bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Wave Resonance and Plasma Instability in a Cesium Discharge
Authors: Decker John A.
Published: April 2005

Coherent audiofrequency electrostatic oscillations were directly observed in the probe noise of a cesium glow discharge at pressures from 10−2 to 10−5 Torr and magnetic fields up to 4500 G; observed oscillation frequencies corresponded to frequencies for classical ion waves, as proposed by Tonks and Langmuir, in resonance with the discharge tube length. In addition, the discharge was extinguished coincidently with a rapid growth of wave amplitude if the current or magnetic field was increased above critical values. This has been tentatively identified as a helical plasma instability of the type first suggested by Kadomtsev and Nedospasov, although the observed correlation between instability onset and wave growth has not yet been satisfactorily explained.
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.
Secondary Positive Ion Emission from a Tantalum Surface
Authors: McHugh James A. , Sheffield James C.
Published: April 2005

The secondary positive ions ejected from a tantalum target by a mass-analyzed primary beam were detected and studied in a mass spectrometer. The secondary ion emission consisted of species characteristic of the metal (Ta+), metal compounds (oxides), and multiatomic ions of the metal (Ta2+, Ta3+). Reflection of normally incident gas ions from the Ta surface was not observed; the specular reflection coefficient of ions to ions is then less than 10−6. The relative secondary ion yields for tantalum, measured for normally incident Hg202 ions at energies between 0.3–14 keV, were independent of the incident ion charge. A dependence of the Ta+ secondary yield on mass of the incident ion was observed. The dependence of the secondary ion yield on mass and energy of the incident ions was very similar to that observed for total sputtering yields.
Mathematical Treatment of Competitive Surface and Volume Diffusion Processes
Authors: Amar Henri , Drew James B.
Published: April 2005

Equations are derived for the surface diffusion of atoms into a half-plane (the boundary of which is kept at constant concentration) under conditions in which atoms are simultaneously being lost into the bulk via a volume diffusion mechanism. Two coupled boundary valued problems arise which are solved by treating the volume diffusion as a perturbation. Methods of evaluating the coefficient D8 of surface diffusion are discussed. The final surface concentration Ŝ resulting from the parasitic effect of volume diffusion contains three leakage terms. These terms have the effect of altering the time dependence of the concentration. This formulation is useful in interpreting surface diffusion data obtained in the high-temperature range.
Vapor-Deposited Superconductive Films of Nb, Ta, and V
Authors: Neugebauer C. A. , Ekvall R. A.
Published: April 2005

The strong gettering action for oxygen or oxygen-containing gases displayed by Nb, Ta, and V was used to reduce the partial pressure of these gases in a vacuum system; and allowed deposition from the vapor of superconducting thin films of these metals even at pressures of the residual gases higher than 10−5 Torr provided elevated substrate temperatures were used. Critical temperatures of the films were as high or higher than those of the bulk materials; the highest values were T(Nb)=9.81°±0.05°K, T(Ta)=4.51°±0.05°K, T(V)=6.02°±0.10°K. Electron tunneling experiments demonstrated that the size and temperature dependence [ε(0)=3.5Tc] of the energy gap of these films is in good agreement with the BCS theory. Critical current vs magnetic field measurements at 4.2°K indicate that Ta films go normal at 220–240 Oe and Nb films at 9–15 kOe. Films of niobium prepared at low-substrate temperatures displayed inflated lattice parameters and were not superconductors.
Ferrimagnetic Garnets Containing Pentavalent Vanadium
Authors: Geller S. , Espinosa G. P. , Williams H. J. , Sherwood R. C. , Nesbitt E. A.
Published: April 2005

Magnetic and crystallographic data are reported on the system {Y3−2xCa2x} [Fe2] (Fe3−xVx)O12. It appears that for all values of x, 0< x ≤1.5, Curie temperatures are higher than would have been expected. To x≅0.7, the Curie temperatures are equal to or slightly greater than that of yttrium iron garnet (YIG) itself, then decrease gradually to 493°K for {Ca3} [Fe2] (Fe1.5V1.5)O12. Garnets in the system {Bi3−2xCa2x} [Fe2]-(Fe3−xVx)O12 with 1.5>x>0.8 exist. The magnetic behavior of the garnet {Bi0.5Ca2.5} [Fe2] (Fe1.75V1.25)O12 is essentially the same as that of the yttrium analog. Pentavalent vanadium substitution thus provides lower moment garnets with high Curie temperatures and including Bi3+ ion substitution, ferrimagnetic garnets not containing rare earths or yttrium.
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.
Thermoelectric Power of Hot Carriers
Authors: Zucker J.
Published: April 2005

Measurements made at room temperature of the thermoelectric effect of hot carriers in n- and p-type germanium excited by the application of strong 2.85-Gc/sec microwave fields have been analyzed by applying the usual theory of thermoelectric power to the case of hot carriers. The carrier temperature Te and the energy relaxation time τe have been calculated from the data. For the carrier temperature equal to the lattice temperature (T0=300°K) the energy relaxation time for pure n-type germanium was 13.4×10−12 sec, while that for pure p-type germanium was 4.9×10−12 sec. In both cases τe fell with rising carrier temperature, to about 0.55×10−12 sec for the n-type germanium for Te>3T0 and to about 0.4×10−12 sec for the p-type germanium sample at Te=2.5T0. In both cases there were oscillations in the curves of energy relaxation time vs carrier temperature and ratio of energy relaxation time to momentum relaxation time vs carrier temperature. An explanation of this effect is based on energy loss via optical modes.
Influence of Oxygen on the Surface Mobility of Tin Atoms in Thin Films
Authors: Caswell H. L. , Budo Y.
Published: April 2005

Tin films less than 800 Å in thickness deposited on 78°K substrates were found to be continuous at low temperatures but to agglomerate into discontinuous islands upon warming to room temperature. Any stage in the agglomeration process could be stabilized by admitting oxygen at a pressure of 10−4 Torr and warming the film to room temperature in the presence of oxygen. Electrical resistance data indicate the surface mobility of the tin is reduced by the formation of a surface oxide one to two monolayers in thickness and that there is no appreciable diffusion of oxygen into the bulk of the film material.
X-Ray-Induced Dislocation Generation in Sodium Chloride
Authors: Wolfe Robert L. , Bauer Charles L.
Published: April 2005

The strain distribution, induced by subjecting one-half of a sodium chloride single crystal to x rays while shielding the other half, has been investigated with a dislocation etch pit technique. Due to the expansion of the irradiated half, a strain gradient arises antisymmetrically about the plane of the interface that is sufficient in magnitude to cause plastic deformation in the protected half, but not in the irradiated half of the crystal. The plastic deformation takes the form of a number of high-density dislocation bands which tend to align in a [100] direction. The bands increase in number but not appreciably in size as irradiation proceeds. The absence of plastic deformation in the irradiated half can be explained by the fact that irradiation raises the yield strength to such a level that the strain is not sufficient to induce plastic flow. In the protected region, however, dislocations are generated and glide until they impinge, causing discrete bands to form roughly parallel to (100) planes. From an analysis of the data, an estimate of the magnitude of the strain produced at the interface and the relationship between the strain and the number of F centers generated can be obtained. The results, although in some ways unexpected, are consistent with previous experiments performed on x-irradiated alkali halides.
Cationic Distribution in Cobalt Spinels
Authors: Richardson James T.
Published: April 2005

The molecular field treatment of the cobalt spinel CoxmN(1−xm)[Co(1−x)m N2−(1−x)m]O4 yields, for the high-temperature approximation, Curie—Weiss constants of the form μ2=xμA2+ (1−x)μB2 and θμ2/m = A+Bx+Cx2, where μA and μB are the magnetic moments of Co2+ on tetrahedral and octahedral sites, respectively, and A, B, and C are related to the exchange integrals. Magnetic measurements were made in Co2GeO4 and CoAl2O4, whose cationic distributions were determined by x-ray diffraction, to establish values of μA and μB as 4.31β and 4.88β, respectively. These values are in agreement with those expected from crystal field considerations and were confirmed by measurements on Co2TiO4, whose distribution is known. The cation distribution parameter x was then determined from the magnetic moment measurements of the series ComZn2−mTiO4 and ComMg2−mTiO4. It was found that Zn2+ replaces Co2+ exclusively on A sites, whereas Mg2+ substitutes equally on A and B sites, both as expected. The experimental values of θ, μ, and x for all samples followed the expression given above, with the constants A, B, and C yielding values of the exchange integrals for A-A, A-B, and B-B interactions.
Graphite Defects Observed by Electron Microscopy
Authors: Bonfiglioli G. , Mojoni A.
Published: April 2005

Structural defects of natural graphite are characterized by Newton-ring-like electron microscopic contrast. Pictures are given, evidencing their aspect, their peculiar distribution (often corresponding to linear alignment), and their behavior at high temperatures. A discussion is presented concerning related theoretical and experimental results of other authors and in particular the relationship of these defects to radiation damage.
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.
Effect of Growth Rate on Stacking-Fault Density in Epitaxial Silicon Layers
Authors: Notis M. R. , Conard G. P.
Published: April 2005

The growth rate of an epitaxial silicon deposit affects the stacking-fault density of the deposited layer in a linear manner over the deposition range of 0.1 to 1.0 μ/min. The stacking-fault density is also inversely related to the substrate dislocation density for dislocation densities up to 5×103 cm−2. The conditions for the formation of stacking faults, as described by various authors to date, seem sufficient but not necessary for fault formation. The present work supports a vacancy condensation mechanism by which the low stacking-fault energy of the material creates a natural condensation of vacancies into stacking faults.
Detonation Initiated by High-Pressure Gas Loading of a Solid Explosive
Authors: Price Donna , Petrone Francis J.
Published: April 2005

A one-dimensional numerical treatment reproduces experimental trends observed in the shock initiation of solid explosives; it has consequently been used to show that a rapid gas loading of a solid explosive to the initiating pressure for its charge configuration effects detonation. The deflagration-to-detonation experiments (pressure generated by confined burning of cast explosives) and air-gap sensitivity tests (pressure generated by gaseous detonation products of an explosive donor) are examples of detonation caused by gas loading.
Fermi Surface of Nickel from Galvanomagnetic Measurements
Authors: Reed W. A. , Fawcett E.
Published: April 2005

Measurements of the high-field galvanomagnetic properties of nickel show that one electron-sheet of its Fermi surface is multiply connected, and touches the {111} faces of the Brillouin zone as does the Fermi surface of copper. In magnetic fields up to 80 kOe applied in a nonsymmetry direction, the magnetoresistance saturates and the transverse voltage is linear, the Hall constant corresponding to one electron per atom within the experimental accuracy. The last result strongly suggests that nickel is uncompensated, and if so it is a direct consequence of the removal of the spin degeneracy of the d bands by the ferromagnetic exchange interaction. According to this explanation, one, and only one, sheet of the Fermi surface in a spin zone (i.e., a half-band consisting of the states of a single sign of spin) of the 3d bands has an electronic character. The alternative explanation that the d bands contain only holes with a mobility at least two orders of magnitude smaller than the s-band electrons, cannot yet be conclusively ruled out but seems most unlikely. This study of nickel has shown that the experimental methods used to investigate the Fermi surfaces of nonmagnetic metals may be taken over directly to determine the Fermi surfaces of the ferromagnetic metals.
Low-Current, High-Speed Magnetic Memory Array Utilizing Evaporated Matrix Wiring
Authors: Matcovich T. J. , Flannery W. , Luciw W. , Adomines A. A.
Published: April 2005

Planar, thin film magnetic memory arrays of 4×4 and 64×24 elements have been fabricated from evaporated matrix wiring and insulating layers. Four metallic and three insulating layers were evaporated sequentially in a vacuum chamber without breaking the vacuum. The magnetic element is an electroplated ternary alloy of nickel-iron-phosphorus 0.13 mm (0.005-in.) in diameter and a few hundred Å thick. The film has an anisotropy field of about 1 Oe and switches in 10 nsec with an applied word drive current of 35 mA. Sense and cancellation lines and dummy bit lines are used to cancel interwire coupling. Disturb tests were performed with up to 104 disturb pulses being applied along the easy axis. The outputs from films with Hc/Hk≈2 were decreased by less than 10% when disturbed in this manner. An evaporated memory array made with highly inverted films may be usable as a high-speed, low-current memory storage device.
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.
Magnetoresistance and Hall-Voltage Measurements on Single-Crystal Ni and Ni-Fe Thin Films
Authors: Marsocci Velio A.
Published: April 2005

Measurements were taken at room temperature and at liquid-nitrogen temperature of the magneto-resistance of nickel and nickel-iron alloy thin films. The transverse magnetoresistance data, with current in a [110] direction, of Δρ/ρ0 vs θ, where θ is the angle between the plane of the film and the direction of the magnetic field, show marked anisotropies with large lobes at values of θ corresponding to the magnetic field perpendicular to a 〈111〉 direction of the crystal structure. Similar measurements performed on a polycrystalline film show quite an isotropic behavior. With the films at the low temperature (77°K) the graphical plot of Δρ/ρ0 shows the same general shape as that for the room-temperature data, except that for the nickel films Δρ/ρ0 is reduced in magnitude. No corresponding anisotropies were observed, however, in the Hall-voltage measurements which were taken at room temperature. The anisotropies observed in the magnetoresistance data for the nickel-iron alloy films were of the same general character as those observed for the nickel films.
Effect of Nonuniform Magnetization on the Spin-Wave Spectrum in Thin Ferromagnetic Films
Authors: Davies J. Tudor
Published: April 2005

It was first suggested by Portis that the linear positioning of the first few spin-wave modes observed in some ferromagnetic films could be due to a nonuniform static magnetization M and he examined a simple model which showed this effect. This model, where the magnetization falls parabolically from the film center, has been studied in greater detail. The modes found by Portis are incorrect in detail, since they all collapse onto the uniform mode as the distortion of M goes to zero. A more suitable choice of boundary conditions gives rise to a spectrum where the lower modes are linearly positioned whereas the higher modes tend to the more usual quadratic positioning. For a given relative distortion, the number of linear modes should be greater the thicker the film. This is in agreement with the measurements of Kooi, Wigen, and Nisenoff on Permalloy films, though the transition between linear and quadratic positioning observed by Nisenoff is much more abrupt than this model predicts.
Ferromagnetic Resonance Linewidth and Internal Biasing Field in Ni-Fe Films as a Function of Dispersion in the Anisotropy Field Magnitude
Authors: Nelson Roger H.
Published: April 2005

Ferromagnetic resonance techniques have been used to measure the magnetic properties of Ni-Fe films in the 50–1500 Mc/sec range. Resonance was observed in the plane of films 8 mm in diameter and 600–2600 Å thick. The primary purpose of the investigation was to obtain a correlation between the resonance linewidth extrapolated to zero frequency (ΔH)0, and the dispersion in anisotropy field magnitude Δ90. The zero-frequency linewidths found were about 2.8 times the values calculated theoretically from values of anisotropy field magnitude dispersion independently obtained in this laboratory. Plots of the resonance frequency squared as a function of resonance field showed a shift, or internal bias Hi, toward positive field values as others have observed. There was little or no shift for films with Δ90 less than about 0.2, but for larger dispersion, the shift increased approximately linearly with Δ90. A very good linear correlation was found between Hi and α0, the high-frequency damping parameter. It is suggested that the internal biasing field may be associated with the magnetization rippling that Fuller and Hale and Feldtkeller have observed in electron micrographs. Also, it may be possible that the larger-than-expected values of (ΔH)0, and the wide variation in α0 values (0.006–0.03) reported here are caused by the energy loss, which Feldtkeller has termed ``ripple hysteresis,'' associated with the movement of the small-angle walls, which result from the magnetization rippling.
Temperature Dependence of Domain Wall Creep in Thin Ni-Fe Magnetic Film
Authors: Sweet Marvin E.
Published: April 2005

This paper presents the results of an experimental program undertaken to determine the temperature dependence of the creep of magnetic domain walls in a uniaxial thin Ni-Fe magnetic film and its relationship to the temperature dependence of the anisotropy field (Hk), the coercive force (Hc), and the critical fields required to initiate domain wall motion. The temperature dependence of creep velocity is measured with a peak transverse ac magnetic field (HT ac) applied in the hard direction of magnetization and a dc longitudinal field (HL) applied in the easy direction. Measurements were made on a vacuum deposited thin film, 1613 Å thick with a composition of 82.2% Ni and 17.8% Fe, using the longitudinal Kerr magneto-optic effect. The thin film temperature was maintained to within ±0.8°C over the range 8.9 to 81.7°C. Experimental results show that domain wall creep velocity and the magnetic properties of the film are temperature dependent and that the temperature dependence of the former is related by a transformation to the temperature dependence of the latter. Curves of creep velocity, Hc, Hk as functions of temperature are given, and experimental and constructed curves of constant creep velocity were plotted at several temperature values to show that a correlation exists between the experimentally measured values and the calculated values.
Magnetization Curling in Tapered Edge Films
Authors: Hornreich Richard M.
Published: April 2005

A 90° curling of the magnetization occurs at those film edges perpendicular to the easy axis in films of 700–1800 Å thickness when the film edges are suitably tapered. This configuration replaces the closure domain state generally found at the edges of films in this thickness range. Theoretical calculations yield expressions for the preferred edge taper angle and the resultant distance in which the magnetization curling takes place. The expressions for the edge taper angle and the curling distance are given in terms of the anisotropy, exchange, and magnetization constants and the film thickness. The curling distances that occur in actual films are measured and found to be in good agreement with the theoretical predictions. Experiments showing the differences in switching behavior of tapered and nontapered films are described and correlated with theory.
Domain Structure of Narrow Thin Films of Ni-Fe
Authors: Kuwahara K. , Goto T. , Nishimura A. , Ozaki Y.
Published: April 2005

Narrow thin films of 80 Ni-20 Fe were produced by evaporation onto a glass substrate with a mask having several slits. The films were 15∼300 μ wide, 400∼1500 Å thick, and 4∼80 Oe in HK perpendicular to their long direction. Bitter patterns on the films having HK of several Oe showed the closure domains as proposed by Kittel. The energy density of the 180° walls between the adjacent main domains was measured to be 0.8 erg/cm2, by observing the spacing of the walls and the width of the films. The films having higher HK did not exhibit closure domains but only 180° walls parallel to the easy axis, as was also proposed by Kittel. By bending the substrate mechanically, HK was increased in the films having closure domains. The transition, from the structure of closure domains into that of no closure domains, was observed as expected.
Lorentz Microscopy of Magnetic Domains of Single-Crystal Films
Authors: Sato H. , Astrue R. W. , Shinozaki S. S.
Published: April 2005

Domain patterns of epitaxially grown iron single-crystal films are investigated by the Lorentz microscopy technique. The width of 180° walls appear much wider than that of 90° walls. Double 90° walls and the fine structure of 180° walls, such as Bloch lines, etc., are observed.
Origin of Biaxial Anisotropy in Polycrystalline Films
Authors: Prosen R. J. , Gondō Y. , Gran B. E.
Published: April 2005

A fourfold symmetry of anisotropy is found in polycrystalline films evaporated on unidirectionally scratched glass substrates. The origin of the biaxial anisotropy is attributed to a shape effect resulting from fine structure of the scratches. In essence, the fine structure of films deposited on such substrates is an array of oriented rectangularly shaped areas as confirmed by electron microscopic observation. Such arrays are simulated by depositing polycrystalline films by several methods in a regular array of small, discrete squares. Torque curves of the films have a large sin4θ component with the easy directions along the diagonals of the squares. The biaxial anisotropy constant estimated from the torque curves has the maximum value at a low measuring field and does not extrapolate to zero at high fields. Orthogonal switching experiments at low fields, where the magnetization rotates by 90° instead of 180°, also confirm the biaxial anisotropy related to the square shape. Based on these results, a domain configuration in the small square film at low fields, that consists of a central closure domain with an outer unclosed region, is proposed.
Stress Effects in Evaporated Permalloy Films
Authors: Pinch H. L. , Pinto A. A.
Published: April 2005

The magnetic properties of evaporated Permalloy films subject to external uniform stresses were experimentally determined and the resulting changes in magnitude and direction of HK were compared to recently reported theories. In general, qualitative agreement between the data and theory was found when the angular dispersion resulting from the stress was small. When the stress induced dispersion was large the discrepancies between data and theory become quite large. Some of the discrepancy in HK may be due to instrumental difficulties in measuring HK under conditions of large angular dispersion. The variation of HC with stress follows that of HK, but in a much less sensitive manner. When HK exhibited a minimum, HC showed a corresponding minimum while the dispersion and the hard axis coercivity had corresponding maxima. The stress-induced interchange of the easy and hard axes was found to proceed partially through a rotation of axes and not by just the anisotropy decrease predicted by theory. The axis rotation under these conditions is due to the excessive angular dispersion, the nonuniform nature of films, and the slight differences between the effects of tension and compression.
Temperature Dependence of the Sublattice Magnetization in Ferrimagnetic MnFe2O4
Authors: Heeger A. J. , Houston T.
Published: April 2005

The temperature dependence of the A-site sublattice magnetization in ferrimagnetic MnFe2O4 has been measured by observing the temperature dependence of the Mn55 NMR frequency. The initial deviation from saturation is proportional to T32 but no T52 term is observed. These results are found in agreement with a ferrimagnetic spin-wave calculation for the spinel lattice. Two T52 terms of opposite sign originate from the k4 terms of the dispersion relation and the k-dependent transformation coefficients from single sublattice spin-deviation operators to the diagonal spin-wave variables. These two terms cancel, for the spinel lattice, to within 1%.
Magnetic Field Quenching of the Suhl-Nakamura Width in Antiferromagnets
Authors: Pincus P.
Published: April 2005

In a magnetic material, the nuclear spins are coupled via the exchange of virtual magnons (Suhl-Nakamura interaction). At low temperatures this interaction is mainly transverse, i.e., Ii+Ij−, and is a main contributor to the transverse nuclear relaxation time T2 in materials with high concentrations of nuclear spins. If an external dc field, comparable to the nuclear hyperfine field, is applied perpendicularly to the direction of sublattice magnetization in an antiferromagnet the indirect interaction tends toward a scalar form. The scalar part of the interaction has a vanishing second moment and thus does not contribute to the linewidth; in fact, this term gives rise to a small exchange narrowing of the NMR line. For the F19 resonance in materials, such as FeF2 where the hyperfine field is only of the order of 40 kG, such a narrowing may be observable in moderate fields (∼20 kG).
Theory of Antiferromagnetic Resonance Absorption in CoF2
Authors: Kamimura H.
Published: April 2005

The effective spin Hamiltonian for the interaction between the fictitious spins of the lowest Kramers doublets in CoF2 is derived. The spin-wave spectra are then derived for a two-sublattice model in which the spins point along the ±c directions. Only one antiferromagnetic resonance frequency is obtained in the absence of magnetic field. In the presence of a magnetic field applied along the c axis the resonance line is split into two. In CoF2 the anisotropy arising from the crystal field has an important effect on the magnitude of the resonance frequency. The discrepancies between this theory and recent experiments suggest that several other mechanisms, which are pointed out, should be considered.
Mn55 Nuclear Magnetic Resonance in Antiferromagnetic RbMnF3
Authors: Heeger A. J. , Teaney D. T.
Published: April 2005

The observation and study of the Mn55 nuclear magnetic resonance in antiferromagnetic RbMnF3 at low temperatures are reported. The direct detection is possible because of a large enhancement of the signal from one of the NMR modes in a low anisotropy antiferromagnet above the critical field for spin flopping. Large frequency pulling effects are observed, and found to be in excellent quantitative agreement with theory. The unpulled NMR frequency has been determined as 687 Mc/sec at 2°K, and the corresponding linewidth is 60 kc/sec. An anomalous increase in linewidth with decreasing field and temperature is described.
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.
Experimental Determination of Permeability-Stress Relationships
Authors: Mendelsohn L. I. , Orth E. D. , Robbins P. A.
Published: April 2005

Large variations in permeability are probable in most soft ferromagnetic materials subjected to stress. The magnitude of these variations depends on the direction between the applied magnetizing force and the stress. In this paper techniques are described for measuring the ac permeability under two different stress conditions. μ∥ symbolizes the permeability when magnetizing force and induction are both parallel to the applied stress; μ⊥ when they are both perpendicular to it. Of the materials investigated, those which have positive magnetostrictive coefficients show their maximum permeability change when magnetizing force and stress are at right angles to one another. For nickel, which exhibits negative magnetostriction, the maximum permeability change occurs when magnetization and stress are collinear. Permeability values, μ∥ and μ⊥, for ingot iron, nickel, Nicaloi, and Hy-mu 80 are tabulated after the first stress cycle from 0 to 12 000 psi (850 kg/cm2), and at zero stress after two additional cycles. The difficulty with predicting permeability changes from magnetostriction concepts alone is exemplified by Hy-mu 80, a 79% Ni-17% Fe-4%Mo alloy, which has a low magnetostrictive coefficient. Based on this fact alone one would not predict the variations observed in μ⊥ from 14 000 at zero stress to 3800 at 12 000 psi. A great deal more theoretical and experimental work will be required on stress-permeability relations before quantitative generalization is possible.
Induced Magnetic Anisotropy and Ordering in Ni—Fe Single Crystals
Authors: Takahashi Minoru , Sasakawa Tetsuzo , Fujimori Hiroyasu
Published: April 2005

The temperature dependence of the induced magnetic anisotropy by magnetic annealing has been measured in Ni—Fe single crystals containing 91.0%, 74.6% (Ni3Fe), 69.0%, and 65.6% nickel. The ratios of the coefficients of the induced anisotropy energy, k2/k1, were almost constant with annealing temperature and had the value of 8.7 for Ni3Fe, 3.9 for 69.0% Ni and 2.3 for 65.0% Ni in disordered state while these values changed remarkably when specimens were annealed just below the order—disorder transition temperatures. This result cannot be explained by the atomic orientation theory based on the crystal structure even though higher approximation methods are used.
Investigations of the Effects of Neutron and He3 Irradiation on the Magnetic Properties of Permalloy Thin Films
Authors: Schindler A. I. , Williams C. M.
Published: April 2005

Measurements have been made of the changes in the magnetic anisotropy energy and hysteresis loop parameters of evaporated Permalloy thin films resulting from 2.2-MeV He3 irradiation and from reactor neutron irradiation. Only minor changes were observed following an irradiation of 1.6×1014 He3 particles/cm2. However, a total irradiation of either approximately 1017 neutrons/cm2, or 8 to 9×1016 He3 particles/cm2, yielded the following general results: Regardless of the magnetic state of the sample, the uniaxial anisotropy energy Ku increased (up to 200%) when irradiations took place in zero applied field. Similar increases were noted as a result of either neutron irradiation with a saturating magnetic field along the easy axis or He3 irradiation with a saturating magnetic field either parallel or perpendicular to the easy axis. A decrease of ∼50% in Ku resulted from neutron irradiation when the saturating magnetic field was applied perpendicular to the easy axis. Rotation of the easy axis, up to 78°, occurred for either neutron or He3 irradiation with a saturating magnetic field applied perpendicular to the easy axis. The more significant hysteresis loop modifications observed were the development of constricted loops (measured in the hard direction) for most of the samples irradiated in zero applied field, and decreases in the coercive force up to 28% (measured in the easy direction) of most of the irradiated samples.
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
Effect of Rare-Earth Impurities on the Ferrimagnetic Resonance and Nuclear Relaxation in Yttrium Iron Garnet
Authors: Hartmann-Boutron F.
Published: April 2005

The ferrimagnetic resonance anomalies of Yb-doped yttrium iron garnet have been satisfactorily interpreted recently with the aid of the so-called ``slow relaxation theory.'' In an attempt to relate this theory to that of ``fast relaxation,'' we begin by relating the anomalous properties of the impure garnet to the susceptibilities of the rare-earth ions which it contains. This enables us to obtain as limiting cases, the results of Kittel, De Gennes, Portis, on one hand, and of Teale and Tweedale, on the other. Then making the slow relaxation hypothesis, we rigorously calculate the susceptibilities of the rare-earth ions and deduce that, in order to be successful, the slow relaxation theory requires that there exist a coupling between the transverse magnetization of the irons, and components of the rare-earth magnetic moments with nonzero diagonal matrix elements. Finally we compare the thermal variations of the ferrimagnetic resonance linewidth and of the relaxation time of the 57Fe nuclei.