bluuebunny/crossref_metadata_2025 huggingface dataset:
Torque on a spinning superconducting sphere inside a superconducting cylinder or spherical cap
Authors: Holdeman Louis B. , Holdeman Jonas T.
Published: July 2002

A spinning superconducting sphere generates a magnetic field (the London field) while excluding external magnetic fields from its interior (the Meissner effect), so that a torque on the sphere results if there are magnetic or superconducting materials nearby. We calculate the torque on such a sphere inside a concentric, infinitely long superconducting cylinder. We also calculate the torque on such a sphere inside a concentric, spherical superconducting shell in which there is a single circular hole.
Microwave field strength measurement in a rubidium clock cavity via adiabatic rapid passage
Authors: Frueholz R. P. , Camparo J. C.
Published: July 2002

Rubidium atomic frequency standards have been found to display a strong frequency dependence on the microwave power density or field intensity. It is, therefore, desirable to have simple and easily applied techniques for measuring not only the field strength but also the field distribution within the clock’s microwave cavity. A technique which makes use of adiabatic rapid passage (ARP) to measure field strengths in Rb clock cavities is described and demonstrated. Measurements using this technique are found to agree with field strengths extracted using standard microwave procedures. The ARP technique is particularly valuable in cavities where standard microwave measurements cannot be made.
Effects of zinc doping of the antimeltback layer on 1.55-μm InGaAsP/InP lasers
Authors: Feldman R. D. , Hart R. M. , Oron M. , Lum R. M. , Ballman A. A.
Published: July 2002

Broad-area InGaAsP/InP lasers emitting at 1.55 μm have been fabricated from material grown by liquid phase epitaxy. The effects of different levels of zinc doping of the antimeltback layer combined with light doping (≤5×1017 cm−3) of the InP cladding layers have been studied. Threshold current densities of 2.1–2.3 kA cm−2 are found under a range of zinc-doping levels. The quantum efficiencies are highest, approximately 19% per facet, when the antimeltback layer is undoped. With zinc doping, the quantum efficiencies drop by a factor of 2–3. Photoelectrochemical etching has been used to reveal the p-n junction. The etching shows that the zinc doping yields an increase in the small scale variations in the placement and abruptness of the p-n junction.
Self-aligned rib-waveguide large optical cavity AlGaAs laser for high-power single-mode operation
Authors: Shimer J. A. , Holbrook W. R. , Reynolds C. L. , Thompson C. W. , Olsson N. A. , Temkin H.
Published: July 2002

A new self-aligned rib-waveguide structure using a large optical cavity for high-power single-mode operation is presented. cw output powers of 40 mW are achieved with linear light-current (L-I) characteristics and single transverse and longitudinal modes. Over the temperature interval 10 to 60 °C, we find a typical T0 of 270 K. This laser is easily coupled to a single-mode fiber and has been modulated to 2 GHz with only a 3-dB loss in output power.
Ultrasonic diffraction grating using an interdigital transducer operating at a liquid-solid interface
Authors: Urabe Heijiro , Watabe Kohji , Toda Kohji
Published: July 2002

An ultrasonic optical modulator using an interdigital transducer operating at a liquid–solid boundary is described. The fundamental characteristics of the optical modulator are given for a combination of a He–Ne 0.63-μm laser and water as an acousto-optic material. The modulator consists of a piezoelectric ceramic plate with interdigital electrodes. The diffraction pattern can be varied by changing the voltage or the frequency of the electrical signal applied to the transducer. By using the voltage dependence of the first-order diffraction peak, we demonstrate optical modulation.
Gauging film thickness: A comparison of an x-ray diffraction technique with Rutherford backscattering spectrometry
Authors: Coulman Betty , Chen Haydn , Rehn L. E.
Published: July 2002

An x-ray diffraction technique for determining thin-film thickness is presented which should prove to be a valuable alternative to the array of spectroscopies (Rutherford backscattering spectrometry, Auger electron spectroscopy, etc.) currently favored for these measurements. Some of the virtues of this x-ray diffraction approach are its nondestructive nature, fast data acquisition rate (enabling in situ observations), thickness resolution better than 5 nm, and conventional equipment requirements. Results are shown for Pd2Si thin films grown during isothermal annealing of Pd coatings (100 nm) on Si at 200 °C for various amounts of time. A comparison of these x-ray measurements with Rutherford backscattering spectrometry data taken from the same specimens is used to demonstrate the validity of the x-ray technique.
Temperature dependence of the coercive field of SmCo5 at high temperatures
Authors: Searle C. W.
Published: July 2002

The coercive fields of SmCo5 single crystals and sintered permanent magnets are compared with a simple model for the magnetization reversal process. It is found that a consideration of microscopic variations in the exchange energy is required to understand the magnetization reversal at high temperatures.
Chemography of silicon surfaces
Authors: Meieran Eugene S. , Blech Ilan A. , Herman Michael H.
Published: July 2002

Recently, it has been shown that images can be formed in darkness by placing surfaces of silicon or other materials in contact with sensitive photographic films such as Ilford Nuclear Emulsion G5 or L4. These ‘‘chemographic’’ images are observed by developing the emulsion after a suitable period of exposure. The time required for image formation depends upon the nature of the surface to be imaged and the humidity of the exposing environment. Freshly etched or abraded Si surfaces, exposed to films in moist atmospheres, may require only hours of exposure, while heavily oxidized Si surfaces, exposed in drier atmospheres, may require days or weeks to generate chemographic images. These observations are consistent with previous studies which suggest that atomic hydrogen, created during the silicon oxidation process, is responsible for image formation. In this paper, some effects of surface properties on the strength of the chemographic images are discussed. In particular, images of twinned crystals show the dependence of gas evolution on surface orientation, and images of patterned Si show the influence of dopant levels on oxidation rates. Additionally, images of a variety of purchased silicon wafers demonstrate differences between vendors of identically specified material.
Luminescence study of rapid lamp annealing of Si-implanted InP
Authors: Kirillov D. , Merz J. L. , Kalish R. , Shatas S.
Published: July 2002

Luminescence of Si-implanted InP after rapid lamp annealing was studied. It was found that the intensity and energy of band-to-band room-temperature luminescence were good indicators of the quality of annealing and activation of Si donors. Shallow and deep level spectral features characteristic of Si implantation and good annealing were observed in the low-temperature spectra. It was found that the best results could be obtained only in the case of hot implantation and lamp annealing in regimes close to the melting point of the InP, whereas room-temperature implantation and oven annealing were much less effective.
Characteristics of tin and cadmium doping in liquid-phase epitaxial grown InGaAsP
Authors: Tamari N. , Degani J. , Shtrikman H. , Ballman A. A.
Published: July 2002

The characteristics of tin and cadmium doping of liquid-phase epitaxial grown InGaAsP layers have been investigated. A change in the solid composition of the quaternary is introduced as a result of the perturbation of the liquid solution composition by the dopants. This leads to a change in the lattice constant and a shift of the photoluminescence peak wavelength of the doped layers. Impurity band formation and band filling enhance the shift of the peak wavelength towards shorter wavelength in the case of tin doping while it substantially counteracts this shift in the case of cadmium. The critical carrier concentration for obtaining maximum luminescence efficiency was determined for the two dopants and the results are consistent with previously published results on InGaAsP/InP double heterostructure lasers. Unintentionally doped InGaAsP layers have also been examined.
Interpretation of thermoelectric power in silicon-on-sapphire films by means of a long-range potential-fluctuation model
Authors: Dusseau J. M. , Ada-Hanifi M. , Robert J. L.
Published: July 2002

The aim of this paper is to formalize thermoelectric power in terms of a model of long-range fluctuations in potential previously developed in numerous papers. We apply this model to the electrical data on silicon-on-sapphire films taking account of the fact the conduction takes place exclusively in a degenerate transition layer of the film at the Si-Al2O3 interface.
Determination of trapped charge distributions in the dielectric of a metal-oxide-semiconductor structure
Authors: Przewlocki H. M.
Published: July 2002

Charge trapping in the insulator of a metal-oxide-semiconductor (MOS) structure strongly influences photocurrents resulting from electron photoinjection from the gate, or from the semiconductor electrode, into this insulator. This influence may be used to determine trapped charge distributions (profiles) in the dielectric layers of MOS structures. In this paper, several trapped charge profiles are considered, and the influence of these charges on the MOS structure photoelectric characteristics is discussed. Detailed solutions are derived for uniform, step, delta, rectangular, exponential, and Gaussian distributions of electrons trapped in the dielectric of a MOS structure. All these solutions are based on the barrier position mode approximation of the Powell–Berglund formulas. A comparison of experimentally obtained photocurrent-voltage characteristics of a MOS structure (taken both before and after the charge trapping took place) with characteristics calculated using expressions derived in this paper allows approximate determination of the trapped charge profile in this particular sample.
Saturation velocity phenomena in implanted garnet films
Authors: Pintér I. , Bódis L. , Kleparski V. G.
Published: July 2002

The domain wall velocity of ion-implanted garnet films is measured on expanding stripe domains observed—using a laser-flash optical microscope, for wide drive field and temperature range. Comparison of measured and calculated velocities shows the insufficiency of present theories. A simple model is suggested for describing the saturation velocity phenomena in implanted garnet films. This model shows the wall structure distortion at the effective films surfaces to be approximated by a transient Bloch line zone. The average static azimuthal angle is assumed to be ψ̄0=π2Λ0/D in good agreement with the experimentally obtained ψ̄0=11.8 Λ0/D, where D is the effective film thickness and Λ0 is the Bloch line width parameter. The calculated saturation velocities agree surprisingly well with the experimental results for wide thickness and temperature range.
A dual arctangent model of the perpendicular magnetic recording transition
Authors: Koren Norman L.
Published: July 2002

A simple approximately self-consistent model of the perpendicular magnetic recording write process is presented, in which the transition is represented by two arctangents. This model is valid for any type of recording head. It is developed by considering (1) the transition immediately following the write field reversal, and (2) the demagnetization that takes place after the transition region has been removed from the head. Agreement with experiment is greatly improved over simple arctangent models.
Application of Mössbauer techniques to the study of orientation of particles in magnetic recording tapes
Authors: Kitahata S. , Kishimoto M. , Amemiya M.
Published: July 2002

Mössbauer techniques were applied on the two types of tapes, longitudinally and perpendicularly oriented tapes having the coercivity of 300–1500 Oe to evaluate the orientation of particles in tapes. The demagnetizing factor, N, in the perpendicular direction in the tapes was determined by examining the deviation of squareness in the hysteresis curve from the Mössbauer results. In the longitudinally oriented tapes, the squareness agreed with the Mössbauer results by correcting the effect of the demagnetizing field using N=1. In the perpendicularly oriented tapes, the value of N depended on the degree of orientation of particles, and decreased with increasing the degree of orientation of particles in the perpendicular direction.
Theory of magnetostatic-wave delay-line based oscillators (abstract)
Authors: Tuan H. S. , Parekh J. P.
Published: July 2002

Promising experimental results on tunable magnetostatic-wave (MSW) delay-line based oscillators have recently been reported wherein lifted transducers are used for the achievement of delay line narrowbanding and single-mode oscillator operation over a wide tuning range. One of the important theoretical problems in the study of these oscillators is a determination of optimum device performance parameters including the delay-line effective Q factor and the oscillator noise figure. The present paper reports a phenomenological theory of MSW delay-line based oscillators which has been developed from first principles and incorporates the effect of all the elements in the oscillator loop. The theory has yielded an expression for the effective Q of the delay line which interestingly and, indeed, naturally has the same form as the expression of the Q for an open-cavity laser. The paper will discuss qualitative implications of the theory and present quantitative information on the oscillator performance characteristics and their dependence on different parameters.
A theory for pressure dependence of electron paramagnetic resonance zero-field splitting of NiSiF6⋅6H2O
Authors: Xiong Quan , Bai Gui-Ru , Zhao Min-Guang
Published: July 2002

By using the high order perturbation formula of EPR zero-field splitting for d8 configuration in trigonal crystal field proposed by us, and using the approximate SCF d orbit of Ni2+, an interpretation for the pressure dependence of zero-field splitting of NiSiF6⋅6H2O, which has been a still imperfectly understood problem, is given. In addition, the state equation dependent on pressure for NiSiF6⋅6H2O is predicted.
Topography, domain structure, and magnetostriction measurements on Tb0.5Dy0.5Fe2 under stress (abstract)
Authors: Savage H. T. , Clark A. E. , Lord D. L. , McMasters O. D.
Published: July 2002

We have characterized a textured cylindrical sample of Tb0.5Dy0.5Fe2 (54 mm×6 mm diam) by topography and metallography. The topography shows long ( 20 mm) slender grains with a [110] axis along the sample axis. The grain boundaries are less than 1°. Domain walls can be seen by both Berg–Barrett technique and optical observations. This composition has a large anisotropy, Ki=5×106 erg/cm3. We find that under stress the magnetization occurs by ‘‘jumping’’ of the moment from a [111] axis perpendicular to the axis to the [111] direction closest to the axis of the sample. A large hysteresis accompanies this effect. In comparison with samples of other RFe2 (R=rare earth) compositions, the results of the high stress magnetization and magnetostriction experiments show two features: (1) the sample saturates with a much sharper ‘‘knee,’’ and (2) a much higher energy conversion is obtained. We conjecture the difference between this sample and the other RFe2 compounds is its lack of Widmanstatten precipitate, i.e., a much higher sample perfection.
Magnetic excitation in CuMn spin glass alloy
Authors: Tsunoda Y. , Kunitomi N. , Cable J. W.
Published: July 2002

The spin dynamics of a spin glass alloy Cu78.7Mn21.3 have been studied by neutron inelastic scattering. Measurements have been made at 20, 150, and 290 K by the constant E mode of operation. Magnetic excitations with rather large energy transfer have been observed around the (1  1/2  0) and the (1  1/2 ±δ 0) magnetic diffuse peak positions above and below the spin freezing temperature (Tf∼90 K). The results indicate the existence of strong space and time correlations of the spins over the temperature range of the measurements. The experimental data are well explained by a model of dynamically fluctuating spin clusters with a broad distribution of relaxation times.
Neutron diffraction observation of only incommensurate magnetic structures in the series of helimagnets La2FexMn2−xS5
Authors: Plumier R. , Sougi M. , Lecomte M. , Keller-Besrest F.
Published: July 2002

The pitch angles φ of the double helix observed in the series of binary sulfurs La2FexMn2−xS5 (1≤x≤1.8) are studied as a function of x and temperature. At all temperatures, φ increases by about 15% while going from x=1 to x=1.8, whereas, for all compounds, an increase of about 10% is observed while the temperature varies from 5 K to the upper temperature allowing the observation of the magnetic reflections. In a total of 25 experiments, the variations of φ with x and temperature are observed to be smooth.
Temperature and magnetic field effects of the magnetic excitations in Rb2 CoxMg1−xF4 (abstract)
Authors: McGurn A. R.
Published: July 2002

We calculate the neutron scattering from the magnetic excitation in Rb2CoxMg1−xF4 at arbitrary temperatures and in the presence of weak external fields (less than the critical fields). The calculation is made by combining the computer simulation techniques of Alben and Thorpe with Monte Carlo methods used in the study of the finite-temperature Ising model. A comparison with a series of experiments involving various combinations of temperatures, concentrations, and fields is made and excellent agreement between theory and experiment is found.
Neutron-spin depolarization in Y9Co7 and Y9(Co0.97Ni0.03)7 (abstract)
Authors: Sarkissian B. V. B.
Published: July 2002

We have made new measurements of the spin depolarization of neutrons transmitted through the magnetic superconductor Y9Co7 [B. V. B. Sarkissian, J. Appl. Phys. 53, 8070 (1982) and references therein] and the weak magnet Y9(Co0.97Ni0.03)7 [B. V. B. Sarkissian and J. L. Tholence, J. Appl. Phys. 55, 2025 (1984)]. These measurements were carried out on the IN11 spectrometer at Institut Laue-Langevin (I. L. L.), Grenoble, France. These studies were carried out as a function of temperature and magnetic field using polarized neutrons of wavelength 6.4 Å. The result clearly confirms the existence of sharply differing T-dependence depolarization characteristics for a given field. At the lowest fields (∼2 Oe) the data reveal unexpected behavior in both specimens. No depolarization effect or any prominent feature was observed at either transition of Y9Co7, although some depolarization seems to occur below ∼6.5 K in the Ni-doped specimen in a field of ∼2 Oe. This suggests a behavior similar to that which would occur in systems in which the local magnetization is strongly influenced by the temporal fluctuations of a finite lifetime (analogous to quasilocalized magnetic state). This we associate with the ‘‘hopping’’ process of the c-axis Co atoms along the chains which prohibits magnetic ordering [B. V. B. Sarkissian (these proceedings)]. On the other hand, application of higher fields (>2 Oe) seems to produce stronger effects in both samples. A gradual increase in depolarization is apparent with cooling below ∼6 K in Y9Co7 and ∼6.5 K in the Ni-doped specimen. The depolarization becomes more pronounced in both samples with increasing fields. It is notable however, that in these experiments the depolarization is small and never observed to be complete. We note also that at a given field the depolarization in the Ni-doped specimen exceeds that of Y9Co7 by a sizable factor. The features pertaining the depolarization curves in the presence of small external field (>2 Oe) could be associated to the creation of a large local field which can be ascribed to the stiffening of the spin fluctuations by the applied fields. The stiffening also seems to be enlarged by Ni impurities. There is also a very striking reduction in the depolarization below the superconducting transition temperature Ts (∼2.5 K) of the Y9Co7. This effect weakens with increasing the field. In general this result is consistent with the previously reported depolarization data [B. V. B. Sarkissian, J. Appl. Phys. 53, 8070 (1982)] which have also shown the reduction in the neutron depolarization below Ts in a different specimen and under different conditions. This is an intrinsic effect and could be explained by suppression of the spin density.
Recent high-resolution neutron inelastic scattering studies of magnetic systems (invited)
Authors: Stirling W. G.
Published: July 2002

The advent of highly efficient (neutron) cold sources in research reactors has permitted studies of the excitations in condensed matter with improved instrumental resolution and at much lower energies than previously possible. For example, the triple-axis crystal spectrometer on the ILL cold source permits studies with resolutions in the range from (roughly) 1 to 0.02 meV (20 μeV). Even better resolution, extending below 1 μeV, is provided by the neutron-spin-echo spectrometer. In this article, recent work on magnetic systems, at ILL, using high-resolution inelastic scattering techniques, is briefly reviewed. We shall describe a spin-echo investigation of the critical dynamics of iron and then a series of triple-axis measurements of critical scattering and magnetic excitations in a variety of materials, USb, Rb2CrCl4, Pr, Nd, TMMC, CsCoCl3, and, finally, a polarized neutron study of CsNiF3.
Nuclear spin ordering observed by neutron diffraction (invited)
Authors: Nicklow R. M. , Moon R. M. , Kawarazaki S. , Kunitomi N. , Suzuki H. , Ohtsuka T. , Morii Y.
Published: July 2002

A review is given of recent neutron scattering experiments which have been carried out at milli-Kelvin temperatures to study the hyperfine-enhanced nuclear-spin ordering in the singlet electronic ground state compounds PrSn3, PrCu2, and HoVO4. Bragg peaks were observed in PrSn3 which are due solely to the nuclear spin polarization of 141Pr caused by the hyperfine field from the antiferromagnetically ordered electronic moment. The temperature dependencies of the nuclear polarization and the additional electronic polarization induced by the nuclear polarization have been measured in detail. A magnetic phase transition in PrCu2 which is believed to correspond to a simultaneous ordering of both the nuclear and electronic spin systems has been observed at 58 mK. The positions of the magnetic diffraction peaks in reciprocal space are represented by G±τ, where G is a vector of the reciprocal lattice and τ=0.24a*±0.68c*, indicating that the magnetic periodicity is incommensurate with the chemical lattice. In HoVO4 magnetic diffraction peaks due to the antiferromagnetic ordering of the nuclear spin system were observed below 4.5 mK. The observed magnetic structure and the dependence of the neutron diffraction intensities on magnetic field are consistent with the predictions of Bleaney on the basis of dipolar energy considerations.
Properties of rare-earth metal superlattice grown by molecular-beam epitaxy (abstract)
Authors: Kwo J. , Gyorgy E. M. , Hong M. , Lowe W. P. , McWhan D. B. , Superfine R.
Published: July 2002

Metal superlattices are predicted to exhibit novel properties such as zone-folding effects of electronic bands and phonon dispersions. Heterostructures consisting of rare-earth magnetic metals Gd, Tm, and nonmagnetic elements Y, Lu with nearly perfect lattice match provide the unique opportunity of studying on the atomic scale the RKKY interaction, and the resultant magnetic ordering spin phases. However, such study would be fruitful only if the layer modulation direction coincides with the crystallographic C axis and a compositionwise sharp interface is achieved. Furthermore, because of the strong reactiveness of rare-earth metals with gas impurities, these stringent film growth requirements can be best met by molecular-beam-epitaxial technique in a UHV environment. We have grown the rare-earth metal single and multilayer films in a versatile UHV deposition system equipped with effusion cells and e-beam evaporators. The typical growth rate is 1 monolayer/s, and the typical background pressure during growth is 1.0×10−10 Torr. With the in situ RHEED characterization, the preferred film growth direction, namely C axis, is controlled by optimizing the substrate temperature, and growth planes of substrates including sapphire, mica, and single crystal yttrium. Magnetic properties including anisotropy and moments versus temperature are studied by vibrating sample magnetometry on these multilayers with modulation wavelength varying from 20 to 200 Å. Results of x-ray structure analysis, Rutherford backscattering depth profile, and the resistivity measurements will also be reported.
Observation of standing spin waves in thin Fe films by means of Raman spectroscopy
Authors: Blumenröder S. , Zirngiebl E. , Grünberg P. , Güntherodt G.
Published: July 2002

We report on the first observation of standing spin waves in thin evaporated Fe films by means of Raman scattering (RS). In earlier investigations using Brillouin scattering (BS) these modes could only be observed down to a thickness d≊200 Å. We were now able to extend this range down to d≊120 Å using BS and to 40 Å using RS. We find that for values of d comparable to the penetration depth of the light the scattering intensity decreases together with d. This is explained by the assumption that the scattering intensity is determined by the net magnetic moment resulting within the probing depth of the light. The mode frequencies ν observed by RS as a function of d follow very well a ν∼D*exd−2 relationship from which the value of the exchange parameter Dex has been determined.
Microwave transmission through ferromagnetic metal slabs with nonlocal conductivity and specular or diffuse scattering of carriers
Authors: Urquhart K. B. , Cochran J. F.
Published: July 2002

The transmission of circularly polarized microwave radiation through a slab of ferromagnetic metal has been numerically evaluated as a function of an external dc magnetic field oriented normal to the slab faces. The calculation used a nonlocal relationship between the current density at a point in the metal and the electric field distribution in the metal. The two limiting cases of specular and diffuse scattering of the current carriers at the slab faces were investigated. The calculations were carried out for conduction mean free paths l ranging from the anomalous skin effect regime (δ/l<1) to the regime corresponding to the local limit (δ/l≫1). For simplicity, a spherical Fermi surface was assumed whose parameters were chosen to simulate Nickel. The permeability was calculated from the Landau–Lifshitz equations including Gilbert damping and magnetocrystalline anisotropy but ignoring exchange and diffusion. For 24-GHz radiation incident on a 5-μm-thick slab, a mean free path of 1.0 μm, and for diffuse scattering of the carriers, a strong transmission peak appeared when the dc magnetic field was at a value corresponding to ferromagnetic resonance (FMR). No such peak was observed under specular scattering.
Magnetostriction and magnetic core loss at high frequency in amorphous Fe-based alloys
Authors: Inomata K. , Sawa T. , Hasegawa M.
Published: July 2002

Coercive force Hc and core loss at high frequency f up to 100 kHz were investigated for amorphous Fe-based alloys with various magnetostrictions. Log Hc is shown to be proportional to log f. Magnetic core loss at high frequency for annealed toroidal cores of amorphous Fe-based alloys was shown to be significantly dependent on magnetostriction. Core loss and rectangular ratio in a dc B-H loop are influenced by the number of amorphous tape winding turns N, which is interpreted in terms of surface oxidation of the toroidal core. Very low core losses of 195 mW/cm3 and 350 mW/cm3 (3 kG, 50 kHz) were attained for a ring and a toroidal core, respectively, of the amorphous (Fe0.82Ni0.10Nb0.08)83Si5B12 alloy with a low magnetostriction of 5×10−6.
Magnetic relaxation in amorphous (Fe,Co)100−xBx alloys
Authors: Miyazaki T. , Takahashi M. , Hisatake K.
Published: July 2002

The disaccommodation and the uniaxial magnetic anisotropy induced by magnetic annealing were studied for rapidly quenched amorphous Fe100−xBx (12≤x≤25) and Co100−xBx (17≤x≤30) alloys. The disaccommodation exhibits a maximum between 150–250 °C for Fe-B and 50–250 °C for Co-B alloys. The compositional dependence of both disaccommodation and induced magnetic anisotropy constant exhibits an anomaly at x=20. The origin of disaccommodation is discussed in connection with the induced magnetic anisotropy. Further, the compositional dependence of induced magnetic anisotropy is discussed based on the compositional short-range ordering.
Kinetics of the Curie temperature relaxation and anelasticity in amorphous alloys
Authors: Jagielinski T. , Egami T.
Published: July 2002

The kinetics of the Curie temperature relaxation phenomena of amorphous Fe32Ni36Cr14P12B6, including the effect of preannealing, are shown to be well explained in terms of the activation energy spectrum for anelasticity if we assume that an anelastic atomic rearrangement affects the local compositional short-range order of about 10 atoms. This result further supports the view that the kinetics of various reversible relaxation phenomena are determined by anelasticity.
Magnetic properties and microstructure of sputter-deposited Ho-Co amorphous alloy thin films
Authors: Suzuki T. , Aoyagi E. , Ichinose H.
Published: July 2002

A detailed investigation of the structure of Ho19Co81 sputter-deposited amorphous films has been carried out by high resolution transmission electron microscopy. A columnar structure which is amorphous and is well developed along the thickness direction contains microcrystalline regions which provide a clear lattice image in the micrographs. Such microcrystalline regions distribute locally and the structure is very close to that of HoCo5 intermetallic compounds. The change in magnetization in an isothermal annealing experiment in vacuum is also discussed. The activation energy which was deduced from the temperature dependence of the 50% change of magnetization was found to be 0.56 eV.
Dynamics of domain walls in amorphous GdFe ultrathin films
Authors: Bernstein P. , Gueugnon C.
Published: July 2002

The magnetization process of amorphous GdFe ultrathin films with perpendicular anisotropy occur by domains nucleation and domains wall (DW) motion. The DW motion is studied optically as a function of the applied field H at room temperature. It is found experimentally that the DW velocity can be expressed as V =C0 exp (H/H1) where H1 is a linear function of the nucleation field HN which depends on the nature of the alloy. The dependence of the DW velocity on the applied field is assumed to be related to the interaction of DW with pinning centers which can be overcome by thermal activation according to a model given by Riehmann and Nembach [J. Appl. Phys. 55, 1081 (1984)].
Characterization of highly magnetostrictive metallic glass coatings
Authors: Tyagi S. , Larson D. C. , Bobb L. C.
Published: July 2002

Amorphous films of Fe81B13.5Si3.5C2 were prepared by conventional diode rf sputtering with a deposition rate of about 100 Å/min. The films are magnetically harder than the ribbon samples of the same composition. By appropriate magnetic annealing treatment anisotropy energy values in the range of 60–600 J/m3 have been obtained. The effect of thermal and magnetic annealing on various magnetic properties is also discussed. The relevance of the results of this study to the performance of fiber optic magnetic field sensors which utilize such magnetostrictive glasses is discussed.
Studies on glassy ferromagnet Fe67Co18B14Si1
Authors: Bhatnagar A. K. , Prasad B. Bhanu , Jagannathan R.
Published: July 2002

5 7Fe Mössbauer spectroscopy has been used to study magnetic properties, annealing, and crystallization behavior of metallic glass Fe67Co18B14Si1 (Metglas 2605C0). Its crystallization temperature, Tx, is observed to be 650 K. The Curie temperature, estimated from temperature dependence of magnetic hyperfine field, is found to be 830±10 K. Probability distribution of hyperfine fields P(H) shows a single peak of FWHM 91 kOe which decreases with increase in temperature. Effect of annealing at temperatures from 373 to 673 K for 4 to 96 h indicates that the sample gets crystallized at 673 K after heat treating for longer periods (∼12 h), a temperature higher than Tx (650 K) obtained from temperature dependence of Mössbauer spectra indicating dependence of Tx on heat treatment. The ‘‘as received’’ sample when annealed at 673 K for 12 h or more shows the presence of α-(Fe0.7Co0.3) (Fe0.3Co0.7)2B, and (Fe–Co)3B phases. However, the sample used for the temperature dependence of Mössbauer spectra up to 900 K shows the presence of only α-(Fe0.7Co0.3) and (Fe0.3Co0.7)2B, indicating that the thermal history has significant effect on crystallization products.
The effect of Cr on the electrical resistivity of amorphous Fe75P16B6Al3
Authors: Gudmundsson H. , Hannesson H. J. , Åström H. U.
Published: July 2002

The authors have studied electrical resistivity as a function of temperature and magnetic field in the glassy alloy system (Fe1−xCrx)75P16B6Al3 for x=0.05, 0.1, 0.2, and 0.3. A logarithmic rise of different magnitudes is seen in two different temperature regions. The low temperature data can be scaled on a ‘‘universal’’ curve giving monotonic variation of relevant parameters with the concentration of Cr. This suggests magnetic influence on the scattering while the observed (T)1/2 dependence implies effects of electron interaction in disordered metals.
Hyperfine field distribution in amorphous speromagnets (abstract)
Authors: Eibschütz M. , Lines M. E.
Published: July 2002

The 57Fe Mössbauer Zeeman spectra for amorphous ferric speromagnets a-Y3Fe5O12 (YIG) and a-FeF3 consist of well-resolved broad experimental lines, which indicates the existence of a distribution of electric field gradients, hyperfine fields, and isomer shifts at the iron sites. A quantitative analysis of mean line positions, root-mean-square widths, and line shapes of the Mössbauer lines enables us to obtain information concerning the statistical distribution of iron environments in the glassy matrix. The hyperfine field distribution in amorphous speromagnets a-YIG and a-FeF3 is shown to result dominantly from local spin disorder via the supertransferred components HST. Since this same spin disorder determines local exchange fields Hex, the hyperfine field distribution indirectly contains much information concerning the distribution of Hex in the ‘‘spin glass’’ environment. We find, in particular, the mean exchange field 〈Hex〉 is only some 6% of its equivalent in crystalline YIG and FeF3. The hyperfine-field distribution p(H) possesses a small-amplitude low-field ‘‘tail’’ which at 4.2 K contains ∼2% and 5% of the total sites a-YIG and a-FeF3, respectively. A theoretical explanation of the origin and shape of the tail is given, and it is expected to disappear completely in the limit T→0. The limiting shape of p(H) as T→0 is quantitatively established and is significantly asymmetric about its peak.
Magnetic field dependence of the small angle scattering in amorphous DyCu
Authors: Pickart S. J. , Hasanain S. , Andrauskas D. , Alperin H. A. , Spano M. L. , Rhyne J. J.
Published: July 2002

The previously reported small angle neutron scattering (SANS) from the spin glass amorphous DyCu (TF =17 K) was examined in applied fields up to 15 kOe. Application of the field caused a decrease of the total SANS intensity and a decrease of the correlation length derived from the Lorentzian line shapes to ∼6 Å from the zero field value of 13.5 Å. Field-cooling and relaxation effects were also observed in the SANS intensity and are compared with similar phenomena in magnetization measurements.
Quasi-one-dimensional antiferromagnetism in FeC2O4 ⋅ 2H2O
Authors: Chen Jiing-Yann , Simizu Satoru , Friedberg S. A.
Published: July 2002

The magnetic susceptibility χp and heat capacity Cp of α-FeC2O4 ⋅ 2H2O have been measured on powder specimens between 1.2 and 100 K. χp shows a broad, smooth maximum with Tm≂40 K and falls monotonically with temperature. It remains constant below ∼7 K at one-third its maximum value. Cp exhibits a small cooperative peak at 11.7 K which coincides with a pronounced maximum of dχp/dT, indicating antiferromagnetic long-range ordering. These results are explained by a quasi-one-dimensional Heisenberg antiferromagnetic model with S=2 spins which is consistent with the oxalate-bridged Fe2+ ion chains in α-FeC2O4 ⋅ 2H2O. Ising models were employed to explain the dispersion of experimental and theoretical χp curves below Tm.
Spatial and dynamic spin correlation of C
uMn (5 at. %) spin glass: Inelastic neutron scattering study
Authors: Uemura Y. J. , Shapiro S. M. , Wenger L. E.
Published: July 2002

Neutron scattering experiments have been performed on a spin-glass CuMn (5 at. %, Tg =27.6 K). Polarized neutron measurements with coarse energy resolution show no change of instantaneous spatial spin correlation below T=60 K. Unpolarized neutron studies with fine energy resolution (ΔE=260 μeV) demonstrate that the slowing down of Mn spin fluctuations occur in the same way for all the wave vectors between 0.2 and 4.0 Å−1. These results indicate that the spatial and dynamic spin correlations are completely decoupled in the spin freezing process. We also study the short-range spatial correlation of the ‘‘frozen’’ spins at T=5 K using a simple model, and demonstrate the importance of the ferromagnetic coupling between the third nearest-neighbor Mn moments.
Magnetic ordering and crystal-field effects in the Ce deuterides (abstract)
Authors: Arons R. R. , Heidel Angelika , De Boer F. R.
Published: July 2002

In contrast to the heavier RE dideuterides, which exist only in a narrow region around D/RE≊2, the fcc Ce deuteride forms a large region of homogeneity ranging from D/Ce equal to 1.95 up to about 3.0. A metal-to-semiconductor transition occurs for D/Ce above about 2.7. Therefore, this system is ideal for investigating the influence of the conduction electrons on the magnetic order. Recently, it was shown by us that CeD1.95 orders antiferromagnetically (AF) below TN =6.2 K. Due to the occupation of the octahedral sites for D/Ce above 1.95, this order was found to decrease to below 1 K for CeD2.00. In the present work, the magnetic susceptibility has been measured for D/Ce ratios near its saturation value of 3. It is shown that the order is AF for D/Ce above 2.8 and that TN increases from 3.0 K for D/Ce=2.88 to 4.7 K for D/Ce=2.91. This means that the conduction electrons play a minor role in the AF ordering of CeD2+x and that the order is strongly affected by defects at the octahedral sites, being D atoms for D/Ce≥1.95 and vacancies for D/Ce≤3.0. On the other hand, the ground state Γ8 and the crystal-field splitting Δ≊240 K are not affected by the octahedral D atoms in the whole concentration region. This agrees well with the band-structure calculations, which claim that the D atoms at the tetrahedral sites are negative, whereas the octahedral D atoms are neutral.
Superconductivity associated with ferromagnetic domain walls in HoMo6S8 and (Er1−xSnx)Er4Rh6Sn18
Authors: Genicon J. L. , Modondanon J. P. , Tournier R. , Chaudouet P. , Fruchart R. , Peña O. , Horyn R. , Sergent M.
Published: July 2002

The compounds HoMo6S8 and (Er1−xSnx)Er4Rh6Sn18 (respectively, Ho-Mo-S and Er-Rh-Sn in the following) are known to be reentrant superconductors, the superconductivity being destroyed by the onset of long-range ferromagnetic order at low temperature. For the first time, the percolation of domain ‘‘walls’’ superconductivity has been produced below 0.2 K in Ho-Mo-S single crystals, confirming a systematic study of sintered samples and theoretical expectations. In addition, the ac susceptibility of Er-Rh-Sn single crystals, measured below 0.5 K, is large and positive for large ac fields and nearly equal to −1/4π for low ac fields. This fact confirms the existence of superconducting domain ‘‘walls’’ which screen the ac field.
Ho-ion dynamics in HoxLu1−xRh4B4
Authors: Heffner R. H. , Cooke D. W. , Hutson R. L. , Schillaci M. E. , Smith J. L. , Richards P. M. , MacLaughlin D. E. , Dodds S. A. , Oostens J.
Published: July 2002

New μSR measurements of Ho-ion dynamics in HoxLu1−xRh4B4 are reported for x=0.02 and 0.005. These compounds are superconducting below Tc≂11 K. The measured concentration dependence of the Ho3+ spin-lattice relaxation rate Γ0 is consistent with single-ion, conduction electron scattering (the Korringa mechanism) as the dominant process. Above about 10 K, Γ0 is activated with an energy of 66 K, about 1/2 of the overall crystal-field splitting. Below about 10 K (in the superconducting state) a more gradual temperature dependence is observed, as reported previously for x=0.70 and x=0.02. This temperature dependence is not consistent with the usual exponential decay in the superconducting state. Using a model of conduction-electron-exchange scattering which includes the full crystal-field potentials, we show that a reasonably quantitative understanding of the overall temperature dependence can be achieved.
Magnetic susceptibility of CeT3B2 and UT3B2 compounds (T=Co, Ru, and Ir)
Authors: Yang K. N. , Torikachvili M. S. , Maple M. B. , Ku H. C.
Published: July 2002

The magnetic susceptibility χ of CeT3B2 and UT3B2 compounds (T=Co, Ru, and Ir) has been measured as a function of temperature T for 2 K≤T≤300 K. For each sample, χ is weakly temperature dependent above ∼100 K, and approaches a finite value as T→0, indicative of a nonmagnetic ground state. The intrinsic susceptibility χ0, after correcting for the effect of the impurities at low temperature, ranges from 5.05×10−4 cm3/mole for CeRu3B2 to 1.33×10−3 cm3/mole for UIr3B2. The ratio S=π2k2Bχ0/3μ2Bγ (γ is the electronic specific heat coefficient), a rough gauge of exchange enhancement, ranges from 0.9 for CeIr3B2 to 4 for CeCo3B2.
Direct observation of Stoner excitations in itinerant ferromagnets by spin-polarized inelastic electron scattering (invited; abstract)
Authors: Hopster H.
Published: July 2002

Stoner excitations in the ferromagnetic 3d metals, although fundamental in the theory of itinerant magnetism, have never been observed directly, e.g., by inelastic neutron scattering because the energies involved are too high for present-day neutron sources. We show that these excitations are readily measure by spin-polarized electron energy loss spectroscopy (SPEELS). We have measured the spin polarization spectrum of electrons scattered from a Fe-based ferromagnetic metallic glass (Fe82B12Si6) using unpolarized primary electrons in the energy range Ep=20–240 eV. While the spin polarization P for elastically scattered electrons is always small (*P*≤3%) a maximum of P is found around 2.2 eV energy loss. The value of the maximum Pmax decreases with increasing primary energy (Pmax=12% for Ep=20 eV, Pmax=3% for Ep=240 eV). This maximum is caused by spin-flip (Stoner) excitations (via exchange). In this process an incoming spin-down electron falls into the empty part of the spin-down density of states above EF and excites a spin-up electron from the occupied part of the majority density of states. The energy loss of 2.2 eV then corresponds to the ferromagnetic exchange splitting. This interpretation is corroborated by recent model calculations by Glazer and Tosatti which show good agreement with the experimental data. The spin polarization as a function of energy loss and the dependence on proimary energy are well reproduced by the calculatioons. Kirschner et al. showed that the Stoner excitatioons can also be observed by a slightly different experimental approach, i.e., by using spin-polarized primary electrons and measuring the asymmetry of the scattered intensity upon reversal of the primary spin polarization. For a Ni(110) surface they found an asymmetry maximum around 300 meV energy loss. This value again corresponds to the ferromagnetic exchange splitting. The novel technique of spin-polarized electron energy loss spectroscopy, which is complementary to spin-polarized photoemission and inverse photoemission, promises to yield new insights into the electronic structure and the electronic excitation spectrum of itinerant ferromagnets and their temperature dependence, e.g., for ferromagnetic alloys.
Micron-order relief-patterned silica glass using a sol-gel method
Authors: Ohno Masayoshi , Yamada Takeshi , Kurokawa Takashi
Published: July 2002

A new method is presented for fabricating micron-order, relief-patterned silica glass using a sol-gel process. The relief pattern is clearly replicated from a master pattern onto the silica glass surface. Gel shrinkage during fabrication makes it possible to obtain a reduced pattern in comparison with the master. The reduction ratio is in the range between 1/2 and 1/3. Using this method, an echelette grating with a period of 9.55 μm was successfully fabricated from the master grating, having a period of 20 μm.
Deep levels introduced into silicon during hydrogen plasma annealing
Authors: Hwang J. M. , Schroder D. K. , Biter W. J.
Published: July 2002

We report the introduction of deep energy levels into silicon following a hydrogen plasma anneal at 300 °C for 3 h. The wafers were heat treated prior to the hydrogen anneal to cause oxygen to precipitate using a three-cycle high-low-high anneal. The deep level impurity concentrations generally exhibited a decreasing density into the wafer, indicative of damage originating from the surface. These findings are in contrast to other reported hydrogen plasma anneal results which generally show a reduction of deep level concentrations.
Pressure derivatives of the elastic moduli of a polycrystalline aggregate of hexagonal metal: Calculations using monocrystal elastic-constant pressure derivatives
Authors: Ramji Rao R. , Janardhana V.
Published: July 2002

The pressure deriviatives of the bulk, shear and Young’s moduli, and of Poisson’s ratio of a number of polycrystalline metals have been calculated using Hill’s approximation. The pressure derivatives of the second-order elastic constants of the corresponding single-crystal hexagonal metals have been used for this purpose.
Effects of thermal annealing on Si-doped GaAs grown by molecular beam epitaxy
Authors: Shinozaki K. , Mannoh M. , Nomura Y. , Mihara M. , Ishii M.
Published: July 2002

Low-temperature (∼4 K) photoluminescence has been studied on as-grown and thermally annealed Si-doped GaAs grown by molecular beam epitaxy. The peak intensities of the defect-related emissions, due to the defect-induced bound exciton (d, X) and the defect complex (d) are decreased by thermal annealing. On the other hand, Hall measurements show that free carrier concentrations are decreased only slightly by thermal annealing.
Method of description of the off-equilibrium property of stochastic processes with the use of Bayes’ probability
Authors: Agu Mashahiro , Asami Shigeyuki
Published: July 2002

A method is developed to describe the off-equilibrium property of an open system by taking the difference between the forward and backward stochastic processes into account. Here the forward probability is concerned with an initially conditioned ensemble of fluctuations whereas the backward one is concerned with the finally conditioned ensemble of fluctuations described by the Bayes’ probability. An asymmetrical property between the correlation function of the forward process and that of the backward one is shown to be an experimentally useful measure of off-equilibrium property. The above method is applied to the time series of stationary brain waves to find that the brain waves in both the active and meditative state of the brain are regarded as off-equilibrium fluctuations. The violation of the principle of detailed balance results in the asymmetry between forward and backward conditional entropies.