bluuebunny/crossref_metadata_2025 huggingface dataset:
Disappearance of the barrier offset voltage in the on-state characteristics of a chalcogenide threshold switch for short relaxations of holding voltages
Authors: Vezzoli Gary C.
Published: February 2003

New data are presented to show that the transient on-state characteristics of a chalcogenide threshold-switching device change significantly when the device is addressed with diagnostic pulses or continuous waves that reduce the voltage beneath the holding level for no longer than 10–20 nsec. In this regime there is no indication of an offset barrier voltage which characterized the blocked on state for longer relaxation intervals. The results suggest the absence of any necessity for a barrier phenomenon and are interpreted in accord with the phase-transition model for threshold switching rather than the double-injection theory.
Fabrication and electrical properties of epitaxial PbTe metal-insulator-semiconductor structures
Authors: Zimmermann P. H. , Mathews M. E. , Joslin D. E.
Published: February 2003

Methods for the fabrication of metal-insulator-semiconductor structures with the use of eptaxial PbTe films are described. These methods obviate the need for treating the semiconductor surface. They involve epitaxial film growth in a vacuum environment by hot-wall epitaxy followed by (1) deposition of ZrO2 without breaking vacuum and (2) deposition of pyrolytic SiO2. Capacitance-voltage characteristics in both cases closely correspond to theoretical values. Depletion-layer generation is shown to be the dominant contribution to the inversion conductance.
Sputter deposition of thin films of superconducting Er(RhB)4
Authors: Christner G. L. , Bradford B. , Toth L. E. , Cantor R. , Dahlberg E. D. , Goldman A. M. , Huang C. Y.
Published: February 2003

Thin films of essentially single-phase ErRh4B4 have been sputter deposited from an arc-melted target of ErRh4B4 in an ultrahigh-vacuum system incorporating a liquid-nitrogen cryogettering can. Optimum conditions for depositing the films were determined. The films exhibit reentrant superconducting transitions with Tc’s somewhat different from those reported for bulk material.
Graded or stepped energy band-gap-insulator MIS structures (GI-MIS or SI-MIS)
Authors: DiMaria D. J.
Published: February 2003

A new concept in nonvolatile semiconductor memory using graded or stepped energy band-gap insulators under the gate electrode of a metal-insulator-semiconductor type structure is described. With the graded or stepped insulator, electrons or holes can be injected from the gate electrode at low to moderate applied fields. These carriers then flow under the applied voltage bias into a wide energy band-gap insulator (such as SiO2) with a purposely introduced charge trapping layer (such as ion-implanted As, deposited W, or deposited polycrystalline Si). This trapping layer captures and stores electrons (’’write’’ operation) or holes (’’erase’’ operation) with as close to 100% efficiency as possible. Because of the larger energy barriers at the semiconductor (such as Si) interface with the wide energy band-gap insulator (such as SiO2), few carriers of the opposite sign are injected. Therefore, the substrate Si-SiO2 interface, for instance, can be used strictly for charge sensing (’’read’’ operation) such as in a field-effect transistor. Several experimental examples are mentioned. A detailed description of stepped insulator structures using thin Si3N4SiO2 (≈5.2 eV band gap) layers on (≈9 eV band gap) with an ion-implanted As region is given. Some advantages of these structures over other nonvolatile semiconductor memory devices are discussed.
Resistance dependence of detected signals of MOM diodes
Authors: Yasuoka Y. , Sakurada T. , Siu D. P. , Gustafson T. K.
Published: February 2003

The detection characteristics of point-contact W-Ni diodes at 10 MHz, 9.5 GHz, and 28.3 THz are investigated as a function of diode resistance (contact pressure). The experimental results are compared with predictions from tunneling theory taking into account circuit parameters. Good agreement is obtained when the relaxation behavior of the metallic whisker antenna is considered at infrared wavelengths.
Modification of CdSe resistivity by laser annealing
Authors: Feenstra R. M. , Parsons R. R. , Shepherd F. R. , Westwood W. D. , Ingrey S. J.
Published: February 2003

The resistivity of CdSe thin films, vapor deposited on insulating substrates, has been reduced by more than two orders of magnitude by irradiation with a cw argon-ion laser. A threshold power density of about 0.6 W for a beam diameter of 250 μm is necessary to cause a measurable decrease in the resistivity of a 0.4-μm-thick film; above this value, the resistivity decreases rapidly with increasing power to a minimum value. Electron and x-ray diffraction analyses show that there is an increase in film grain size by only a factor of 2 on annealing, but SEM and Auger studies indicate that there are significant changes in the surface topography and composition. Calculations show that the power absorbed by the CdSe film is sufficient to cause melting. The decrease in resistivity can be attributed to the effect of Se vacancies created by preferential loss of Se from the film surface at these elevated temperatures.
N2 laser-controlled semiconductor switching of 10-μm radiation
Authors: Corkum P. B. , Alcock A. J. , Burnett N. H.
Published: February 2003

Nanosecond pulses of 10-μm radiation can be generated by switching the output of a low-pressure CO2 laser with a N2-laser-controlled semiconductor reflection switch. These pulses have been used to injection mode lock the ∼50 J output of a 5-liter TEA CO2 oscillator. The 10-μm reflectivity of the optically generated charge carriers is found to be a function of the wavelength of the switching laser, while 10-μm transmission data has been used to monitor surface recombination before and after laser annealing of a germanium sample.
Microwave harmonic generation in a plasma-filled waveguide
Authors: Sharma R. R. , Sharma R. C.
Published: February 2003

A high-power microwave propagating through a plasma-filled waveguide gives rise to the generation of second and third harmonic waves because of ponderomotive force and energy-dependent collisions, respectively. The generated harmonics possess a very different kind of intensity distribution than that of the normal modes. The efficiency of second harmonic generation is resonantly enhanced at some optimum size of the waveguide such that 2β1=β2, i.e., n2π2/b2+(m2−4) π2/a2= 3ωp2/c2 where β1 and β2 are the propagation constants of fundamental and second harmonic modes. This effect might account for the observed high yield of second harmonic generation in laser-produced plasmas. The third harmonic power, however, shows a monotonic rise (tending towards a saturation value) with the width of the waveguide.
A solid-state solar-powered heat transfer device
Authors: Belić Milivoj , Gersten Joel I.
Published: February 2003

A solar-powered solid-state heat transfer device capable of operating in either a refrigeration or a heat-pump mode is proposed. The device’s operation is based on the combined utilization of the photovoltaic and Peltier effects.
Synchroton-?erenkov detectors for electrons
Authors: Rynne T. M.
Published: February 2003

In the presence of an ambient medium and an external magnetic field, ultrarelativistic charged particles emit synchrotron-?erenkov radiation. For cases in which the classical synchroton frequency greatly exceeds any characteristic absorption frequency of the medium, i.e., when the medium can effectively be treated as a free-electron gas, the photon production rates depend sensitively on the ratio of the synchroton frequency to the relativistically boosted electron plasma frequency. In principle this connection can be exploited for the construction of high-energy electron detectors (E≳2 GeV). These counters allow for the simultaneous determination of the electron energy, and a mass discrimination between electrons and higher-mass singly charged particles. The relative merits of synchrotron-?erenkov detectors and some standard counters are briefly discussed.
Numerical evaluation of Lindhard’s theory of stopping power for a charged particle in a free-electron gas
Authors: Iafrate G. J. , Ziegler J. F.
Published: February 2003

Stopping powers derivable from Lindhard’s dielectric theory of stopping for a charged particle in a uniform electron gas are calculated as a continuous function of electron density for a wide variety of projectile energies ranging from 102 to 104 keV/amu. Results are presented for electron densities varying from 1022 to 1032 electrons/cm3, a range which includes electron densities generally found for the energy bands of solids and for the atomic levels of atoms.
Relative transition probabilities for the x-ray lines from the K level
Authors: Heinrich Kurt F. J. , Fiori C. E. , Myklebust R. L.
Published: February 2003

The ratio of emission of the electron-excited Kβ lines to the sum of Kα and Kβ lines was measured for several elements with a lithium-drifted silicon detector. The measured intensities were corrected for background, line overlap, and absorption within the target and within the detector. The results are compared with those obtained by other investigators.
Fourier-Bessel series solution of an exterior Dirichlet boundary-value problem with rotational symmetry
Authors: van der Merwe J. P.
Published: February 2003

The rotationally symmetric solution φ (r,z) satisfying ∇2φ=0 in the region exterior to a cylinder of radius A on which the boundary values are given by φ (A,z<0) =φ (A,z≳L) =0 and φ (A,z) =F (z) for 0<z<L is represented by a Fourier-Bessel integral, which can be approximated by a Fourier-Bessel series. It is shown how the quality of the approximation can be improved by ensuring that the period of the series is sufficiently large. For a finite period the error of the approximation can be understood either in terms of induced charge distributions on two parallel planes, or by considering an infinity of image charge distributions at r=A. The error can be reduced by eliminating the images of potential distributions, which is done numerically through the addition of a suitably chosen auxiliary Fourier-Bessel series.
Numerical analysis of the output performance of a pulsed HBr chemical laser
Authors: Iyoda M. , Udagawa M. , Obara M. , Fujioka T.
Published: February 2003

The results are reported of a theoretical study on the pulsed HBr chemical laser using a mixture of H2 and Br2, utilizing numerical analysis by pulsed chemical-laser code. The HBr laser output performance as characterized by laser energy, power, pulse width, and vibrational population distribution was examined as a function of the initial dissociation rate and the H2/Br2 mixture ratio for a mixture at 100 Torr. The effect of HBr(0) in an HBr chemical laser must be taken into account, especially in applying HBr chemical lasers to the optical pumping of CO2 and HBr gases, since the 4.2-μm laser emission useful for such pumping comes from the P1−0(J) and P2−1(J) lines. In this paper, the effect of added HBr(0) on output performance was also studied.
Defect trapping of ion-implanted deuterium in Fe
Authors: Myers S. M. , Picraux S. T. , Stoltz R. E.
Published: February 2003

The trapping of ion-implanted deuterium (D) by lattice damage in Fe was investigated in the temperature range 90–500 K. The D depth profile was determined by measuring the proton yield from the 3He-excited nuclear reaction D(3He,p)4He, and the D lattice location was obtained by ion channeling. Linear ramping of the temperature produced a sharp detrapping stage at 260 K and a broader release extending over 350–450 K. The release-vs-temperature data were analyzed by solving the diffusion equation with appropriate trapping terms, yielding 0.48 and ?0.81 eV for the binding enthalpies associated with the two stages. The 0.48-eV trap corresponds to D at a near-octahedral interstitial site, where it is believed to be associated with a vacancy.
Light scattering from surface and bulk thermal magnons in iron and nickel
Authors: Sandercock J. R. , Wettling W.
Published: February 2003

We report on light scattering measurements on thin polycrystalline samples of iron and nickel. Both the surface and bulk magnons are observed. The measured magnon energies as a function of magnetic field, and of wavevector magnitude and direction, are in good agreement with the calculated values. The predicted exchange induced decay of the surface magnon is observed. In nickel the observed frequencies and linewidths are strongly strain dependent. Oxide layers have an almost negligible effect on the spin wave frequencies in both iron and nickel.
Magnetostriction and thermal expansion of ordered Fe3Al
Authors: Cook J. M. , Pavlovic A. S.
Published: February 2003

The magnetostriction and thermal expansion of single crystals of ordered Fe3Al (24.88 At.%Al) at temperatures between 296 and 77 K are presented. It is shown that two magnetostriction constants adequately describe the magnetostriction at any temperature. Both magnetostriction constants and thermal expansion as a function of temperature exhibit an anomaly at about 220 K which has a thermal hysteresis. Magnetization measurements versus temperature curves do not indicate an anomaly. It is speculated that this anomaly is due to some structural transformation which is yet unrevealed.
Real-space renormalization-group method for quantum systems : Yang-Lee edge singularity
Authors: Uzelac K. , Jullien R. , Pfeuty P. , Penson K. A.
Published: February 2003

A T=0 real-space renormalization-group method is presented and applied to the quantum 1D transverse field Ising model in the presence of a longitudinal field. This is an indirect way to study the equation of state of the equivalent 2D classical Ising model at finite temperature. When the longitudinal field is purely imaginary we obtain a new critical behavior which is related to the Yang-Lee edge singularity of the corresponding classical model. We extract the edge exponent σ in agreement with previous series expansion estimates.
The effect of annealing conditions on the magneto-mechanical properties of Fe-B-Si amorphous ribbons
Authors: Brouha M. , van der Borst J.
Published: February 2003

The effect of annealing conditions on the effective magneto-mechanical coupling factor, Young’s modulus at constant external magnetic field and constant induction (cH and cB), the magnetic anisotropy and the incremental permeability are reported of Fe80B20, Fe80B15Si5 and Fe80B10Si10. The effect of transverse field annealing (parallel to the ribbon width) on keff is relatively small in F80B20 and Fe80B10Si10. It results in keff values ranging from 0.5 to 0.6 and from 0.4 to 0.55, respectively. In Fe80B15Si5 field annealing causes a marked increase in keff reaching a maximum value of 0.86 at a bias field of 60 A/m after annealing at a temperature of 350° C for 2 min. The relative change in cH then reaches a maximum as well, arriving at the extremely large value of (csatH−cminH)/cminH = 4.5 (’’ΔE effect’’). These values are higher than previously reported for Fe78B12Si10, which were at that time the highest known1,2.
Time dependent magnetization of iron particles in mercury ferromagnetic liquids
Authors: Hoon S. R. , Popplewell J. , Charles S. W.
Published: February 2003

Ferromagnetic liquids containing tin-coated iron particles of 45 A median diameter dispersed in mercury have been prepared electrolytically. After the liquids have been subjected to an abrupt stepwise reduction in an applied magnetic field the magnetization decays with a relaxation time of ∼60 s. Such long decay times cannot be explained if it is assumed that the system consists of separate particles. Long relaxation times of 60 s could arise if the particles form aggregates of approximately 104A diameter which relax by Brownian rotation when the applied field is removed. Further evidence for the the existence of 104A diameter aggregates has been obtained from an analysis of sedimentation and viscosity measurements. However, the possibility that the time dependence is due to conformational changes in the aggregates as the applied field is reduced is not ruled out and is considered a likely alternative explanation.
Angular variation of the coercive force and remanence in borohydride reduced iron particles
Authors: Baltz A. , Doyle W.
Published: February 2003

The angular dependence of the coercive force and remanence on borohydride reduced iron particles was measured as a function of mulling time. Typically the saturation moment of the powder was 150 emu/gram, while the coercive force and remanence of the unoriented powder was 500 Oe and 0.48, respectively. 50% by weight of the powder was dispersed in an epoxy binder using mulling cycles N=0–300, spread on a polyimide film and oriented in a 2000 Oe field. The remanence in the parallel direction increased from 0.60 for N=0 to 0.74 for N=300. The remanence varied monotonically from a maximum in the parallel (ϑ=0°) to minimum in the perpendicular direction (ϑ=90°). The coercive force (Hc) showed a peak at ϑ=55° and showed a decrease at ϑ=0° and ϑ=90°. The coercive force decreased with mulling cycles and Hc(0°)/Hc(90°) <1. Ball milling the powder produced qualitatively the same results.
Mössbauer spectroscopic and magnetokinetic studies on the oxidation of pyrite (FeS2)
Authors: Marusak L. A. , Mulay L. N.
Published: February 2003

In an earlier publication 1 we reported aspects of magnetokinetic studies on the oxidation of FeS2 carried out as a function of its particle size (90 to 250μm) and temperature (400–500 °C); in this study we considered mostly the formation of α and γ Fe2O3. In the present paper we have considered the formation of other oxidation products such as (a) Fe2  (SO4)3, and (b) superparamagnetic particles of α Fe2O3. Mössbauer spectroscopy has confirmed the presence of (a) and, coupled with X-ray line broadening studies has shown the absence of (b). The yield of Fe2  (SO4), is found to increase with decreasing starting particle size of FeS2. Using our earlier results 1 we have obtained values of (dM/dt) from the initial slopes of the magnetization (M) vs. time curves for particle sizes (180 to 250 μm). From plots of ln (dM/dt) versus 1/T an activation energy of ∼7 Kcal/mole has been obtained for the following predominant reaction: FeS+(11/4)O2→ (1/2) αFe2O3+2SO2. This value compares favorably with values reported by other workers2 who used classical thermogravimetric analysis.
Bubble device materials with orthorhombic anisotropy
Authors: Voermans A. B. , Breed D. J. , van Erk W. , Carpay F. M. A.
Published: February 2003

The growth characteristics and the magnetic properties of Mn-substituted garnet films grown on (110) oriented substrates are reported. On perfectly oriented substrates hillocks are observed which occur due to the fact that (110) is a habit face. By the introduction of a slight misorientation of the substrates, the hillocks disappear and the surfaces are perfectly flat. Mn is substituted in the garnet to obtain the right magneto-elastic properties. It is shown that the temperature dependence of the magnetic parameters can be adjusted such as required to provide a device material.
LPE growth of double layer structures from molybdate and lead borate fluxes
Authors: Korenstein Ralph , Castro Carlos A.
Published: February 2003

Composite structures consisting of YIG and (YSmLuCa)3(FeGe)5O12 layers were prepared from two different fluxes. YIG was grown from a lithium and yttrium molybdate flux. (YSmLuCa)3(FeGe)5O12 which supports 2.5 μm bubbles was grown from conventional lead borate flux. The very slow growth rates obtainable from molybdate flux makes it ideal for the deposition of submicron thick YIG layers. YIG grown from this flux was found to contain lithium. The lithium content appears to correlate with the observed magnetic and electrical properties. A technique for measuring submicron thick YIG films is described. The effects of YIG on hard bubble suppression in (YSmLuCa)3(FeGe)5O12 is reported.
Eddy current damping in Ca-doped YIG films
Authors: Hsia L. C. , Wigen P. E. , De Gasperis P. , Borghese C.
Published: February 2003

A series of Ca-doped YIG films in which the atomic ratio of Ca to Y in the melt varied from 0 to 1.18 were grown. Resistivities of the virgin state of these films were measured. The dependence of the linewidth when the field is applied at 30° from the film normal on the Ca/Y atomic ratio was found to be linear and the dependence of the field is applied normal to the film surface. These are clear indications of the eddy current damping mechanism. The linewidth contribution due to this mechanism is given by ΔHe.c.= (2π/c2γ) σAω2 where σ is the conductivity, A is the disc area, ω is the radial frequency and the magnetic field is applied normal to the film plane.
Perpendicular anisotropy in an epilayer of magnesium ferrite
Authors: Baszyński J. , Szymański B.
Published: February 2003

Magnetic anisotropy was studied in a monocrystalline, epilayer of magnesium ferrite. This epilayer, 1.2 μm thick, was prepared by CVD on /100/ cleavage surfaces of MgO substrates at 1550 °K. Anisotropy measurements were performed by FMR and torque methods at room temperature. The parameters characterizing this epilayer are: 4πM=1650 G, K1=−3.2×104 ergs/cc, Kn=1.2×105 ergs/cc and a quality factor q=1.1.
Abstract: Ferrite epilayers for bubble application
Authors: Baszyński J.
Published: February 2003

In last decade years, we have payed attention to new bubble materials: monocrystalline epilayers and monocrystalline platelets of ferrites with spinel structure. In these materials cylindrical magnetic domains have been obtained. The perpendicular magnetic anisotropy occuring therein is a primary parameter, defining the properties of these bubble materials. The source of this anisotropy does not reside in the crystallographical structure of the materials, which are ferrimagnetics with cubic structure. The epilayers were obtained by CVD method on monocrystalline MgO substrates on the /100/ crystallographical surface in the 1100–1340 C temperature range. The dominant source of the perpendicular anisotropy observed in epilayer formed by CVD onto nonmagnetic substrates is magnetostriction. Can be summarized as follows: 1/ epilayers of ferrites are normally in a state of mechanical stress σ due to mismatch between lattice constants. 2/ if the ferrite epilayer is magnetostrictive this stress produces a uniaxial magnetic anisotropy, 3/ with negative magnetostriction constants the easy axis is normal to the epilayer plane if this epilayer is in tension σ≳0. The parameters characterizing the ferrite epilayers are: thickness 5 to 20 μm; 4πM=0.4 to 2 kGs; K1=104 to 105 ergs/cc; Kn=104 to 105 ergs/cc; collapse field Hcol=0.4 to 2 kOe; characteristic length 0.04 to 0.05 μm; bubble diameter 1 to 7 μm; bubble mobility, measured by FMR, is 40 to 250 cm/Oes and quality factor q about 1.
Comparison between transport and F.M.R. methods for the dynamic characterization of bubble materials
Authors: Challeton D. , Jouve H. , Magnin J.
Published: February 2003

Transport methods using high speed photography and ferromagnetic resonance are compared for the determination of the dynamic characteristics of bubble materials. The mobility and the saturation velocity are calculated with the use of parallel and perpendicular magnetic resonance fields and linewidth. Experiments are performed with 2-μm bubbles Ga, Al or (Ca, Ge) substituted (Eu, Lu)3 Fe5 O12 and (Y Sm Lu Ca)3 (Fe Ge)5 O12 garnet films. In films experimented with, the mobilities range between 400 and 1000 cm/S Oe and the saturation velocities between 800 and 2000 cm/s. A good agreement has been found between both methods.
Static and kinematic parameters of magnetic bubble walls having a horizontal Bloch line pair
Authors: Blake T. G. W. , Torre E. Della
Published: February 2003

The micromagnetic model previously reported has been applied to a selection of materials and to an additional wall type. The stability of unichiral (S=1) walls and walls containing a single horizontal Bloch line pair (HBLP) has been studied numerically for Q in the range 1.4 to 4.6, and for material lengths, normalized to film thickness, between 0.05775 and 0.462. Wall structure, in the form of contour maps and profiles of azimuthal angle, have been obtained for walls without and with a 2π twist (HBLP) centered on the film midplane. The dependence of structural quantities on material parameters is also presented. Bubble mobility dependence on quasi-static wall structure was investigated from the point of view of the gyrovector force density concept. The dependence of the peak magnitude of the gyrovector on material length is discussed, and a relief map of the gyrovector magnitude for a wall containing an HBLP is presented.
Abstract: Stroboscopic measurements of strip domain expansion in chevron stacks
Authors: Clegg W. , Mohamad W. F. , Warne D. H.
Published: February 2003

Domain motion and stretching in chevron expander stacks is characterized over the frequency range 100 kHz to 500 kHz. Lateral motion through the stacks shows stable resting positions at the two ends and at the centre of the chevrons with the strip transferring quickly between these. The transfer requires a progressively longer phase angle as the frequency is increased and this reduces the resting phases, e.g. the resting phase at the apex is 45° at 100 kHz, but only 10° at 500 kHz. Transverse expansion takes place principally during the pauses at the ends of the chevrons. The form of the stretching is largely linear with phase, but slows to a limiting value before a lateral transition occurs. The speed of expansion at different frequencies is fairly constant at about 40 m/sec. in the linear region at 40 Oe drive and mid-bias. However, the linear region reduces in phase-width at increased frequencies to allow only minimal expansion, combined with a small contraction when crossing the gap between stacks, at frequencies above 400 kHz in these specimens. At low bias the degree of expansion tends to a limit, corresponding to a maximum domain-tip speed of approximately 52 m/sec. The stretching of the two ends of the strip is not truly symmetrical. At low bias the expansion in the direction of the chevron apexes is slightly greater, and at high bias the situation is reversed. These differences are related to different phase and velocity variations with bias in the two directions.
Magnetostriction behavior in isotropic and cube-on-face 3% SiFe laminations
Authors: Allia P. , Ferro A. , Soardo G. P. , Vinai F.
Published: February 2003

The anomalous negative magnetostriction elongation Δl/l previously observed on Goss texture sheets, associated with the formation during magnetization of transverse spike domains, has been investigated in non-oriented and cube-on-face 3% SiFe laminations. On isotropic sheets, the appearance of a negative Δl/l peak, centered at relatively high inductions B, is essentially masqued by the positive contribution due to the reorientation of a main domain structure, containing many regions whose magnetization forms large angles, up to 90°, with respect to the sheet axis. However, upon application of a tensile stress, a large fraction of these domains can be suppressed and a negative magnetostriction peak appears. The effect is identically observed on cube-on-face laminations. These results show that the presence of an anomalous negative magnetostriction peak is a general phenomenon, not limited to the case of Goss texture laminations. Therefore the formation of transverse spike domains at intermediate inductions is shown to characterize the magnetization process also in isotropic and cube-on-face 3% SiFe materials.
Abstract: Magnetostriction and magnetization of CeFe2
Authors: Melville D. , Al-rawi K. M. , Khan W. I.
Published: February 2003

While investigating the high field magnetostriction of the highly magnetostrictive cubic laves phase compounds of the type RFe2 a sharp increase in the magnetostriction of polycrystalline CeFe2 was observed at fields of around 3 T and at temperatures below 150K. The first order change in strain increases with decreasing temperature and at 5K it amounts to approximately 150×10−6 which corresponds to a 200% increase in the parallel magnetostriction. The field at which the transition occurs decreases slowly with decreasing temperature. Magnetisation curves also show signs of a first order increase at the same fields but the change in magnetisation is only of the order of 8% at 5K.

Above approximately 150K the easy-direction of CeFe2 changes1 from [100] to a non-symmetry direction of the type [uuw]. This can be accounted for if the third order cubic anisotropy constant (K3) is significant. A tentative explanation for the observed discontinuities is presented in terms of first-order rotations of the magnetisation vector, made possible by relatively large values of K3.

1U. Atzmony and M. P. Dariel, Phys. Rev. B. 13, 4006 (1976).
Wave number and temperature dependent Landau-Lifshitz damping in nickel
Authors: Heinrich B. , Meredith D. J. , Cochran J. F.
Published: February 2003

Using the technique of microwave transmission at FMAR, we have measured the temperature dependence of the Landau-Lifshitz damping parameter λ in nickel. It was found that the magnitude of λ increased by a factor 4 over the temperature range 300 K–77 K. The microscopic theory of spin wave damping indicates that there are two contributions to the damping parameter; the one proportional to the resistivity and the other to the wave number dependent conductivity. We compare our experimental results with this theory and with the previous work of Bhagat using FMR.
Electron spin resonance in Cd1−xMnxTe
Authors: Oseroff S. , Calvo R. , Giriat W.
Published: February 2003

We have performed electron paramagnetic resonance measurements in single crystals of Cd1−xMnxTe at 9 GHz between 1.6 and 290 K for a wide range of manganese content (0.0005?x?0.60). The temperature of the order-disorder transition, Tc, and the critical exponent α, were determined from the temperature dependence of the EPR linewidth. At x=0.2 we find a discontinuity in Tc suggestive of a percolation critical point.
Ferromagnetic relaxation in single crystals of In-substituted BiCa VIG
Authors: Mo Yu-Jun , Lai Wu-Yan , Cao Ke-Ding
Published: February 2003

We report some experimental results on the ferromagnetic relaxation in single crystals of In-substituted BiCa VIG. These crystals, grown in our laboratory exhibit very attractive properties from the practical point of view, e.g. low anisotropy, low resonance linewidth and low saturation magnetization. We measured the temperature dependence of the resonance linewidth ΔH at X-band from liquid He to room temperature. It was found that there was a low-temperature peak in ΔH near 12 K. This is quite different from the results reported for many other garnets. We suggest that this is due to the ’’intra-ionic slow relaxation’’ mechanism of the valence-change vanadium ions in In-BiCaVIG. The linewidth ΔH was also measured as function of frequency from 0.5 GHz to 10 GHz and the Sparks-Loudon-Kittel two-magnon linewidth peak was observed. In this frequency range, ΔH had a general tendency to increase linearly with increasing frequency except in the vicinity of the peak.
Experimental determination of the mechanism of ME effect of Cr2O3 from ME susceptibility and electric shift in the antiferromagnetic resonance
Authors: Kita E. , Siratori K. , Tasaki A.
Published: February 2003

The mechanisms of the ME effect of Cr2O3 were experimentally determined at 4.2 K. For this purpose, ME susceptibility was measured statically by SQUID from 1.6 to 270 K and the electric shift of AFMR was observed at 4.2 K by an ac modulation method. The former experiment gave α∥(4.2 K) =−0.8, α∥(255 K) =15.3 and α⊥(4.2 K) =−4.7 in 10−4 cgs unit. The latter gave a frequency shift of −1.02×10−6 cm−1 at E=1 cgs in the case of both E↘ and H↘ parallel to the c axis. From these experiments, δg=−1.05×10−8 and δD=−3.3×10−6 cm−1 were deduced for E=1 cgs along the c axis. This value is not only too small but of the wrong sign to explain the sign and the magnitude of α∥ at higher temperatures. α⊥ at 4.2 K seems too large to be interpreted by the tilting of the easy axis of spins and the role of other mechanisms such as the appearance of a Dzyaloshinski interaction is suggested.
Visualization of the 180-degree antiferromagnetic domains by means of new magnetooptical effect
Authors: Eremenko V. V. , Kharchenko N. F. , Beliy L. I.
Published: February 2003

In magnetically ordered crystals, which are deprived of anti-inversion as a symmetry operation, a new magnetooptical effect is permitted. It consists in appearance of a birefringence of the linear polarized light directly proportional to the magnetic field strength as opposed to the quadratic Cotton-Mouton and Voight effects. The appearing birefringence is connected with inducing the nonequivalency of magnetic sublattices by a magnetic field. The sign of the linear magnetooptical effect depends on the directions of the sublattice magnetic moments and the magnetic field strength. It is determined by sign of the antiferromagnetic vector projection on some axis only if the magnetic field direction is constant. This circumstance gives a possiblity of visualizing the regions of the crystals having oppositely oriented antiferromagnetic vectors. The visual observation of the 180-degree antiferromagnetic domains in the two-sublattice antiferromagnetic cobalt fluorite by means the new linear magnetooptical effect is reported.
Report of the panel on high magnetic field research and facilities
Authors: Keller S. P.
Published: February 2003

The Panel, under the chairmanship of S. P. Keller, was created by the Solid State Sciences Committee, National Research Council, at the request of and with the support of the National Science Foundation. The Panel consisted of four subpanels: Scientific Opportunities, Raymond L. Orbach, chairman; Applications, John K. Hulm, chairman; Magnet Design and Materials, Bruce Montgomery, chairman; and High Magnetic Field Facilities and Users, Bruce D. McCombe, chairman. The major recommendations were I. A design program should be started to determine methods for producing steady state, highly homogeneous, magnetic fields up to 75 T. It is recommended that fields of 45 T and 60 T be the intermediate goals along the way to 75 T. II. The design and construction of quasistatic pulse magnets with fields approaching 100 T should be undertaken. III. The design and construction of short pulsed magnets affording fields greater than 1000 T should be undertaken. In addition to these primary recommendations, there were others dealing with i. The support of research in superconducting materials and processing techniques. ii. The funding of facilities for supporting equipment (e.g., optical spectrometers). iii. The support of research exploiting the high magnetic fields recommended above. iv. Funding for adaptation of energy sources developed for other applications to high magnetic field installations. Report published by National Academy of Sciences, Washington, D.C. (1979)
Abstract: Quasistatic magnetic fields
Authors: Praddaude H. C. , Foner S.
Published: February 2003

A prototype switching system has been developed which can switch 20 kA at 230 V for short periods of time through inductive loads. High power silicon controlled rectifiers are used to switch the National Magnet Laboratory dc generators on and off into a liquid N2 cooled, low impedance high field magnet so that high fields can be generated for a period of time approaching 1 sec. These transient ’’quasistatic fields’’ involve times which are intermediate between the usual pulsed field operation of milliseconds or less and the more limited field range produced by dc techniques. Each of the four specially designed low internal impedance dc generators can produce as much as 8 MJ/sec on a 5 sec transient mode of operation, which is sufficient to project development of magnets producing quasistatic fields approaching 40 tesla. The present switching arrangement can furnish between 0.5 and 10 megajoules for intervals between 0.1 and 2 seconds using 2 generators operating in parallel and drawing energy from the 84 ton flywheel attached to the generator set. Details of the switching hardware can be found in Ref. 1. Several liquid nitrogen precooled magnets have been tested at various field levels. The inner bores generally were 2 cm i.d. The copper conductor cross section and coil dimension determined the current, field and time at high fields. Square cross-section wire, multilayer coils were made as single sections for the lower current, lower field regime. Pancakes connected in parallel provide lower impedance and allow higher current magnets and higher fields. Other winding configurations use tape-wound, rectangular cross-section wire, or Bitter-plate type magnets. Fields above 30 T were generated on a quasistatic basis with such magnets. A detailed description of this work has been submitted for publication elsewhere.
Abstract: Copper-steel composites for generating intense pulsed magnetic fields
Authors: Melville D. , Rayner D. L. , Khan W. I. , Mattocks P. G.
Published: February 2003

In the generation of intense magnetic fields using copper wire-wound solenoids an upper field limit is often imposed by Lorentz forces in the conductor. The use of materials such as 2% Be-Cu alloy increases the maximum stress permitted fields, but their high resistivity leads to an unfavourable energy limitation. The use of copper-clad steel however enables the roles of conductor and strengthener to be separated and by varying the copper/steel ratio to be almost independently controlled. Using a given energy source the energy limitation is determined taking Joule heating into account by an iterative computer technique. The stress limitation is determined1 taking the Youngs moduli of copper, steel and insulation into account. Calculations have been made using a range of energy sources and pulse lengths of 1 ms and 10 ms. By varying the copper/steel ratio it is possible to design an optimum coil for which the energy and stress limitations coincide. It is found that in most cases, fields higher than those possible with pure copper wire are obtainable, with increases in maximum field of up to 30%. Practical examples of such coils will be presented and the problems associated with winding copper steel composite coils will be discussed. In addition it will be shown that the steel component has a well defined effect on the field profile of the solenoid at low magnetic fields.
Ancient techniques (invited)
Authors: Coey J. M. D. , Bouchez R. , Dang N. V.
Published: February 2003

Ancient ceramics may be characterised by their magnetic hysteresis loops. Spontaneous and remanent magnetization and coercivity can be used to distinguish groups of ceramics fired in different conditions. Information about the firing conditions is obtained by comparing the magnetic parameters of the sherds with those of laboratory-fired paeleosols. The method is illustrated with reference to contemporary red, buff and grey ware (c 3000 BC) from the period II of Tureng Tepe and Tepe Hissar, two related sites in northeastern Iran. In some cases the firing temperature can be estimated to within 50 C, and groups of sherds fired in oxidizing, reducing or mixed atmospheres are identified. An explanation of the firing temperature dependence of the hysteresis loop parameters in the range 400–1200 C is based on the proportions of iron diluted in silicates and in superparamagnetic or stable iron oxide particles, derived from magnetic and Mössbauer data. An assessment is given of the potential of simple magnetic measurements in archaeometry.
Abstract: Application of the methods and concepts of magnetism to provenance determination of archaeological artifacts
Authors: Evans B. J.
Published: February 2003

The magnetic properties of material artifacts depend on their bulk compositions, the phase assemblages, the crystal- and micro-structures of the phases and their thermal histories. The magnetic properties of an object formed from chemically pure elements and compounds are independent of the origins of the source materials. However, most archaeological artifacts are not made from pure elements and compounds and contain sufficient quantities of impurity atoms and ions to cause variations in magnetic properties that are traceable to variations in the impurity concentration of the source materials. Nevertheless, the relationship between the magnetic properties and provenance of an artifact reflects more than chemical composition. The utilization of data consisting of single numbers or low dimensional correlations among such numbers, i.e., as in chemical analysis, has severely hampered the progress of ’’sourcing’’ studies. The experimental techniques discussed overcome this limitation by providing data that are graphical and that include a large number of parameters as well as correlations among these parameters in a single measurement. These techniques include those of Mössbauer spectroscopy and temperature dependent magnetization studies. The data obtained in these two instances are graphical and exhibit simultaneously effects due to bulk composition, the phases present in a multiphase assemblage, crystal structure, magnetic structure, composition within a given phase and the microstructures of the phases. In many instances it is not necessary to perform extensive data analysis to establish a correlation between a possible source material and an archaeological artifact. The successful application of Mössbauer spectroscopy to provenance studies of iron ore artifacts from Mesoamerica will be discussed. It appears that this technique can also be extended to glass and a limited number of alloy artifacts. Thermomagnetic measurements have yet to be employed in provenance studies but the potential for application is clear.
Abstract: Effects of torsional stress on magnetic tape cores carrying electric current
Authors: Dalpadado R. N. G. , Shirae K.
Published: February 2003

Extensive investigations on the effects of torsional stress on magnetic tape cores carrying electric current are reported. A number of core samples including Metglass 2826, 2605, 2605A; three amorphous samples x, y, z belonging to the FeCo, Fe, and FeNi groups respectively; and several others including 50%Ni–Fe cores were studied. The following main phenomena are observed: (a) when a ferromagnetic tape core carrying an electric current is twisted, a shift in the two vertical portions of the corresponding B–H loop is observed, the shifts being simultaneous and usually in the same direction (b) the shifts are a function of both the magnitude of the conducting current and the applied torsion (c) the direction of the observed shift, rightwards or leftwards, depends on the direction of the current flow and the torsion (d) the shift is a function of the material of the core sample and its dimensions. Other subphenomena, peculiar to the type of core sample being studied, have also been noted. It is considered that the shifting of the B–H loops is due to the magnetization introduced by torsion interacting with the field due to the core current and the alternating drive field, resulting in asymmetric magnetic flux for each half of the exciting cycle. The above is shown by the proportionality seen for the sample magnetostrictions with respect to the corresponding shifts: the larger the value of magnetostriction the larger being the shift. For an exciting field of 198 ATm−1, 20 Hz, and a core current in the range of several hundred milliamperes, the shifts for the samples x, y, z are respectively in the ratio 1:2.5:8 which are in agreement with the magnetostriction ratio, approximately 0:4:30. AC core current characteristics differ from dc.
Mossbauer study of a binary amorphous ferromagnet: Fe80P20
Authors: Musser D. , Chien C. L. , Chen H. S.
Published: February 2003

Binary amorphous Fe80P20 has been studied by 57Fe Mossbauer spectroscopy. The results from this study are compared with those of Fe80B20 so that the influence due to the metalloid elements can be elucidated. The Curie temperature of TC=580 K for Fe80P20 is considerably lower than that of 685 K for Fe80B20. The hyperfine field distribution {P(H) } of Fe80P20 is distinctively asymmetrical as opposed to a nearly symmetrical P(H) in Fe80B20. From the temperature dependence of the hyperfine field and the values of TC we have concluded that both the mean exchange interaction (J0) and the width (ΔJ) of the distribution of exchange interactions {P(J) } are considerably smaller in Fe80P20. A large difference in the isomer shift has also been observed in the two alloys. It is suggested that these large changes are in part caused by the electronic differences of phosphorus and boron. At high temperatures Fe80P20 crystallizes into Fe3P and α-Fe.
Structural instabilities and magnetic properties of amorphous ferromagnets
Authors: Allia P. , Vinai F.
Published: February 2003

A theory is proposed for the temperature dependence of the spontaneous magnetization in amorphous ferromagnets, explicitly considering the effect of large localized fluctuations in exchange integrals due to the motion of some magnetic atoms between neighboring equilibrium positions. These atomic instabilities are related to structural defects characterized by an asymmetric double-well potential, with a wide distribution of energy barriers. The magnetic effects of the local fluctuations are accounted for by means of a mean field theory. The theoretical induced magnetization vs. temperature curves calculated according to this model are found to be in very good agreement with the experimental data relative to several amorphous alloys (Co0.754P0.246; Gd2Co; Fe75P15C10; Fe44Pd36P20; Gd2Au). It is further shown that extrapolation to low temperatures of the barriers number appropriate to describe the magnetization behavior is in good agreement with the corresponding values obtained from the analysis of low-temperature thermal and transport properties of amorphous systems, where phonon assisted tunneling through double-well potential barriers has been invoked.
Hyperfine field distribution at 59Co in amorphous Fe(Co)79P13B8 alloys
Authors: Durand J. , Guerra D. Aliaga , Panissod P. , Hasegawa R.
Published: February 2003

We report the results of 59Co spin-echo measurements at 4.2 °K in amorphous alloys of composition (Fe100−xCox)79P13B8, with x=1, 3, 4, 10, 20, 30, 40, 60, 70, 80, 90 and 100. A comparison is made also with the 59Co NMR spectrum in a-Co3B. Evidence is shown for large quadrupolar effects in the dilute alloys. The influence of short-range order on the hyperfine field distribution in concentrated Co alloys is pointed out.
Abstract: High field magnetoresistance studies in some amorphous metal-metalloid systems
Authors: Rao K. V. , Gudmundsson H. , Anderson A. C. , Chen H. S.
Published: February 2003

We report the first extensive magnetoresistance, (MR), studies on some amorphous transition metal-metalloid systems in applied fields, B, to 22 T and for temperatures above 0.1 K. Specifically, we discuss our results on the alloys (T1−xNix)75(PBAl)25, where T=Fe(Co) and x=0.5(0.8). In both these alloys the observed resistance minimum (at 14 K and 39.8 K resp.) is suppressed (by 3 K and 1.8 K resp.) in B as low as 0.56T. There is a strong T-dependence in the (MR), which can be as large as −0.4%, over a wide temperature range [0.01<T/Tc<3]. Above Tc the curvature of the B dependence of (MR) indicates effects of clustering. At 4K in the Co-Ni alloy we observe a +ve (MR) which after a sharp initial increase remains a constant (+10−5) to B=10T, and then increases linearly at 0.8×10−4/T at higher fields. Such a linear dependence is not observed for the Fe-Ni alloy. Clearly, the magnetic contribution to the T-dependence of the resistivity is indeed significant, and is consistent with the broad distribution of fields in these glassy systems.