of magnetostriction compensation points, the sharp dip (and change of sign) of the apparent saturation magnetostriction at the magnetization compensation points, and the reversal in sign of the forced magnetostriction.
Extinction of Gas-Shock Luminosity Against Transparent Surfaces
Authors: Plauson R. A. , Mallory H. Dean 
Published: April 2005

The use of explosively driven shock waves in argon or air is well known for the production of light in photographic studies of high-speed phenomena. It is shown that when high-intensity luminous shock waves are terminated against transparent surfaces, the light extinction curve is characteristic of both the shocked gas and the terminal surface. Some materials ``quench'' the light with great speed, possibly due to a metallic transition which blocks further transmission.
With nitrocellulose films the effect is transitory. Under the conditions of these experiments a gas over the specimen surface is a necessary condition for opacity. With properly prepared terminal surfaces and H2 as the shock-light source, light pulses of less than 1/15-μsec duration can be obtained from 13-mm gaps.
Injection Electroluminescence in ZnS and ZnSe
Authors: Aven M. , Cusano D. A. 
Published: April 2005

Injection electroluminescence has been observed in Cu2S-ZnS and Cu2Se-ZnSe heterojunctions. The light emission occurs through hole injection from the p-type Cu chalcogenide into n-type ZnS or ZnSe. At room temperature the light emission from the Cu2S-ZnS and the Cu2Se-ZnSe junctions originates at the Cu or self-activated luminescence centers. At 77°K the Cu2Se-ZnSe diodes exhibit emission bands peaking at 1.96, 2.07, 2.36, and 2.68 eV. The dominance of any one of these bands over the others can be achieved by appropriate preparative techniques. In the diodes emitting predominantly in the 2.36-eV band the light intensity varies approximately as the 32 power of current. The lowest voltage threshold observed for visible light emission is 1.5 V.
Both the luminescence and the electrical characteristics of the prepared diodes are in accord with a tentative model for the band structure of Cu chalcogenide-II-VI compound heterojunctions. The particular model for the Cu2Se-ZnSe diodes is presented and discussed in detail.
Web Growth of Semiconductors
Authors: O'Hara S. , Bennett A. I. 
Published: April 2005

A novel process for growth of diamond-lattice semiconductors is described, and a model is proposed for the growth mechanism. For germanium the process yields extended thin flat sheets, typically 1 cm wide and 0.1 mm thick, of good crystalline quality and relatively flat {111} surfaces. The sheet, or web, freezes from a liquid film drawn up by surface tension between two coplanar dendrites which originate from a single seed and are grown from the melt simultaneously with the sheet. Resistivity throughout the sheet is quite uniform. Etching of germanium webs shows them to be essentially dislocation-free and does not reveal any microsegregation of impurities. Silicon and indium antimonide have also been grown in this manner.
The proposed model postulates that although the dendrites at either side of the web grow beneath the melt surface in usual dendritic fashion, the faces of the web itself normally have no extension below the melt surface. The exterior contact angle between the solid and liquid surfaces is less than 180° but greater than the equilibrium contact angle which would be observed if the flat faces extended beneath the melt surface. In spite of this the grown faces are plane and vertical, thickening of the web being restricted by difficulty of nucleation. In this respect the predictions of this model are significantly different than for Čzochralski or floating-zone growth. Extensive experimental observations, including deliberately produced irregularities, verify the predictions of the model.
NDRO Magnetic Film Memory Mode Using Creep and Boundary Displacement Switching
Authors: Hoper John H. 
Published: April 2005

A new switching technique for thin magnetic films of Permalloy was investigated. Orthogonal ac fields were used instead of the usual pulse switching fields. Two variations of the transverse field were tried with ω=2π×106 rad/sec: hT=HT½(1−cosωt) and hT=HTsin(ω/2)t. The longitudinal fields (easy direction) were hL=+HL cosωt or −HL cosωt; hL or −hL was used depending on which remenant magnetic state of the film was desired. The time display of the vector sum (Liassajou pattern) of hT and hL formed a straight line or a parabola for the two transverse drive methods. With the correct combinations of hT and hL, the film would switch with both fields applied but would retain the previous state with only one of the two applied.
The state of the film was detected by applying the nondestructive hT and observing the phase of the output from a sense winding.
This switching mode appears to have utility in large, word organized memories.
Interaction between Magnetic Film Storage Elements
Authors: Bonyhard P. I. 
Published: April 2005

The effect of the dimensions and relative separations of storage elements upon interaction is considered in a plane geometry, word-organized, ferromagnetic thin-film computer store. Interaction consists of the switching of a fraction of the magnetization of the storage element and may result in the loss of stored information. Interaction between adjacent digits of the same word (digit interaction) and that between corresponding digits of adjacent words (word interaction) are distinguished. Interaction is measured by the reduction of the output voltage of the storage element.
An experiment is described in which interaction is measured using strip-line conductor patterns of different widths and pitches to define storage element in the same area of continuous magnetic film. The results show how word interaction increases as the pitch of the word lines is reduced and that digit interaction reduces as the word linewidth is reduced.
The interaction between elements in a continuous magnetic film is compared to that between discrete rectangles of film produced by etching or by masked evaporation. Discrete elements are found to give less word interaction especially if the film thickness is over about 800 Å. Films varying in thickness from a few 100 Å to a few 1000 Å are examined and the properties relevant to storage, and interaction in particular, are compared. Although there is not obvious correlation between interaction and film thickness for thinner films, both word and digit interaction increases with film thickness for thicker films.
The relevance of these observations in light of the known properties of thin magnetic films is discussed, with particular reference to domain wall creep. The magnitude of stray field which causes wall creep is estimated in three different experiments, two of which use the thin film element as monitor, the third being done independently of the film. All three estimates yield values considerably above the theoretical estimate.
In another experiment the adjacent film elements, whose switching causes interaction, are removed from the substrate. After the removal of the relevant elements no digit interaction is observed, while word interaction is not reduced.
Antiferromagnetic Resonance Linewidth in MnF2 near the Transition Temperature
Authors: Burgiel J. C. , Strandberg M. W. P. 
Published: April 2005

The antiferromagnetic resonance (AFMR) linewidth of MnF2 has been studied near the Néel temperature TN. In the presence of an applied magnetic field, the linewidth diverges as | T−TN |−56. In the absence of an applied field, the linewidth is larger and diverges approximately as | T−TN |−43. The linewidth is independent of magnetic field direction and is the same for both branches of the AFMR spectrum. Near TN the AFMR frequency varies as |T−TN|0.483±0.025 whereas the simplest molecular field theory predicts a |T−TN|½ variation. From this temperature dependence, together with existing data on the fluorine nuclear magnetic resonance in MnF2, we find that the anisotropy energy EA is proportional to M2.89±0.16 compared to Zener's M3 and Oguchi's M2.9 theoretical results.
Above TN, the electron paramagnetic resonance in MnF2 has been observed. For H0 ∥ c the linewidth varies as (T−TN)−3/8 near TN. For H0⊥c the linewidth increases more slowly as TN is approached.
Metallurgy of Oriented Silicon Steels
Authors: Wiener George W. 
Published: April 2005

For the past twenty-five years, a single oriented silicon steel containing 3% silicon has been commercially produced. The crystallographic description of this material is usually given as (110)[001]. It is now generally agreed that this texture occurs because of a preferred type of secondary recrystallization occurring at temperatures above 950°C. The primary recrystallization texture contains only a small fraction of the (110)[001] component which forms from a (111)[112] deformation texture. In order to complete the orientation process by secondary recrystallization, various impurities have been suggested. These impurities are in the form of a second phase. However, manganese sulphide has been found to be the most effective for providing conditions for selective growth of the (110)[001] component. Furthermore, at the desirable annealing temperatures, sulfur is rapidly lost by diffusion, thus, the final product is highly oriented and has excellent properties because of the low impurity level.
More recently, a cube texture (001)[100] has also been made by at least two techniques. By controlled columnar freezing of the ingot, a type of 〈001〉 fiber texture can be produced. If this structure is carefully cold rolled and annealed, eventually a primary recrystallization (100)[001] texture will result. Alternately the cube texture can also be achieved by a controlled surface energy reaction causing a secondary recrystallization. The primary recrystallization texture necessary for the production of a highly oriented product is obtained by rolling and annealing a (110)[001] type of orientation. The secondary growth of the (100)[001] grain is controlled by surface and grain boundary energies. A critical amount of sulfur is required in the steel to initiate the cube grains. However, an excess of either sulfur or oxygen will prevent the growth process. Elimination of oxygen to the lowest possible levels will favor cube growth providing that the sulfur content is in a critical concentration range.
If the sulfur content drops to too low a level, cube grain growth will also cease. The range of sulfur required for cube growth is orders of magnitude below the reported level of solid solubility.
Grain Size Effects in Silicon Steels upon the ac Core Loss Components
Authors: Lenhart R. E. 
Published: April 2005

For some time it has been recognized that the sum of the classical eddy-current core loss and the loss represented by the dc hysteresis loop does not equal the total core loss. This error has been referred to as the anomalous or unaccounted loss.
In recent years attempts have been made to account for this anomalous loss by utilizing modern domain concepts. It has been postulated that at small ratios of domain size to sheet thickness the anomalous loss should go to zero. Likewise at large ratios of domain size to sheet thickness, the eddy-current loss could be several times that predicted by the classical equation.
In an attempt to explore the effects of grain size upon core loss components, it was found that the anomalous loss was nearly independent of grain size at constant thickness. If it is assumed that the magnetic domain size increases with increasing grain size, these measurements refute the importance of the changing domain size in the modern domain eddy current theories. However, it was noted that the dc hysteresis loss portion of total core loss changes significantly with grain size.
Requirements for Developing Cube-on-Edge Texture in 4-mil-Thick Silicon—Iron
Authors: Fiedler H. C. 
Published: April 2005

Cube-on-edge grain oriented silicon—iron strip is widely used in electrical apparatus in thicknesses down to about 10 mils (0.25 mm). Lighter gauge strip, such as is commonly used at frequencies above 60 cps, is made commercially by cold rolling the normal gauge, grain-oriented material to the desired thin gauge and then recrystallizing. The requirements for developing the cube-on-edge texture directly at 4 mils (0.1 mm), as is done at thicknesses of 10 to 14 mils, have been determined using a laboratory-made heat, containing 3.3% silicon, 0.026% sulfur, and 0.06% manganese.
The development of cube-on-edge texture by secondary recrystallization depends upon the presence of inclusions to restrain normal grain growth. The effectiveness of inclusions in performing this function depends upon their size, which is determined by the prior thermal history of the material. The driving force for secondary recrystallization is inversely proportional to the radius of curvature of the primary grains. As the thickness of the strip decreases, the fraction of grains with a face on the surface of the strip increases and the average radius of curvature increases. Therefore, to maintain the driving force, the primary grain size must be decreased as the strip thickness is decreased. This is achieved during the prior hot processing of the ingot by increasing the cooling rate from the solution temperature of the inclusions, thereby obtaining a greater number of—and smaller—inclusions. It is shown that with a cooling rate of 130°C/min from the solution temperature, secondary recrystallization occurs in strip 4 mils thick as well as 12 mils. However, with a cooling rate of 50°C/min, secondary recrystallization occurs only in the thicker material.
The thinner the strip is the more readily are the inclusions prematurely lost during the texture-developing anneal. It is shown that only normal grain growth is obtained when 4-mil strip is heated in dry hydrogen, whereas complete secondary recrystallization is obtained when a wet hydrogen atmosphere is used. This is attributed to the diffusion barrier presented by a layer of silica on the surface.1
Ferromagnetic Resonance of Single-Crystal Gadolinium
Authors: Moore T. W. , Rodbell D. S. 
Published: April 2005

Gadolinium metal is a system of relative simplicity as far as exchange interactions and ionic states are concerned. The 8S7/2 state of Gd3+ is consistent with the observed 7μb/atom and the moment contributing f electrons are most likely exchange coupled via conduction electrons. The present work concerns the measurement of the ferromagnetic resonance behavior of a single crystal at frequencies of 21 and 35 Gc/sec and at temperatures from above the Curie point (20°C) to 4.2°K. The resonance absorptions are well defined at both frequencies and at all temperatures for most crystal orientations. The minimum linewidth observed is about 400 Oe but the line shape and width degrade when the applied field departs from the easy axis, particularly at the lower frequency and at low temperatures. Strong, well-defined domain wall resonances are also frequently observed.
The deduced magnetocrystalline anisotropy energy is accurately described by the standard uniaxial expansion EA = K1 sin2θ+K2 sin4θ+⋯, about the hexagonal axis. The anisotropy constants derived from the resonance data agree reasonably well with those measured by Graham1 using static torque methods. The samples used in these experiments are from the same source.2
The demagnetization fields at the surface of the coin-shaped sample are measured directly from the shift in the resonance field of a small chip of the free radical DPPH in intimate contact with the sample surface.3 The corresponding demagnetization factors lie between that calculated by Schlömann4 for a uniformly magnetized right cylinder (an accurate description of our sample shape) and that calculated for an oblate spheroid of the same axial ratio, tending toward the latter at low temperatures.
Using the magnetization measurements of Graham (as a function of temperature and applied field) we find that the spectroscopic splitting factor, g, is 2.00±0.02 below 0°C, changing smoothly to 1.94±0.02 at 28°C in the paramagnetic region. This latter values agrees well with those reported by Kip5 and by Popplewell and Tebble.6 The g value at low temperatures, also deduced from the resonance data, gives better (but still not exact) agreement between the directly measured saturation magnetization and that implied by the 8S7/2 ionic state.
Observations of the Ordering Process in a Mg–Fe Ferrite
Authors: Heck Carl , Vaccari Gianantonio 
Published: April 2005

Slowly cooled magnesium-iron ferrites of the approximate composition MgO2FeO·4Fe2O3 have constricted hysteresis loops in a wide range of temperature. Applying a magnetothermic treatment one can induce an anisotropy which is accompanied by a square hysteresis loop. The speed of the ordering process can be varied in a certain range by variation of the temperature. The treatment of samples was performed at about 100°C allowing an exact study of the process.
During the conversion of the shape of the hysteresis loop the remanence ratio Br/Bm increases. An activation energy of 0.37 eV can be derived from the temperature dependence of this change. This is in good agreement with results of Sixtus.
More exact investigations revealed an unexpected effect; the peak induction increases with time discontinuously in two main steps while the field is kept constant. The time at which the steps occur varies with temperature. An activation energy of 1.4 eV can be derived.
Nearly the same value was calculated from the temperature dependence of an observed minimum of the magnetization energy occurring during loop transformation. The depth of this minimum can be taken as a measure of the induced anisotropy.
Flux Reversal in Rare-Earth-Substituted Yttrium Iron Garnets
Authors: Palmer Wilfred 
Published: April 2005

The switching properties of polycrystalline toroids of pure YIG (yttrium iron garnet) and YIG containing 1% Dy, 3% Dy, and 4% Sm have been measured over the temperature range 4.2° to 300°K. In each of the rare-earth-substituted materials, the field required to switch 50% of the flux in a given time shows a peak at a temperature which is approximately 0.4 times the temperature at which a peak is observed in the ferrimagnetic resonance linewidth. It is assumed that at low switching speeds flux reversal occurs by domain wall motion, and an explanation of the temperature dependence of the switching field is sought in a consideration of the effect of the loss mechanisms which determine the linewidth on the domain wall mobility. The field above threshold H − H0 required for complete dissipation of magnetostatic energy in the moving wall at a given domain wall velocity V, and thus a given switching speed, should be proportional to the linewidth at the effective precession frequency applicable to domain wall motion. For 180° domain walls this frequency is approximately Vπ/d, where d is the domain wall thickness. Measurements of the frequency dependence of the linewidth of rare-earth-substituted YIG have indicated that the loss mechanisms in these materials are ``slow'' relaxation processes. For slow relaxation processes the linewidth is given by the expression ΔH (T, ωτ) = F (T)ωτ/1+ω2τ2, where ω is the experimental frequency and τ is the relaxation time. H − H0 (T, Vπτ/d) should depend in a similar way on Vπτ/d. This requires that Vπτ/d be a double-valued function of H − H0, the higher value of which is inaccessible. The increase of ωτ beyond unity contributes to the decrease of the linewidth at low temperature, but the decrease in the switching field at low temperature cannot be explained in this way. If the switching time chosen for reference were sufficiently short that at low temperatures Vπτ/d increases beyond unity, the required field would not be reduced but a discontinuous increase in switching speed, which is not observed, would occur at the field H − H0 (T, Vπτ/d=1). However, the behavior of the switching field is understandable if the explicit temperature dependence of H − H0 (T, Vπτ/d) is such as to produce the observed decrease at low temperature.
A report of this work and related topics has been submitted for publication.
Interactions between Ni and NiO
Authors: Berkowitz A. E. , Greiner J. H. 
Published: April 2005

Polycrystalline Ni films, evaporated onto single-crystal NiO substrates, have been studied by torque measurements from 77° to 473°K in fields up to 22 kOe. The NiO films had (111) and (001) orientations, representing planes of parallel and compensated spins, respectively. After short vacuum anneals above TN, the Néel temperature, the major torque symmetry of the films on (001) NiO substrates was sin 4θ with an amplitude that decreased with increasing field. This was due to the rhombohedral distortion of NiO below TN; a (001) crystal consists of twinned, T-domain regions. This oriented strain field in the NiO substrate propagates into the Ni film and produces two orthogonal uniaxial anisotropies by a strain-magnetostriction mechanism.
The (111) NiO substrates were also twinned. After annealing above TN, the Ni films on these substrates showed a peak in the rotational hysteresis at ∼1 kOe, and a torque component of sixfold symmetry in the moderate to high-field range. One sample also showed rotational hysteresis that was increasing rapidly at 22 kOe. This behavior is consistent with a model involving exchange anisotropy, the motion of T-domain walls, and a strain-magnetostriction mechanism.