bluuebunny/crossref_metadata_2025 huggingface dataset:
Proposed model for bistability in nanowire nonvolatile memory
Authors: Pokalyakin V. , Tereshin S. , Varfolomeev A. , Zaretsky D. , Baranov A. , Banerjee A. , Wang Y. , Ramanathan S. , Bandyopadhyay S.
Published: June 2005

Cadmium sulfide nanowires of 10-nm diameter, electrodeposited in porous anodic alumina films, exhibit an electronic bistability that can be harnessed for nonvolatile memory. The current–voltage characteristics of the wires show two stable conductance states that are well separated (conductances differ by more than four orders of magnitude) and long lived (longevity>1yr at room temperature). These two states can encode binary bits 0 and 1. It is possible to switch between them by varying the voltage across the wires, thus “writing” data. Transport behavior of this system has been investigated at different temperatures in an effort to understand the origin of bistability, and a model is presented to explain the observed features. Based on this model, we estimate that about 40 trapped electrons per nanowire are responsible for the bistability.
Nonlinear electrical characteristics of SnO2∙CuO ceramics with different donors
Authors: Wang Chun-Ming , Wang Jin-Feng , Wang Chun-Lei , Chen Hong-Cun , Su Wen-Bin , Zang Guo-Zhong , Qi Peng
Published: June 2005

The effects of various donors such as Nb, Sb, Ta, and V on the densification and nonlinear current-density J–electrical-field E relations of tin oxide ceramics are investigated. The room-temperature resistivity ρ and the three vital varistor parameters, the nonlinear coefficient α, breakdown electrical field EB, and leakage current density JL, are studied as a function of donor concentration. Minor donors make highly resistive SnO2∙CuO ceramics nonlinear or conductive. The optimum doping samples with tantalum or niobium show promising properties for high-voltage varistor application.
Proteins and polymers
Authors: Banavar Jayanth R. , Hoang Trinh Xuan , Maritan Amos
Published: June 2005

Proteins, chain molecules of amino acids, behave in ways which are similar to each other yet quite distinct from standard compact polymers. We demonstrate that the Flory theorem, derived for polymer melts, holds for compact protein native state structures and is not incompatible with the existence of structured building blocks such as α helices and β strands. We present a discussion on how the notion of the thickness of a polymer chain, besides being useful in describing a chain molecule in the continuum limit, plays a vital role in interpolating between conventional polymer physics and the phase of matter associated with protein structures.
Studies of the interfacial structure of LaAlO3 thin films on silicon by x-ray reflectivity and angle-resolved x-ray photoelectron spectroscopy
Authors: Li X. L. , Xiang W. F. , Lu H. B. , Mai Z. H.
Published: June 2005

The microstructures of amorphous LaAlO3 thin films deposited on silicon substrates by the laser molecular-beam epitaxy were studied by the x-ray reflectivity and the angle-resolved x-ray photoelectron spectroscopy. It was shown that the film∕substrate interface contains a La-rich LaxAlyOzSi layer and a SiOx layer. It was shown that the electron density of the LaAlO3 layer and the LaxAlyOzSi layer is not homogeneous along the growth direction due to the diffusion of La, Al, and Si. The growth kinetics of the LaAlO3 film was described by three processes: (1) formation of the SiOx layer at the early stage whose thickness saturates rapidly at about 13Å; (2) formation of the LaxAlyOzSi layer by the out diffusion of Si and the inner diffusion of La, Al (mostly La). This stage continues as the film grows (3) In the deposition process of LaAlO3, the distributions of La and Al in the LaAlO3 layer change from inhomogeneous to homogeneous.
Wall thickness effect on the resistive wall mode stability in toroidal plasmas
Authors: Zheng L.-J. , Kotschenreuther M. T.
Published: June 2005

The effect of finite wall thickness on the stability of n=1 resistive wall modes in toroidal plasmas is investigated. A fusion reactor-relevant configuration is examined. The investigation employs a novel ideal-magnetohydrodynamics adaptive shooting code for axisymmetric plasmas, extended to take into account the wall thickness. Although finite wall thickness generally reduces the growth rate of the resistive wall modes, no contribution to stabilization is found to be made by the portion of the wall that is located beyond the critical position for perfectly conducting wall stabilization. Thus, when the inner side of the wall lies near the critical wall position, the scaling of the growth rate versus wall thickness in the realistic thick-wall calculation is significantly different from that of the usual thin-wall theory. The thin-wall estimate is relevant only when the wall is brought very close to the plasma and is not too thick.
Noise subtraction in antiferromagnetically coupled magnetic recording media
Authors: Moser Andreas , Supper Natacha F. , Berger Andreas , Margulies David T. , Fullerton Eric E.
Published: June 2005

We have investigated, both experimentally and theoretically, the media noise of antiferromagnetically coupled (AFC) recording media. In particular, we have studied how the lower-layer magnetic properties affect the media noise of the composite system. We find that AFC media perform well even for intrinsically noisy lower layers, such as soft-magnetic Co or CoCr layers with high intergranular exchange coupling. To understand the experimentally observed behavior, we propose a new concept of noise subtraction in AFC magnetic systems, in which the noise of the lower layer is anticorrelated to and subtracts from the noise in the upper layers and acts as a low-pass magnetic filter of the magnetization state in the upper layer.
Isolation effect in ferromagnetic-metal/semiconductor hybrid optical waveguide
Authors: Zayets V. , Ando K.
Published: June 2005

The isolation effect in a ferromagnetic-metal/semiconductor hybrid optical waveguide was experimentally studied. Optical transmission in a Ga1−xAlxAs waveguide covered by Co was found to depend on the magnetization of the Co. The isolation direction was different for a waveguide with a SiO2 buffer layer and for a waveguide with a Ga1−xAlxAs buffer layer used between the waveguide core layer and Co layer. The physical origin of the isolation in this isolator structure was clarified.
Fine-structure N-polarity InN∕InGaN multiple quantum wells grown on GaN underlayer by molecular-beam epitaxy
Authors: Che Song-Bek , Terashima Wataru , Ishitani Yoshihiro , Yoshikawa Akihiko , Matsuda Takeyoshi , Ishii Hirotatsu , Yoshida Seikoh
Published: June 2005

We have succeeded in the growth of very-fine-structure InN∕InGaN (3–16nm∕9nm) multi-quantum wells (MQWs) on GaN underlayer and characterized them by transmission electron microscopy (TEM), high-resolution x-ray diffraction (XRD), and photoluminescence (PL) at 13K. Clear satellite diffraction peaks and sharp heterointerfaces were observed by XRD and TEM, respectively. A single PL-emission peak at 1.75μm was observed in the ten-periods InN(16.1nm)∕In0.67Ga0.33N(9.2nm) MQWs. The use of the InGaN as a barrier layer instead of GaN resulted in remarkable reduction of lattice mismatch between the well and barrier, which was essential for the fabrication of MQWs with superior interface quality. This successful growth of fine-structure InN∕InGaN MQWs would be an important step for the application of InN in optical communication devices.
Relations between Superconductors and Ferromagnets
Authors: Matthias Bernd
Published: June 2005

Ferromagnetic interactions of the rare earth elements in dilute solutions or in compounds with non-magnetic elements have been discovered and will be described. The Curie points are essentially proportional to the spin while the saturation moment follows the value for the effective moment. This ferromagneticinteraction, known to take place via the conduction electrons, follows criteria resembling closely those for the occurrence of superconductivity.

It is shown that by suitable combination of similar superconductors and ferromagnets both phenomena can happen simultaneously in the same crystal.
On the Laws of Magnetization of Ferromagnetic Single Crystals and Polycrystals. Application to Uniaxial Compounds
Authors: Néel L. , Pauthenet R. , Rimet G. , Giron V. S.
Published: June 2005

One of the authors (L.N.) describes the mechanism of magnetization of a ferromagnetic single crystal:the elementary domains can be classified in several groups, called “phases” each having a certain direction of the spontaneous magnetization. The variation of the total magnetization takes place in various “modes,”corresponding to the number of coexisting phases in a given field. The calculation of the magnetization curve in these various modes explains the experimental results for single crystals of iron, pyrrhotine and magnetoplumbite.

The results of measurements at room temperature on this latter compound, 6Fe2O3-PbO, are treated in greater detail. The crystal is uniaxial; for different angles of the external field with the c axis, the magnetization first increases proportionally to the field, followed by a gradual approach to saturation (except for the angles 0 and 90°). The anisotropy constant K1 is first determined (K2 is negligible). The two parts of the curve can be interpreted by two “modes,” with respectively, two and one “phases.”

The variation of the magnetization of polycrystalline 6Fe2O3-BaO samples can be explained by the rotation mechanism only; the crystallites are too small in size to be divided into phases. The experimental curves can be explained by taking into account the interactions between crystallites in calculating the law of approach to saturation.
Harmonic Generation in a Ferrimagnetic Disk
Authors: Bennett Glenn E.
Published: June 2005

A small ferrimagnetic ellipsoid biased to resonance with an arbitrarily directed dc magnetic field will,in general, produce second harmonic components of the magnetization vector in both longitudinal and transverse planes—defined relative to the internal dc field. For an ellipsoid of revolution this paper reports the theoretical dependence upon the direction of magnetization of these and higher harmonic components.

S-band doubling experiments performed on a thin polycrystalline YIG disk mounted in rectangular waveguide confirm the theoretical dependence of the two doubling processes and the expected linear dependence of conversion efficiency on input power. Transverse third and fourth harmonics which were respectively cubic and quartic functions of the input power have also been detected.
Magnetic Anisotropy from the Magnetostatic Modes
Authors: Solt I. H. , Fletcher P. C.
Published: June 2005

The differential equations for the magnetostatic modes in ferrimagnetic resonance have been rederived including the anisotropy torques. Exact solutions have been obtained for four of the low order modes of a sphere. These solutions differ in general from those for the differential equations not including anisotropy. Excellent agreement was found between measured resonance fields and those predicted by the modified theory.
Spin Waves in Complex Exchange-Coupled Lattices and Neutron Scattering
Authors: Sáenz A. W.
Published: June 2005

A spin-wave theory of Holstein-Primakoff type is developed for exchange-coupled lattices with an arbitrary number n of magnetic ions per primitive magnetic unit cell. This theory is used to obtain a cross-section formula for the one-magnon zero-phonon scattering of arbitrarily polarized neutrons by such lattices for the case of complete orbital quenching of the magnetic ions thereof. For n > 1, this equation can be reduced to a simple approximate form in a limiting case, of interest fror certain ferrimagnets, which involves only the scattering of “acoustic” magnons of sufficiently large wavelengths. The parallelism between this last result and the specialization of the above cross section formula for simple ferromagnets (n = 1) is pointed out.
Operation of Magnetic Film Parametrons in the 100- to 500-Mc Regions
Authors: Pohm A. V. , Read A. A. , Stewart R. M. , Schauer R. F.
Published: June 2005

An analysis of the behavior of thin magnetic films of Permalloy when used as time variable inductors has been made in terms of a modified Landau-Lifshitz equation. These results show that parametrons using time variable magnetic film inductors can be made to operate at reasonable power levels with large grains per cycle at oscillating frequencies in the 100- to 500-Mc region.

A way of fabricating magnetic film parametrons with strip line techniques is shown. Calculations indicate that units with dissipations in the 10 mw range are feasible with existing techniques for operation in the 100- to 500-Mc region.

Ways of advantageously using capacitive coupling between parametron units is indicated in which the two new subharmonic states of a magnetic film parametron created by a bias reversel are used.
Ferrite Films—New Logic and Storage Devices
Authors: Brownlow J. M. , Shevel W. L. , Gutwin O. A.
Published: June 2005

Magnetic devices for storage and switching applications in digital computers have been fabricated in the form of open flux path elements. The geometry employed is that of a planar film with thicknesses in the range of 5 to 50 μ and other dimensions in the fractional inch range. These elements have the advantages of a ferrite composition and of open flux paths without many of the disadvantages present in similar metallic devices. For use in storage systems, these devices possess excellent squareness characteristics and have coincident selection times comparable with ferrite-toroidal devices. Properties of these devices are given in terms of switching curves, low-frequency hysteresis loops, and one to zero-signal ratios. Other aspects that are discussed include disturb sensitivity of storage elements,heating effects due to high pulse repetition frequency, and mechanical properties. For each of these, comparison is made with other types of magnetic elements such as toroids and metallic films. Applications are discussed in terms of drive requirements, packing densities, and switching times.
New Approach to High-Speed Storage—Low Flux Density Materials
Authors: Shevel W. L. , Chang H.
Published: June 2005

This paper presents a new approach toward overcoming the factors currently limiting the frequencies at which storage devices may be switched from one information state to another. Ferrite elements for random access storage have been developed which require a fraction of a microsecond for a cycle. Thus the ferrite switching time establishes a maximum switching rate given by the inverse of the total switching time in a cycle. However, operation of elements such as these in a large capacity memory at rates limited only by switching times is usually prevented by:deterioration of magnetic properties due to heating effects, increase in selection line impedance, and long transmission delays.

A series of ferrimagnetic oxides have been developed with properties such that the limits on minimum cycle time are appreciably extended. The most important of these properties is the saturation flux density. Over a range of composition, flux densities have been obtained which extend from 100–500 gauss. The lower flux density results in an appreciably lower energy dissipation in the magnetic structure and consequently in higher switching rates for a given temperature rise within the magnetic material. In addition, temperature dependence of those magnetic properties which determine storage applicability is more favorable than with the better known ferrites.

Toroids have been fabricated with these materials which are suitable for random access memories. These elements have been operated successfully in free air at repetition frequencies in excess of 2 Mc.

The improvements in array characteristics that result are discussed in terms of impedances and transmission delays.
New Multi-Aperture Magnetic Logic Element
Authors: Bennion David R.
Published: June 2005

A new magnetic multi-aperture device (MAD) having general logic capability has been designed, constructed,and tested. This device can be used for either direct or complementary transfer of binary information,depending only on a simple change in wiring. And and or logic functions can be performed in the interconnecting circuitry, which consists only of conducting wire. Significant operating tolerances have been exhibited by the new element, which is simpler in structure and associated wiring than previous MADs having the same logic capability.
Anisotropy Properties of Hexagonal Ferrimagnetic Oxides
Authors: Smit J. , Lotgering F. K. , Enz U.
Published: June 2005

The effects of the incomplete alignment of all magnetic moments of a sample in an applied field on the torque curves are discussed. Examples are given of torque curves determined for cobalt-substituted hexagonal compounds of the ferroxdure type with low anisotropy. It is shown that the characteristic details of these curves can be interpreted in terms of this incomplete alignment, both on a microscopic and an atomic scale.
Exchange Anisotropy in Cu-Mn and Ag-Mn Alloys
Authors: Kouvel J. S.
Published: June 2005

Cu-Mn and Ag-Mn alloy specimens of about 25 atomic % Mn were cooled to 4.2°K in a magnetic field,and it was found that their hysteresis loops measured parallel to this field were displaced from their symmetrical positions about the origin. The displacement of the loops decreases monotonically with increasing temperature, and its disappearance is accompanied by large hysteresis losses. These unusual properties are similar to those previously reported for disordered Ni-Mn alloys and are also attributed to exchange anisotropy interactions between small regions of ferromangetic and antiferromagnetic order. It is proposed that these regions arise from statistical composition fluctuations in the alloys and the existence of both ferromagnetic and antiferromagnetic interactions between Mn atoms. The essence of this microscopic exchange anisotropy model is illustrated for a square lattice representation of these alloys. The magnetic transformation temperatures are identified with anomalies in the 1/χ vs T curves; these temperatures are considerably higher than those at which the exchange anisotropy effects disappear.
Roll Magnetic Anisotropy of Iron-Aluminum Crystals
Authors: Chikazumi Soshin
Published: June 2005

Magnetic anisotropy measurements and domain pattern observations were made on the rolled Fe3Alsingle crystals. Rolling parallel to [001] on a (110) plane induced a uniaxial anisotropy as large as 7.1×105 erg/cc at 12% roll-reduction. The direction of easy magnetization was parallel to the roll direction. Calculations were made on the roll magnetic anisotropy in terms of the “slip-induced directional order model,”under the assumption of (110) (111) slip system. (110) [11̄0], (001) [010], and (001) [110] rollings were also investigated.
Tetrahedral Junction
Authors: Weiss Jerald A.
Published: June 2005

The term tetrahedral junction refers to a class of waveguide junctions having the symmetry properties of a tetrahedron, and loaded by a ferrite rod magnetized axially. The structure possesses a combination of properties which make it suitable as a gyrator or switch and, with appropriate modifications, as an isolator or circulator. It exhibits characteristically low dissipative loss, high mechanical symmetry, and moderate band width. A first attempt to construct a simple theoretical model has yielded a correlation with the most conspicuous observed properties of the junction.
Broadband Reciprocal Ferrite Phase Shifters
Authors: Geiszler T. D. , Henschke R. A.
Published: June 2005

Broadband ferrite phase shifters were constructed in X band waveguide by locating wide ferrite slabs along the center line of the broad waveguide wall and applying a longitudinal magnetic field. The bandwidth of these phase shifters was optimized through proper selection of ferrite dimensions and the amount of dielectric loading or by an appropriate choice of guiding structure. The relative phase shift obtained from broadband configurations was found to vary in an almost linear fashion with the applied field when the ferrite was magnetically saturated.
Multimode Propagation in Gyromagnetic Rods and Its Application to Traveling-Wave Devices
Authors: Tompkins J. E. , Reggia F. , Joseph L.
Published: June 2005

This paper summarizes the results of exact calculations of the propagation constants in longitudinally-magnetized gyromagnetic rods. Specifically described are: (a) the mode behavior for a lossless rod in cylindrical waveguide as a function of rod diameter in the low-field region, (b) a comparison of the calculations with experimental results obtained with a magnetized ferrite rod in rectangular waveguide showing probable negative circular polarization of the field when concentrated within the rod, (c) a brief summary of the calculations of the propagation in rods at high dc fields, and (d) a new broadband microwave absorption switch having constant electrical characteristics over a bandwidth of 3000 Mc at X band.
Rictometer System for Calibrating Transmitters of Remote Indicating Compasses
Authors: Mendelsohn L. I.
Published: June 2005

Calibration of the sensor (transmitter), of a remote indicating compass system, must be carried out in a magnetic field whose magnitude and direction simulate closely those of the earth at a specified point. Major disturbances of the earth's magnetic field by electrical equipment occur in most laboratories. Where conventional Helmholtz calibrating schemes are used, accuracy can be achieved only by lengthy averaging of repeated measurements and exercising extreme care. This paper describes a measurement system called a rictometer, which permits precise transmitter calibration with much greater ease than previously.

The rictometer consists of a system of shields which reduces the earth's horizontal field component from 200 milligauss to about 13 of a milligauss. Two pairs of Helmholtz coils within the shielding system restore the horizontal component of the earth's field. By proper selection of currents in each of these pairs of coils,this horizontal component can be rotated in discrete steps through 360° for calibration purposes. The rictometer allows the experimenter to calibrate a compass transmitter readily with a precision of plus or minus 0.1 deg in normal laboratory fields. Deliberate immersion of the rictometer in a 50 gauss field causes a maximum transmitter calibration change of plus or minus 0.15°. Thus, the system should prove valuable for reliable sensor calibration under most adverse field conditions.
Simple Recording Torque Magnetometer
Authors: Neurath P. W.
Published: June 2005

A recording torque magnetometer has been designed and constructed, using commercially available components in conjunction with commonly available laboratory equipment. It appears to be much simpler than any described heretofore and needs no calibration. The sample disk is mounted at the end of a shaft which is supported in two fixed radial nonmagnetic precision ball bearings of low starting torque. The other end of the shaft carries a 10-cm long lever arm which exerts a force on a Statham Instruments, Inc., 0.3 oz transducer (Model G7A).

The relative rotation of sample to magnet is converted to an electrical signal of any convenient magnitude by use of a 360° continuous rotation Helipot potentiometer. Both torque and rotation signals are recorded on an XY-mv recorder. The electrical circuits consist only of batteries and resistors and the factory supplied transducer calibration is entirely adequate. The assembly can be rotated manually. At ±40 × 103 ergs full scale, corresponding to an output of ±5 mv, errors are about 1%.

Slight alterations in the design to cover full scale ranges from 10 × 103 to 100 × 103 ergs or more are possible.
Effect of Geometry on Thick Film Toroids
Authors: Sagnis James C. , Teig Michael , Ward Robert L.
Published: June 2005

In the study of thick-film magnetic circuits, it has been found that thick film cores of certain sizes could not be completely switched if a concentrated drive winding was used. In addition, the induced voltages differed in waveshape as a function of the location of the sense windings with respect to the concentrated drive winding. Both phenomena were obviously detrimental to the “normal” operation of the device as a magnetic storage or logical element. Studies of these phenomena were conducted using planar thick film toroids, photo-etched from 14-mil and 12-mil thick Square Loop Hy-Mu 80. From the results of these studies, qualitative explanation of the aforementioned phenomena is offered in the form of a three part flux pattern model.
Initial-Permeability Spectra of Microscopic Iron-Oxide Particles
Authors: Brown W. F. , Hanton J. P. , Morrish A. H.
Published: June 2005

The magnetic resonance of single-domain ferromagnetic particles in zero applied steady magnetic field is studied theoretically and experimentally. The axial ratio of the powder particles deduced from the resonance measurements agrees reasonably well with optical data. This is strong evidence regarding the origin of the observed resonance.
The Role of Cation Vacancy in Magnetic Annealing of Iron-Cobalt Ferrites
Authors: Iida Shūichi
Published: June 2005

The kinetics of magnetic annealing effects in iron-cobalt ferritesis studied, based on a vacancy migration mechanism. First, a formal theory is developed, which makes clear the existence of a distribution of relaxation times in the phenomena. In order to get the distribution function of the relaxation time as a function of vacancy concentration and diffusion constants, a calculation based on a rather stochastic approach has been given. It is assumed that the dispersion in the relaxation time comes principally from the time required for the vacancies to migrate throughout the entire crystal lattice. The distribution function obtained is f(τ) = Wρτ/τ0×exp(−Wρτ/τ0),where ρ is the density of vacancies, τ0 is the mean relaxation time for the migration of a single vacancy, and W is a constant which depends on the lattice type, degree of short range ordering, and so on. On using this function the formation and the annihilation of the degree of directionality Su is expressed as ΔSu = ∫0∞f(τ)ΔS(τ)d(logτ), ΔS(τ) = [S(τ)−Se(T)](−Δt/τ0).

A quantitative calculation of the annihilation process of the magnetic annealing anisotropy in isothermal annealing accords exactly with the experimental results for iron-cobalt ferrites.

There is a short discussion of the equilibrium density of vacanciesin iron-cobalt ferrites using the results of our statistical thermodynamical study of the same system. Discussions of several theoretical and experimental results of iron-cobalt ferrites recently carried out in Japan are also presented. From our results we conclude that the decrease in the degree of oxidation simply makes the scale of the time constant of the relaxation process longer, therefore it is not consistent with the suggestion previously made that only cobalt ions near vacancies can rearrange rapidly.
Time Decrease of Initial Permeability in MnxFe3−xO4+y
Authors: Crapo W. A.
Published: June 2005

The time decrease of initial permeability has been measured for several stoichiometric and nonstoichiometric compositions of MnxFe3−xO4+y. The samples were in the form of polycrystalline toroids with compositions x =0.5, 0.7, 0.85, and 0.9. The stoichiometric compositions, y = 0, were fired to maintain a metaloxygen ratio of 3:4, while the nonstoichiometric samples were fired to produce the maximum vacancy concentration. The permeabilities were measured at a peak driving field of 0.002 oe in the temperature range −15° to +35°C. The time decrease data was described by three relaxation times. Activation energies calculated on the basis of these relaxation times were within experimental error equal and independent of the Mn/Fe ratio, i.e., Q = 0.46±0.06 ev. The activation energy for the nonstoichiometric samples was equal to that observed for the stoichiometric samples. The magnitude of the effect in the stoichiometric samples was found to decrease approximately linearly with the increasing Mn/Fe ratio.
Ferroelectric and Ferrimagnetic Properties of (Ba6−2xR2x) (Nb9−xFe1+x)O30
Authors: Fang P. H. , Roth R. S.
Published: June 2005

Materials which possess properties, which strongly suggest both ferroelectricity and ferrimagnetism, are found in the systems (Ba6−2xR2x) (Nb9−xFe1+x)O30 where R is a trivalent rare earth ion and x can vary from 0 to 1. X-ray diffraction powder patterns indicate a single phase having the potassium tungsten bronze type structure also exhibited by Ba6Nb8Zr2O30. When R is Gd+3 and x is at a maximum for this system, the material appears to be both ferroelectric and ferrimagnetic at room temperature. The ferrimagnetism is indicated by the appearance of a remnant polarization and the ferroelectricity by the presence of a dielectric hysteresis loop. The magnetic susceptibility is of the order of 120 at room temperature and exhibits dispersion at frequencies near 20 Mc. Other properties of materials in these systems will also be discussed.
Millimicrosecond Magnetization Reversal in Thin Magnetic Films
Authors: Dietrich W. , Proebster W. E.
Published: June 2005

A special pulse equipment including a pulse sampling oscilloscope with an overall response time of 0.35 mμsec for the observation of the millimicrosecond flux reversal in thin permalloy films is described. Output signals as short as 1 mμsec have been obtained and are discussed with respect to the underlying reversal processes. Inverse switching times versus driving field curves have slopes of about 108/oe sec. Coherent rotation and oscillation of the magnetization have been clearly detected by picking up the flux change transverse to the driving field.
Magnetization Reversal in Uniaxial Films near to the Preferred Direction
Authors: Bradley E. M. , Prutton M.
Published: June 2005

It is now well known that uniaxial thin magnetic films can be made which have almost ideal square hysteresis loops in the preferred direction and almost straight line hysteresis loops in the hard direction. For this type of film, which can be prepared by evaporation from ingots of approximately 81:19 NiFe alloy, it is found that the switching time constant of the reversal process which occurs when magnetic fields are applied exactly in the easy direction can be very large.

The switching process occurring when fields are applied at angle 10° to the preferred direction has been studied in detail, both by a new pulse response technique and by observation of the domain structure revealed by use of the Kerr magneto-optic effect.

In the latter experiment, short pulses have been applied to the specimen and photographs taken of the domain pattern after each pulse. It was found that the specimen breaks into small domains whose area increases after each pulse and that eventually the filmcould be completely reversed if the pulse amplitude was between certain critical values. Curves were plotted of the pulse amplitude against the proportion of the film switched found by measuring the reversed area in the photographs. It was shown that the process is very well approximated by an equation of the form Sw = τ(H − H0),which implies a viscous damped process, and there is a critical nucleation field, which is less than the field required to move the walls.

In the pulse response experiments, the switching time has been derived from the response to a reset pulse which was applied after a variable number of set pulses of variable amplitude. It was found that in some films there can be a rapid switching process, which is complete after about 100 mμsec, followed by a slow process lasting up to 10 μsec under the same conditions. From the experiments performed, it has been possible to compute a switching time constant which can be very large in some films. This constant is found to be correlated with the ratio p = Hc/Hk, where Hc is the coercivity in the easy direction and Hk is the rotational coercivity. If the film obeyed the simple coherent rotational model the pratio would be 1, and films which have p = 0.9 have been found have Sw = 0.3×10−6 oe μsec, whereas for p = 0.3, Sw = 7×10−6 oe μsec.
Microcalorimetric Technique for the Study of Damping and Hysteresis in Ferromagnetic Films
Authors: Mayfield J. R.
Published: June 2005

Experience with experimental techniques for the study of damping and hysteresis in thin films has suggested that many of the difficulties and complications encountered might be avoided by the direct approach of measuring the heat generated by the irreversible processes which are of interest. This suggestion has led to the development of a simple and reliable microcalorimetric apparatus with which accurate loss determinations may be made over a frequency range of about 100 cps to 100 Mc.

The loss detector employed is a thin-film thermocouple which developes an emf proportional to the total heat flux emerging from the ferromagnetic sample. The zero drift of the heat-detecting system is eliminated,and the overall noise level greatly reduced by imposing a low-frequency square-wave modulation on the magnetic losses, amplifying the resultant ac component of the thermal emf with a narrow-band amplifier,and rectifying the output by means of a commutator phase-synchronized with the modulator. It appears that losses as small as 106 erg/sec per cc of sample volume are readily detectable. The thermal method thus has a degree of sensitivity which compares favorably with that of other experimental techniques, and has the added advantage of providing a direct measure of energy loss.
Long-Range Magnetic Interactions via Conduction Electrons
Authors: Paskin Arthur
Published: June 2005

Yosida has shown that the long-range ferromagnetic term arising from the exchange interaction between conduction electrons and unfilled inner-shell electrons, does not appear explicitly when the calculation is extended to second-order perturbation (i.e. the magnetic interaction term to second-order perturbation is not long-range but decreases rapidly with distance). Upon re-examining the Yosida calculation, we find that the long-range magnetic term disappears because of noninteracting electron approximations made for the energy and density of states of the conduction electrons. Without the latter approximation but still to second-order,the long-range magnetic interaction appears with a coefficient proportional to [(∂2E/∂n2)−1−ρ(Ef)]where ρ(Efrpar; is the density of states evaluated at the Fermi energy; n, the number of conduction electrons(of a given spin); and E, their energy. This coefficient can be estimated both from theoretical calculations of Pines on electron interaction effects in metals as well as from nuclear magnetic resonance data. From the calculations of Pines, we conclude that the coefficient is such that the long-range magnetic interaction may not be neglected. On using nuclear magnetic resonance data, we estimate that the magnitude of the long-range term and the short-range interaction term are the same for the Cu-Mn alloys studied by Yosida.
Neutron Diffraction Investigations of the Magnetic Ordering in Rare Earth Nitrides
Authors: Wilkinson M. K. , Child H. R. , Cable J. W. , Wollan E. O. , Koehler W. C.
Published: June 2005

Neutron diffraction investigations on HoN and TbN at low temperatures show that both compounds become ferromagnetic with Curie temperatures of about 18°K and 43°K, respectively. Although the paramagnetic scattering is consistent with moment values calculated for the free trivalent rare earth ions, the observed ferromagnetic moments are lower than the calculated values and indicate the effect of crystalline field interactions. Diffraction patterns from both compounds at 1.3°K show considerable ferromagneticshort-range-order scattering with characteristics which are different from those associated with critical magnetic scattering.
Magnetic-Form Factor of Fe3Al
Authors: Pickart S. J. , Nathans R.
Published: June 2005

A polarized neutron study carried out on the high angle superlattice reflections of ordered Fe3Al shows that the near neighbor environment influences not only the average moment per Fe atom, but also the spatial symmetry of the d electron charge distribution. Preliminary analysis of the form factor indicates that the magnetic electrons of the Fe atom surrounded by 8 Fe near neighbors (which has a moment μ = 2.1μB)preferentially occupy the doubly degenerate eg orbitals, while those of the Fe atom with 4 Fe and 4 Al near neighbors (μ = 1.5μB) favor the triply degenerate t2g orbitals.
Effect of Crystalline Fields on Magnetic-Form Factors
Authors: Freeman A. J. , Watson R. E.
Published: June 2005

The effects of crystalline fields on magnetic-form factors are discussed on the basis of recent Hartree-Fock calculations of Watson augmented by an analysis of experimental optical absorption data. It is shown that the crystalline field has two effects on the free ion 3d wave functions and hence on their form factors as well:(1) a differentiation or “splitting” of the two types of cubic 3d functions by an expansion of the t2g (or eg)orbital and a contraction of the eg (or t2g) orbital resulting in two different radial charge densities and (2) a net expansion of the charge distribution from the free ion value. The magnetic-form factor due to this“splitting” effect when calculated according to the methods of Weiss and Freeman shows measurable deviations from the free atom results. A form factor for Mn+2 based on optical absorption data shows a large expansion of the 3d charge density, in agreement with the measurements of Hastings, Elliott, and Corliss.
Resonance Measurements in Magnetic Garnets
Authors: Rodrigue G. P. , Meyer H. , Jones R. V.
Published: June 2005

The effective g value, anisotropy constants, and line widths of single crystals of YIG, GdIG, SmIG,HoIG, ErIG, and YbIG have been measured over a range of temperatures from 1.5°K to 550°K by ferrimagnetic resonance. The temperature dependence of K1 in both YIG and GdIG is satisfactorily represented by the model of an individual ion subject to a crystalline field in addition to a Weiss molecular field. The g values of HoIG and ErIG appear to be in good agreement with the estimations of Kittel et al. for a ferrimagnetic system with one sublattice strongly damped. It has been found that SmIG and YbIG do not follow the predictions of the Kittel model, since different relative strengths of exchange and relaxation interactions seem to be involved.
Growing Spin Waves in Ferrites in Unstable Equilibrium
Authors: Schaug-Pettersen Tor
Published: June 2005

This paper demonstrates that when the direction of the magnetic field in a saturated ferrite is inverted,spin waves occur which have an aperiodic exponential growth. The fastest growing of these waves have the time factor exp(ΩMt/2) and their wave vector is oriented at right angles to the magnetic field. The significance of these waves for ferrite switching and microwave pulse generation is discussed briefly.
Magnetism in Medicine
Authors: Freeman M. W. , Arrott A. , Watson J. H. L.
Published: June 2005

The applications of magnetic materials and magnetic fields in medicine are reviewed. Direct biological effects of magnetic fields, clinical uses of the mechanical force exerted by magnets, and magnetic analysis as a tool in biochemistry are considered. The authors' applications of the technology of fine particle iron to the treatment of cancer and mental disease, for investigation of basic biochemistry and for diagnostic purposes are discussed. A significant step in these applications has been the discovery of sublingual assimilation of fine particle iron.
Comparison between time-dependent changes in iron metabolism of rats as induced by marginal deficiency of either vitamin A or iron
Authors: Roodenburg Annet J. C. , West Clive E. , Yu Shiguang , Beynen Anton C.
Published: June 2005

To compare the changes in Fe metabolism during the development of vitamin A and Fe deficiencies, rats were given either a control diet with sufficient Fe (35 mg added Fe/kg feed) and retinol (1200 retinol equivalents/kg feed), a diet without added vitamin A or a diet with sufficient vitamin A but only 3.5 mg added Fe/kg feed. During a period of 10 weeks, indicators of vitamin A and Fe status were monitored. Neither vitamin A nor Fe deficiency produced clinical signs. Fe deficiency induced an immediate fall in blood haemoglobin concentration. Vitamin A deficiency produced a mild anaemia as the first change in Fe metabolism, pointing to unpaired erythropoiesis. This effect was followed by a rise in Fe absorption and an increased amount of Fe in the spleen. By the end of the study, blood haemoglobin, packed cell volume, plasma Fe and Fe content in kidney and femur had increased above control levels, while total Fe-binding capacity had decreased. We speculate that the initial anaemia was masked later by haemoconcentration. The decrease in Fe mobilization, shown by lower total Fe-binding capacity, and the increase in Fe absorption may have caused the observed continuous rise in tissue Fe concentration in rats with vitamin A deficiency. In the rats with Fe deficiency, low tissue Fe levels coincided with high Fe absorption and high total Fe-binding capacity. Thus, changes in Fe metabolism with vitamin A deficiency differed from those with Fe deficiency.
Evaluation of fermentability of acid-treated maize husk by rat caecal bacteria in vivo and in vitro
Authors: Hara Hiroshi , Saito Yutaka , Nakashima Hiroshi , Kiriyama Shuh Achi
Published: June 2005

Fermentable energy in insoluble dietary fibre (DF) sources was evaluated byin vivoandin vitromethods using rats. Test diets contained 50 and 100 g maize husk or organic-acid-treated maize husk/kg diet. Soluble fractions were removed from both the DF sources by washing. The acid treatment increased digestibility by a microbial hemicellulase from 12.7% to 32.6%. The fermentabiliry of DF was evaluated by measurement of the production rate of short-chain fatty acids (SCFA) in a short-termin vitroincubation of the caecal contents of rats fed on test diets for 22 d. The production rates of the major SCFA, acetic, propionic and butyric acids, were increased by feeding both DF sources, and these production rates in the acid-treated DF group were significantly higher than those in the untreated DF group. The production rate of a minor SCFA, isovaleric acid, was decreased by feeding both diets. The production rate of total SCFA in rats given the acid-treated maize husk was 32.6% higher than that in rats given the untreated maize husk. The fermentable energy in DF was estimatedin vivoby subtracting the faecal excretion of DF energy from ingested DF energy. The fermentable energy in DF was increased by the acid treatment (32·5% in maize husk and 63.4% in acid-treated maize husk), which agreed with the SCFA production rate predicted in the caecum. These results indicate that a short-term incubation of caecal contents is a useful method for evaluation of the fermentability of DF sources, and that acid treatment can increase the fermentability of an insoluble DF source.
Organizational Socialization: A Field Study into Socialization Success and Rate
Authors: Cooper‐Thomas Helena D. , Anderson Neil
Published: June 2005

The last decade has witnessed a resurgence of organizational socialization research. However, a critical question has been neglected: Is there a common underlying pattern to organizational socialization? We investigated newcomer learning, job satisfaction and intent to quit as common indicators of socialization, in research with 222 newcomers at two organizations during the crucial post‐entry period. The results support a learning‐dependent model of newcomer adjustment, with learning in specific domains related to improved attitudinal outcomes. Some aspects of organizational socialization were not uniform across the two organizations, suggesting a need for further development of socialization models and greater accounting for this in organizational socialization research.
Review article: angiogenesis soluble factors as liver disease markers
Authors: SALCEDO X. , MEDINA J. , SANZ‐CAMENO P. , GARCÍA‐BUEY L. , MARTÍN‐VILCHEZ S. , MORENO‐OTERO R.
Published: June 2005

Angiogenesis is the formation of new blood vessels from pre‐existing ones; it has been studied at the molecular level in different pathologies and is currently considered a promising novel therapeutic target in cancer. Recently, the use of angiogenesis soluble factors as markers of tumour growth has been investigated. The knowledge gained has led to test their use as therapeutic agents. Additionally, angiogenesis soluble factors could be used for the follow‐up of pathologies that currently require monitoring with invasive techniques, like chronic viral hepatitis or renal and haematological diseases. The different factors have been described in multiple studies. In some cases, such as hepatocellular carcinoma, a potential use as prognostic markers has been suggested.
Patients’ and nurses’ perceptions of nursing problems in an acute care setting
Authors: Florin Jan , Ehrenberg Anna , Ehnfors Margareta
Published: June 2005

Aim.  This paper reports a study to determine the degree of agreement or disagreement between nurses and patients in their perceptions of the presence, severity, and importance of nursing problems.

Background.  Patient experiences, values and preferences are increasingly acknowledged as important factors underpinning healthcare decision‐making. The ability to identify patient problems accurately is an important prerequisite for planning and implementing individualized high quality care.

Methods.  A convenience sample of patients (n = 80) and Registered Nurses (n = 30) in an acute care setting responded to a 43‐item questionnaire.

Findings.  Nurses identified patients’ problems with a sensitivity of 0·53 and a positive predictive value of 0·50. Patients identified several severe problems that were not identified by nurses, particularly problems with nutrition, sleep, pain, and emotions/spirituality. Nurses underestimated the severity in 47% of mutually‐identified problems. An overall level of agreement of 44% was found on the importance of patient problems. Low levels of agreement on severity and importance were related more to individual differences than to systematic differences.

Conclusions.  Nurses need to be more aware that patients and nurses often hold disparate views of the priorities in nursing care. To plan individualized nursing care effectively, nurses need to elicit and use individual patients’ preferences more systematically in care planning.