bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep center characterization by optically-controlled paramagnetic resonance in AgGaS2
Authors: Von Bardeleben H. J. , Goltzene A. , Schwab C. , Feigelson R. S.
Published: February 2003

A new method for deep center characterization, based on the analysis of their EPR signal intensity under a dual beam optical excitation, is presented. It allows the determination of some important physical parameters of a deep center, like its photoionization energy and its optical capture cross section. An application of this method is given by the study of two transition metal-induced defects in the chalcopyrite compound AgGaS2. The basic interest of this new technique rests in the fact that it yields a quantitative value of parameters useful in deep level theory and that it may help to bridge the gap between physically assessed centers and their chemical identification by regular EPR technique.
High energy electronic Raman scattering in the one-dimensional ferromagnet CsNiF3
Authors: Abdalian A. T. , Moch P. , Cibert J.
Published: February 2003

High energy (6000 to 14000 cm−1) electronic Raman scattering in the one-dimensional ferromagnet CsNiF3 has been studied in the short-range order region above the three dimensional magnetic ordering temperature (2.6 K). Our measurements involve transitions from the 3A2g ground term to the 3T2g and 3T1ga excited terms of the Ni2+ ion 3d8 configuration. Besides broad phonon assisted bands, the spectrum consists of purely electronic sharp lines. The successive moments of the sharp lines depend upon the spin correlation functions, which were experimentally monitored through a temperature or a magnetic field variation. Our experimental results qualitatively agree with the predicted ones.
Covalent magnetism: An alternative to the Stoner model
Authors: Williams A. R. , Zeller R. , Moruzzi V. L. , Gelatt C. D. , Kubler J.
Published: February 2003

We show that itinerant magnetism in a variety of transition-metal systems cannot be described by the familiar Stoner model (rigid-band theory). Magnetism as found in elemental anti-ferromagnets, in certain impurity systems (transition metals in transiton metals), and in certain transition-metal compounds is shown to arise from spin-dependent changes in the covalent interactions between the d states of neighboring transition-metal atoms.
Structural and magnetic properties of Y(Mn1−xFex)12
Authors: Yang Y. C. , Kebe B. , James W. J. , Deportes J. , Yelon W.
Published: February 2003

The crystallographic and the magnetic structures of Y(Mn1−xFex)12 intermetallic compounds were investigated. They crystallize in the ThMn12 structure type. The Y atoms occupy the 2(a) sites and the transition metals are distributed on 3 nonequivalent sites 8i, 8j, and 8f. We have determined the solid solubility limit (x = 0.67) of Fe in YMn12. Neutron diffraction spectra at different temperatures have been used to study the nuclear and magnetic structure of Y(Mn0.7Fe0.3)12 and Y(Mn0.4Fe0.6)12. The Mn and Fe atoms are found to exhibit strong site preference with the i site favoring Mn atoms and the f site Fe atoms. Accordingly the instability of the RFe12 phase can be explained on the basis of the preferential atomic ordering observed in the ternary compounds. Based on the results of magnetic structure refinements using the Rietveld profiling method, antiferromagnetic, noncollinear structures are proposed for these two compounds.
A horizontal monolithic series-array solar battery employing thermomigration
Authors: Norskog A. C. , Warner R. M.
Published: February 2003

By using the thermomigration process of Anthony and Cline (based upon Pfann’s temperature-gradient zone-melting process of the fifties) we have produced parallel aluminum-doped zones extending entirely through an n-type silicon slice of normal thickness. By applying a shallow p-type emitter diffusion to one face and interrupting it within each ’’cell’’ by means of an n+stripe that makes contact to the n-type base of the cell, we have realized a monolithic series-array solar battery, with results that constitute a feasibility demonstration of the method. Its advantages are permitting the entire thickness of the slice to constitute an active region and avoiding more costly dielectric isolation of cells or hand assembly of cells.
Relaxation of local high temperatures due to shock compression as observed by the emf from a copper-Constantan junction
Authors: Kondo Ken-ichi , Sawaoka Akira
Published: February 2003

The anomalous response of a copper-Constantan thermocouple to shock compression, where the junction consists of silver paste and includes a porous layer, is interpreted as being due to local heating and subsequent thermal relaxation by heat conduction. The thermal relaxation pattern, tentatively calculated using the diffusion equation, is consistent with the experimentally observed response.
Behavior of sulfur at high pressures and low temperatures
Authors: Golopentia D. A. , Ruoff A. L.
Published: February 2003

A new type of high-pressure apparatus for low-temperature experiments was built, which allows loading and measuring the load in situ at low temperature (1.5 °K). It uses the diamond anvil in the flat-indentor configuration. It was used to investigate the high-conductivity state of sulfur at low temperatures. For pressures in the 50-GPa range, sulfur is still a semiconductor or at best a two phase semiconductor-metal system. As the temperature is lowered at 50 GPa, the resistance drops slightly, reaches a minimum around 230 °K, and then increases dramatically.
Investigation of a→w transformation in the Zr-Hf system to 42 GPa
Authors: Ming Li-chung , Manghnani Murli H. , Katahara Keith W.
Published: February 2003

Structural transformations in pure Zr and Hf and their alloys with 5.2, 21.1, 42.9, and 71.3 at . % Hf have been investigated up to 42 GPa (1 GPa = 10 kbar) at room temperature (∼22 °C) by in situ high-pressure x-ray diffraction techniques, using a diamond-anvil pressure cell. The pressure of transformation a→w increases rapidly with increasing Hf content. On extrapolation, the pressure of transformation a→w for Hf is estimated to be in the order of 60 GPa. Values of the c0/a0 ratio of the pressure-induced w phase for Zr and its alloys are 0.621±0.002, in good agreement with those of heat-treated w phases in the Zr-Nb system.
Dislocation-free diffusion processes
Authors: Lee Sanboh , Li J. C. M.
Published: February 2003

A diffusion scheme is suggested for charging or discharging solutes into or from a solid in which the surface transport is controlled in such a way that the maximum shear stress at the surface is maintained constant and below the critical shear stress for dislocation generation. Three simple geometries are treated: slab, cylinder, and sphere. It is shown that such a scheme is the fastest diffusion process without plastic yielding anywhere inside the specimen.
Measurement and calculation of Josephson junction device inductances
Authors: Chang W. H.
Published: February 2003

We have measured the inductances of various structures used in Josephson junction devices and circuits by means of a novel differential inductance measurement technique. The structures measured include a single superconductor strip line, multisuperconductor strip lines, a single superconductor strip line crossing a ground plane hole, and two coupled superconductor strip lines crossing a ground plane hole. All measured inductances are compared with inductances calculated from various inductance formulas and two numerical inductance calculation programs. Very good agreements are found between the measured inductances and the calculated results for most cases.
Enhanced elastic moduli in Cu-Ni films with compositional modulation
Authors: Testardi L. R. , Willens R. H. , Krause J. T. , McWhan D. B. , Nakahara S.
Published: February 2003

Films with modulated composition 8-Å Cu/8-Å Ni show an increase in the Young’s and torsional moduli of a factor of 2, relative to bulk or longer-wavelength samples. The film structure is found to be highly textured with coherent lamella for the short-wavelength-enhanced moduli samples, but becomes more random with the probable introduction of misfit dislocations at longer wavelengths. The moduli results support the previous findings of Tsakalakos and Hilliard.
Proximity-effect correction with linear programming
Authors: Carroll Allen M.
Published: February 2003

A new method for computing proximity-effect corrections for submicrometer electron beam lithography is introduced. It is based on a two-parameter resist development model and the restatement of the proximity-effect problem as a linear programming problem. Example solutions in several relevant physical regimes are presented.
Observation of density discontinuities behind reflected shocks close to the transition from regular to Mach reflection
Authors: Walker David K. , Dewey John M. , Scotten Lawrence N.
Published: February 2003

Density discontinuities have been observed behind the reflected shock produced by regular reflection of weak planar shock waves from rigid, smooth surfaces at various angles of incidence. These discontinuities occur behind the point where the incident and reflected shock waves meet and have been seen only for angles of incidence close to those at which transition from regular to Mach reflection takes place. The failure of two-shock theory to predict the angle of transition from regular to Mach reflection for weak shocks may be explained by the experimental observation that near the transition, a simple two-shock picture of the reflection process is not valid.
More about the dielectrophoretic force
Authors: Benguigui L. , Lin I. J.
Published: February 2003

Using the theory of Molinari and Viviani, we show that it is possible to calculate the dielectrophoretic force on a sphere, in almost all the interesting cases. In particular, in an ac field we find that it is necessary to take into account the transient regime.
Photoluminescence dead layer in p-type InP
Authors: Hollingsworth R. E. , Sites J. R.
Published: February 2003

Photoluminescence intensity of p-type InP Schottky diodes was measured as a function of excitation wavelength for several values of applied bias. The intensity increases with penetration depth of the excitation radiation and is quantitatively consistent with a nonradiating surface dead layer. The dead-layer thickness is somewhat less than the diode depletion width, but has the same functional dependence on applied bias.
Optimization of a model external combustion engine
Authors: Band Yehuda B. , Kafri Oded , Salamon Peter
Published: February 2003

Using the Pontryagin maximum principle we optimize the operating conditions of a model external-combustion engine to obtain maximal efficiency. The model engine consists of a cylinder equipped with a piston containing a gas, pumped with a given time-dependent rate of heating, and coupled to a heat bath. We consider a fully cyclic engine, wherein both the volume and the energy of the working fluid are periodic. Such engines possess a finite optimal compression ratio. The gain in efficiency over nonoptimal paths is significant. We demonstrate the results with a numerical example, and we perform a thermodynamic analysis.
GaAs-AlGaAs tunnel junctions for multigap cascade solar cells
Authors: Miller D. L. , Zehr S. W. , Harris J. S.
Published: February 2003

The growth and characterization of tunneling GaAs homojunctions and GaAs-AlGaAs heterojunctions by molecular beam epitaxy for use as optically transparent interconnects in GaAs and AlGaAs solar cells is described. GaAs tunneling interconnects have been achieved with conductances of 300 A/cm2-V at 0.050 V, and p-AlxGa1−x As/n-GaAs heterojunction structures with x up to 0.4 have been grown which have characteristics comparable to GaAs interconnects. Thin interconnects, 1000 Å total thickness, have also been fabricated with conductances comparable to thicker junctions. The effect of dopant diffusion was found to be minimal at the 580 °C junction growth temperature, but annealing these tunnel junctions at 650 °C for several minutes caused diffusion of about 100 Å distance.
The effect of dielectric coatings on charge carrier behavior in liquid crystal cells
Authors: Koezuka H. , Kanegae H. , Ono H. , Shibayama K.
Published: February 2003

Thermal depolarization current (TDC) and dielectric measurements of samples, M-LC-M, M-SiO2-LC-SiO2-M, and M-PI-LC-PI-M [LC = Liquid Crystal, p-C5H11C(O)OC6H4C(O)OC6H4CN-p, PI = polyimide, M = Cr and Al] have been carried out in order to investigate the behavior of charge carriers and the effects of insulating films used as blocking electrodes in liquid crystal cells. Electrode polarizations due to mobile ions contained in LC have been observed for the samples with bare and SiO2-covered electrodes. The blocking ability of the evaporated SiO2 layers exists under ac fields, but decreases with applied dc voltage. The SiO2 has been also indicated to trap the ions formed near the electrode. On the other hand, an interfacial polarization between spin-coated PI and LC has been observed for the samples having polyimide films on the electrodes. The polyimide layers have shown the blocking ability even under dc fields. The behavior of the TDC spectra will also be discussed in detail.
Transient pulse evolution of active mode locking in an intracavity frequency-doubled laser
Authors: Reddy K. P. Jagannatha
Published: February 2003

The theory of transient mode locking for an active modulator in an intracavity frequency-doubled laser is presented. The theory is applied to mode-locked and intracavity frequency-doubled Nd:YAG laser and the mode-locked pulse width is plotted as a function of number of round trips inside the cavity. It is found that the pulse compression is faster and the system takes a very short time to approach the steady state in the presence of a second harmonic generating crystal inside the laser cavity. The effect of modulation depth and the second harmonic conversion efficiency on the temporal behavior of the pulse width is discussed.
X-ray photoemission of carbon: Lineshape analysis and application to studies of coals
Authors: Cheung T. T. P.
Published: February 2003

The singularity index α of the asymmetric C(1s) x-ray photoelectron spectrum (XPS) of vitreous carbon is determined to be 0.19±0.01, independent of the interlayer separation of the graphitic layers. This result is interpreted within the framework of the many-electron theory; two mechanisms are suggested: (1) the modulation of the two-dimensional graphite band structures by the random interlayer perturbation, and (2) the excitonic screening. By assigning the value α=0.19 to be characteristic of carbon atoms associated with polynuclear aromatic rings, we show that the fraction of carbon in these rings in coal can be determined by the asymmetry of the C(1s) XPS line.
Thermal nitridation of silicon dioxide films
Authors: Habraken F. H. P. M. , Kuiper A. E. T. , Tamminga Y. , Theeten J. B.
Published: February 2003

Thermal SiO2 films, ranging in thickness from 200 to 1200 Å, were thermally nitrided using NH3 at temperatures between 800 and 1160 °C and for times varying between 3 min and 5 h. The resulting films were analyzed with Auger electron spectroscopy in combination with argon ion sputtering, Rutherford backscattering spectrometry, spectroscopic ellipsometry, and infrared spectroscopy. The nitridation results in the formation of oxynitride layers in the oxide, the largest nitrogen concentration being found in the surface region and at the SiO2/Si interface. The reaction proceeds via a replacement of oxygen by nitrogen atoms under the action of hydrogen. Although the amount of nitrogen incorporated in the surface region is independent of the original oxide thickness, the interface nitrogen concentration is lower the larger the oxide thickness. This can be explained by assuming that the diffusion of NHx (0<x≤3) through the oxide limits the reaction rate. In the temperature range 1000–1160 °C the rate of the reaction in the surface region is independent of the temperature. During the nitridation reaction the films grow slightly in thickness, due to a further oxidation of the underlying silicon. Only very little nitridation of the substrate is found. The resulting oxide-oxynitride layer structures may be used as oxidation resistance.
Photoelectrochemical properties of n-type NiTiO3
Authors: Salvador P. , Gutiérrez Claudio , Goodenough J. B.
Published: February 2003

The photoelectrochemical behavior of a sintered Nb doped n-NiTiO3 electrode in relation to the photoassisted oxidation of water has been studied. Three bands mediate the different photoprocesses observed: A conduction band (Ti4+:3d) several tenths of one electron volt above the H+/H2 redox level; the O2−:2 p6 band about 3 eV below the conduction band; and the Ni2+:3d8 ‘‘band’’ above the oxygen band that seems just to overlap the O2/H2O level. Electronic transitions induced by UV illumination are mainly O2−→Ti4+ transitions; holes photogenerated in the oxygen band move through this band, by the effect of the internal electric field, to the electrode surface where they react with water molecules with an efficiency similar to that observed in n-TiO2 or SrTiO3. Visible light produces Ni2+→Ti4+ electronic transitions. Hole mobilities in the Ni2+:3d8 ‘‘band’’ appear to be adequate for the photogenerated holes to reach the s.c. surface, where they become trapped at Ni3+ surface centers at an energy level too high to oxidize water efficiently. However, the geometry of the NiTiO3 ilmenite structure makes the oscillator strength for the Ni2+→Ti4+ charge transfer too weak to have an acceptable photoresponse to visible light. Therefore NiTiO3 is not a good candidate for water photoelectrolysis in a photoelectrochemical cell. This conclusion is probably valid for other mixed-metal oxides with ilmenite structure.
Nonlinear anelasticity of magnesium
Authors: Aning Alexander , Suzuki Tetsuro , Wuttig Manfred
Published: February 2003

An approximate solution of the equation of motion of a nonlinear anelastic reed at or near resonance is presented. The steady state solution reproduces the well-known nonlinear resonances. The solution also predicts the existence of automodulations, i.e., self-excited modulations of the amplitude and phase at constant power of excitation of the reed. Numerical examples of such automodulations are presented for an antisymmetric deformation potential. Experimental studies of finite amplitude oscillations of a magnesium reed vibrating at 72 and 431 Hz at room temperature confirm the existence of automodulations. The experimental results can be semiquantitatively described in terms of the solution given. The assumption that finite deformation by twinning represents the essential nonlinearity leads to a self-consistent interpretation. The relaxation time of twinning is obtained from the analysis of the automodulation and is 22 msec in the sample investigated. It is proposed that point defects control the relaxation process.
Polarization of poly(vinylidene fluoride) by application of breakdown fields
Authors: Wang T. T. , West J. E.
Published: February 2003

Films of poly(vinylidene fluoride) have been polarized to a high level of piezoelectric activity by application of high electric fields which would normally cause breakdown in the polymer. The high field poling is accomplished by interposition between the two metal electrodes of a dielectric plate which severely limits the current passing through the polymer film during local discharges. Fields with strengths up to an estimated value of 11 MV/cm were applied to 25-μm-thick biaxially oriented films at room temperature over a period of a few minutes to a few hours without incidence of major breakdowns. The piezoelectric e31 (=e32) coefficient of the poled film increases steadily with the applied field, reaching a value of 32 mC/m2 at the estimated field strength of 11 MV/cm. X-ray and ir analyses of the films before and after poling show that the polarization is accompanied by transformation of the nonpolar α to the polar α phase, and further to the β phase depending on the field strength. However, the α to β conversion is only partially complete even at the highest field used, indicating that further polarization may be achieved with still higher field strengths.
Shielding and generating uniform magnetic fields inside circular and noncircular cross-section dipoles
Authors: Hilal M. A. , Eyssa Y. M.
Published: February 2003

Using toroidal coordinates and Stokes streamline function, field and current distributions can be directly calculated for ring-shaped magnets with general cross section. In this paper, shield surface currents of circular, rectangular, and elliptic cross-section coils are obtained. We also discuss shielding against uniform external field and producing uniform internal fields inside the different cross sections.
The behavior of boron (also arsenic) in bilayers of polycrystalline silicon and tungsten disilicide
Authors: Jahnel F. , Biersack J. , Crowder B. L. , d’Heurle F. M. , Fink D. , Isaac R. D. , Lucchese C. J. , Petersson C. S.
Published: February 2003

Boron doping additions in polysilicon-WSi2 bilayers tend to segregate preferentially in the silicide layer during heat treatments at temperatures between 600 and 1000 °C. This is in contrast to arsenic impurities which under the same conditions diffuse through the silicide and evaporate. The boron analyses were obtained by means of the 10B(n, α) 7Li reaction with thermal neutrons. The arsenic analyses were obtained by means of Rutherford backscattering. The results are compared with results previously obtained from similar samples doped with phosphorous.
Modeling of cw laser annealing of multilayer structures
Authors: Calder I. D. , Sue R.
Published: February 2003

Careful computer modeling can accurately represent the temperature distribution created during laser annealing. In this way a better understanding of the physical processes that contribute to thin film crystallization is achieved, and precise predictions of the effects of various sample geometries on laser annealing are possible. Models of cw laser annealing have always assumed a single homogeneous medium, but practical structures usually consist of several layers of semiconductors, insulators and metals of widely varying thermal and optical properties. This treatment can model an arbitrary number of layers of various thicknesses, each with its characteristic thermal and optical properties. The problem is solved under steady state conditions without phase transitions. A general analytic expression cannot be obtained, but a simple procedure is presented for obtaining the temperature distribution in a given system. Explicit integral expressions are developed for the cases of two and three layers; numerical results are calculated for the Si/glass and Si/SiO2/Si systems.
Random anisotropy effects in amorphous rare earth alloys (invited)
Authors: von Molnar S. , McGuire T. R. , Gambino R. J. , Barbara B.
Published: February 2003

We present specific heat and low field magnetic measurements on amorphous DyCu, DyAu, and DyNi alloy films. The magnetic contribution to the specific heat shows clearly that there are strong crystal fields effects in these systems. The highly anisotropic Dy alloys are compared to Gd alloys with similar exchange interactions but much weaker random anisotropy effects. Magnetic measurements on these two types of amorphous systems in the same field and temperature range show that they have characteristically different behavior. Using Arrot plots of our low field data we find that the Gd alloys all show evidence of spontaneous magnetization below TC. The highly anisotropic Dy alloys do not develop a spontaneous moment at any temperature, a result in agreement with the theory of Aharony and Pytte.
Temperature dependence of the nonlinear susceptibility in spin glasses
Authors: Fähnle M. , Egami T.
Published: February 2003

In most metallic spin glasses the nonlinear susceptibility χ2 =d3M/dH3‖H→0 exhibits a singular behavior at the freezing temperature Tf. Within the framework of the molecular field theory, χ2 is proportional to (T−Tf)−1. However, several experimental results show that χ2 is proportional to (T−Tf)−γs(T) over a wide range of temperature, with temperature dependent values of γs greater than 1. A similar discrepancy is observed for the paramagnetic susceptibility χ0=dM/dH‖H→O of amorphous ferromagnets. We have shown earlier that this anomaly in amorphous ferromagnets results from the noncritical interplay between the magnetic correlations and the spatial fluctuations of the exchange interaction, and it was described by a spatially correlated molecular field theory. We now apply this theory to spin glasses and show that the staggered susceptibility exhibits an anomalous (T−Tf)−γψ(T), (γψ≳1) behaviour in a wide range of temperature, and argue that the nonlinear susceptibility χ2 shows a similar behaviour. We suggest, therefore, that the anomalous behaviour of χ2 does not represent a critical phenomenon, thus the value of γs(T) can be dependent both on the system and temperature.
High magnetic moment in Fe87B11Au2 ribbons
Authors: Severin C. S. , Chen C. W.
Published: February 2003

Amorphous Fe87B11Au2 ribbons that are stable above 300 K displayed saturation magnetization Ms of 223 emu/g at 4.2 K. The deduced average Fe atomic moment μ̄Fe was 2.46 μB, which is relatively high compared to μ̄Fe=2.13 μB in Fe87B13. The higher Fe moment is attributed to a quenched-in, high-volume Fe lattice (similar to that found in amorphous Fe-Au films) stabilized by Au and B atoms. Upon annealing, three crystallization stages were observed. First, a α-Fe phase with about 3 at.% Au emerged at around 620 K followed by a Fe2B phase at ≊745 K. At ≊790 K, a Au-rich phase emerged. There were decreases in Ms (4.2 K) as the isothermal annealing temperature was increased, with the largest decrease coinciding with the precipitation of Fe2B.
NMR and magnetic susceptibility study of the Ca100−xAlx metallic glass system
Authors: Hines W. A. , Miller P. , Paoluzi A. , Tsai C. L. , Giessen B. C.
Published: February 2003

In order to investigate the atomic and electronic structures of the melt spun metallic glass system Ca100−xAlx (15≤x≤45 at. %), measurements of the 27Al NMR Knight shift and linewidth, as well as the magnetic susceptibility, have been carried out at room temperature. Spectra have been obtained for resonance frequencies ranging from 9 to 20 MHz and are characteristic of a convolution of a symmetric nuclear dipole-dipole line and an asymmetric second order quadrupole line. Both the Knight shift and linewidth remain constant throughout the entire glassy regime providing evidence for some form of short range order in this system. An analysis of the magnetic susceptibility results indicates that estimates based on the free electron model are inadequate.
Isotropic behavior of the kinetics of reorientation of induced anisotropy in an amorphous alloy
Authors: Ho Kai-Yuan
Published: February 2003

Using a zero-magnetostriction amorphous alloy, we have shown first, that the kinetics and magnitude of the field-induced anisotropy are independent of the axis of the anisotropy in the plane of a disk sample, and second, that the kinetics of reorientation of the anisotropy from one axis to another at constant temperature are also independent of the axes of the anisotropies. Consideration of the behavior of the vector components of the anisotropy during reorientation suggests that if the observed bulk anisotropy can be regarded as due to the sum of many local anisotropy units, then the reorientation takes place by the decay of one set of anisotropy units and the independent growth of another set.
Theoretical and experimental progress in intermediate valence systems (invited)
Authors: Newns D. M. , Hewson A. C. , Rasul J. W. , Read N.
Published: February 2003

Recent experimental measurements such as susceptibility, specific heat, thermopower, and UPS on a wide range of intermetallic intermediate valence systems, e.g. YbCuAl, CeSn3, support a high degree of universality in the properties of such materials which apparently form a unique class of metallic compounds. The ratio χ(0)/γ≂g2μ2B (J+1) (J+1/2)/π2k2B is a good constant for compounds of a given rare earth (though g and J are rare earth dependent). A class of compounds of a given IV rare earth ion shows scaling of properties in terms of an effective temperature, or energy, scale TF, which is strong function of valence. We review the success of theoretical approaches such as perturbation theory, local Fermi liquid theory, the Bethe Ansatz technique, and large-N perturbation theory in understanding these experimental facts. A challenge continues to be the understanding of the ground state, in which lattice periodicity plays a fundamental role, giving rise to ραT2 in some metallic, and a several meV gap in insulating, IV compounds.
Alternating linear chains in a magnetic field
Authors: Mohan M. , Bonner J. C.
Published: February 2003

The properties of alternating (dimerized) antiferromagnetic Heisenberg chains have become of interest recently, primarily in connection with experimental studies of spin-Peierls systems. In particular, the behavior in an applied magnetic field is largely unexplored. Consequently, a comprehensive theoretical study has been made of the field-dependence of the thermodynamic properties, susceptiblity, and specific heat as a function of temperature of such systems, on the basis of the Bulaevski Hartree-Fock approximation. This study was stimulated by precision susceptibility and specific heat experiments on the spin-Peierls system TTF–AuBDT at the Kamerlingh Onnes Laboratorium, Leiden.
Sn magnetic hyperfine field crossover in the Heusler alloys (Ni1−xPdx)2MnSn
Authors: Mayo W. R. , Dunlap R. A.
Published: February 2003

119Sn Mössbauer effect and bulk magnetization measurements were performed on the series of Heusler alloys (Ni1−xPdx)2MnSn (x=0.0, 0.15, 0.30, 0.40, 0.60, 0.70, 0.85, and 1.0) at 4.2 K. The Sn hyperfine field showed a linear decrease from +94 kOe in Ni2MnSn to −39 kOe in Pd2MnSn. The magnetization measurements gave values of 81 emu/gm in Ni2MnSn and 51 emu/gm in Pd2MnSn and yielded moments of approximately 4 μB per Mn atom in all the alloys in the series. The change in Sn hyperfine field may be explained most simply in terms of a changing conduction electron density which results from changes in the lattice parameter. Theoretical predictions of Jena and Geldart, as well as Blandin and Campbell, are discussed.
Effect of Jahn-Teller distortion on the lattice vibration frequencies of nickel ferrite
Authors: Srivastava C. M. , Srinivasan T. T.
Published: February 2003

The infrared spectra of Ni1−xCuxFe2O4 (x=0, 0.1, 0.2) studied at room temperature in the range of 250–800 cm−1 show two main bands. On adding copper to nickel ferrite, the center frequency of these two bands is found to shift to lower energies. The force constants obtained using the center frequency have been observed to increase linearly with the internuclear separation for both the octahedral and tetrahedral sites.
Mandelstam-Brillouin scattering of light in antiferromagnets (invited)
Authors: Borovik-Romanov A. S. , Kreines N. M.
Published: February 2003

The report reviews experimental investigations on Mandelstam-Brillouin light scattering (MBS) from thermal and excited low energy (1–3 cm−1) quasiparticles (magnons and phonons) in antiferromagnets. Now such investigations have been performed in two rhombohedral antiferromagnets with weak ferromagnetism, FeBO3 and CoCO3. The spin wave spectrum of these substances has a low frequency branch. The MBS experiments allowed to distinguish the contributions in magnon energy from exchange, magnetic, and magnetodipole interactions. Spin wave velocities along trigonal axis and in basal plane of crystals were determined. The second part of the report is devoted to the results of optical experiments on investigation of relaxation processes of magnons with k∼0, excited by antiferromagnetic resonance. The overheating of magnon’s and phonon’s systems in crystal, caused by the so-called ’’bottle neck’’ during relaxation, was discovered. The observation experiments on MBS on parametrically excited magnons and phonons are described in the last part of the report.
Thermal expansion of iron–chromium alloys in the temperature range 4.2–300 K
Authors: Rode V. E. , Lyalin A. I. , Finkelberg S. A.
Published: February 2003

We have studied the thermal expansion coefficient α of the bcc Fe–Cr alloys, Fe65Ni35 alloy and ‘‘nonmagnetic Invar’’ Fe5.53Cr93.93Mn0.54 in the temperature range from 4.2–300 K. The magnetic contribution to α for all investigated alloys is obtained. The magnetic contribution to the thermal expansion of Fe65Ni35 and Fe5.53Cr93.93Mn0.54 alloys is found to be identical. The temperature dependence of the magnetic contribution to α of Fe–Cr alloys for the concentration magnetic transition range is shown to have the same behavior. The model is proposed to explain general features of magnetic contribution to α for investigated alloys.
Texture changes during secondary recrystallization of a high-permeability grain-oriented silicon steel
Authors: Flowers J. W.
Published: February 2003

Primary texture changes during secondary recrystallization were studied for a high-permeability grain-oriented 3% Si–Fe alloy with AlN and MnS as grain-growth inhibitors. Orientation distribution function (ODF) data were obtained at the sheet surface and midplane in the primary recrystallized condition and after several stages of a laboratory-simulated box anneal. In the primary-recrystallized condition, the ideal {554} 〈225̄〉 orientation was the strongest single texture component at both the surface and midplane, and this component was more intense at the surface. During simulated box annealing preferential primary grain growth occured which led to a significant intensification of orientations centered about {554} 〈225̄〉, particularly near the sheet surface. This preferential primary growth can be considered as a competitive process to secondary recrystallization of the cube-on-edge component. Volume fractions of material in regions centered about several ideal orientations were obtained by integration of the ODF, and these data are presented and discussed.
Evolution of research in magnetism in Japan
Authors: Chikazumi S.
Published: February 2003

After describing historical achievements by J. A. Ewing, K. Honda, S. Kaya and their coworkers, important inventions, research, and improvement of various magnetic materials which have been made in Japan are introduced. Then physical studies of various magnetic phenomena, such as domain observations, atomic order and induced anisotropies, the Invar Problems, the low temperature phase of magnetite, and studies related to other magnetic compounds are described. Finally achievements on magnetic theories mainly by T. Nagamiya and his disciples are briefly introduced.
Phase diagram for the In-Ga-P ternary system
Authors: Morrison C. B. , Bedair S. M.
Published: February 2003

Solidus and liquidus data are presented for the 800 °C isotherm of the InxGa1−xP ternary system. The data extend over the region 0.49<x<0.90, and have been developed by growing epitaxial layers of InxGa1−xP on InyGa1−yAs, InP, and GaAs substrates. The simple solution model is used to predict solidus and liquidus isotherms which fit the data.
Determination of the hydrogen diffusion coefficient in hydrogenated amorphous silicon from hydrogen effusion experiments
Authors: Beyer W. , Wagner H.
Published: February 2003

The high-temperature hydrogen evolution process from undoped hydrogenated amorphous silicon (a-Si:H) is known to be diffusion limited. A formula is derived by which the hydrogen diffusion coefficient can be inferred from hydrogen effusion spectra taken at different heating rates or on films of different thickness. Experimental results for glow-discharge a-Si:H films prepared at various laboratories are presented and an excellent agreement to literature data of the hydrogen diffusion coefficient is obtained for undoped and phosphorus-doped samples. For boron-doped films, on the other hand, surface desorption of hydrogen from internal surfaces (voids) is found to be the rate-limiting process for hydrogen evolution.
Electronic effects on the elastic constants of n-type gallium antimonide
Authors: Wong Chuen , Garikepati Poornanandam
Published: February 2003

The second-order elastic stiffness constants of three n-type Te-doped GaSb single crystals were measured by the ultrasonic pulse interference method at 25 °C. Carrier concentrations of the samples are: 1.9×1017, 7.7×1017, and 1.2×1018 per cm3. The largest electronic effect was found in C44: a decrease of 0.32% for the highest doped sample compared with the lowest doped sample. The experimental results were interpreted in terms of Keyes’ theory, which is based on the consideration of electronic free energy. The shear deformation potential Ξ(111)u of the (111) band was found to be 16.5±1.8 eV. The longitudinal deformation potential Ξ(111)d was also estimated.
Reply to ’’Comment on ’Gettering of mobile oxygen and defect stability within back-surface damage regions in Si’ ’’
Authors: Magee T. J. , Furman B. K.
Published: February 2003

It is shown that the macroscopic crack model proposed [H. F. Schaake, J. Appl. Phys. 53, 1224 (1982)] for explaining the enhanced diffusion and redistribution of oxygen is unacceptable and does not constitute an explanation for the long-range (≳120 μm) depletion and diffusion of oxygen occurring at the back surface.
Cell formation and interfacial instability in laser-annealed Si-In and Si-Sb alloys
Authors: Narayan J. , Naramoto H. , White C. W.
Published: February 2003

The formation of cellular structures resulting from interfacial instability has been studied in indium- and antimony-implanted silicon after pulsed ruby laser annealing. The average cell sizes at the onset of instability and in the region of well-developed instability were determined using cross-section and plan-view electron microscopy, while the Rutherford backscattering ion-channeling technique was used to obtain solute concentration profiles. These results on average cell sizes and solute concentrations were compared with the predictions of the perturbation theory, which included the dependence of distribution coefficient on the velocity of solidification.
Millimeter wave mixing with submicron area Nb tunnel junctions
Authors: Callegari A. C. , Buhrman R. A.
Published: February 2003

Submicron area Nb edge tunnel junctions have been fabricated yielding devices with RC times of 10−13 s. Tested as quasiparticle mixers at 55 GHz, they yielded conversion loss of 6.4 db SSB and a noise temperature ?27 K. A gain of 1.4 db with a noise temperature of 145 K was also achieved but was attributed to the Josephson effect.
Replication of bubble states in a (110)-oriented garnet film with orthorhombic anisotropy
Authors: Konishi S. , Sakata T. , Engemann J. , Heidmann J.
Published: February 2003

The replication of two kinds of bubbles found in a (110)-oriented garnet film, large and small elliptical bubbles, was tried by applying a single-chopping pulsed field to the respective stripe domains. The bubbles thus replicated from a seed bubble have the same size, shape, and static bubble collapse field as those of the seed bubble, which means that these two kinds of bubbles are replicated conserving their inherent domain wall structure.
Stress relaxation and its influence on piezoelectric retention characteristics of uniaxially stretched poly(vinylidene fluoride) films
Authors: Wang T. T.
Published: February 2003

Piezoelectic films of uniaxially stretched poly(vinylidene fluoride) were found to exhibit an inverse stress relaxation behavior along the initial draw direction when exposed to elevated temperatures (≳40 °C) under a fixed strain. Further, films aged under a fixed strain were found to display a slower piezoelectric decay than films aged in a stress-free state, especially at high temperatures (e.g., 90 °C). The slower decay in stressed films is believed to be induced by dimensional constraints (rather than by the buildup of film tension) which retard the depolarization by inhibiting molecular relaxation in the films.
A high efficiency HF(H2/F2) chemical laser initiated with a surface-spark ultraviolet flash
Authors: Hokazono Hirokazu , Hishinuma Kazuhiro , Watanabe Kazuhiro , Obara Minoru , Fujioka Tomoo
Published: February 2003

As a novel alternative to the conventional Xe flash lamps, a surface-spark-discharge ultraviolet (UV) flash with a poly-tetra-fluoroethylene (Teflon) resin was utilized to an initiation of a H2/F2 chemical laser. Because we employed a high-voltage and low-inductance power supply to drive a surface-spark flash, a stabilized surface discharge in a high pressure (≃1 atm) laser gas and high efficiency power input to an UV flash have been realized. We have obtained a maximum HF laser output energy of 8.5 J/pulse (14.6 J/ ∂) at an electrical efficiency of 9.7%. A surface-spark light source is experimentally found to be able to uniformly initiate a large-volume laser gas mixture.
A numerical approach to the study of the photomagnetoelectric effect for any injection level
Authors: Augelli V. , Piccolo R. , Rizzo A. , Vasanelli L.
Published: February 2003

The theoretical behavior of both the photomagnetoelectric (PME) effect short-circuit current IPME and the photoconductance ΔG is studied as a function of the light intensity, for any injection level. This is carried out by assuming that in a semiconductor band gap, there are two energy levels which control the recombination kinetics. Also, the dependence of both IPME and ΔG on the light intensity is studied as a function of the illuminated surface recombination velocity.
Experimental search for the first-order phase transition in Fe with H↘ along a [111] direction
Authors: Everett Glen E. , Lin Y. J. , Tung C. J.
Published: February 2003

High-resolution magnetization measurements in Fe single crystal spheres at 4.2 and 1.09 K do not exhibit the predicted first-order phase transition for H↘=H⃗0[111]. Measurements at 0.1° intervals near the expected [111] direction, analyzed to determine the maximum slope δM/δHi, gave no indication of approach to a critical region. The obervation of the transition in DyAl2 and R-E iron garnets but not Fe is not presently understood.
The evidence for a Lifshitz point in MnP (invited)
Authors: Shapira Y.
Published: February 2003

MnP has a triple point where paramagnetic, ferromagnetic, and helicoidal (fan) phases meet. The following features of this point agree with those expected for a Lifshitz point: the order of the various transitions near this point (first or second); the qualitative shapes of the phase boundaries; the crossover exponent φ obtained from the phase boundaries; the variation of the wave vector q↘ in the fan phase; the exponent βk derived from this variation; and dispersion curves for spin waves.
Magnetic surface states studied by angle resolved photoelectron spectroscopy (invited)
Authors: Plummer E. W.
Published: February 2003

Angle resolved photoemission is capable of directly measuring the exchange splitting and dispersion of surface states on single crystals. The spin character of these states must be inferred from knowledge of the spin bands of the solid. The measurements of the bulk band structure using photoemission is not a direct process; therefore a description of the measurement process in the bulk and at the surface is presented. Data for the exchange splitting in the bulk of Fe, Ni, and Co will be discussed and compared to existing data on magnetically split surface states. The temperature dependence of the bulk and surface exchange splitting indicates that the splitting persists above the Curie temperature.
The effect of dilution on magnetic ordering in (TmxY1−x)2(SO4)3⋅8H2O
Authors: Simizu Satoru , Friedberg S. A.
Published: February 2003

The two largest electronic states of Tm3+ in Tm2(SO4)3⋅8H2O are singlets separated by Δ/k?0.88 K. This salt exhibits induced-moment antiferromagnetism below Tc?0.3 K because of interionic coupling 𝒥 (0) which is very close to the critical minimum fraction of Δ. To study the effect on this ordering of a gradual reducton of 𝒥 (0), we have measured the heat capacities of a series of mixed crystals (TmxY1−x)2SO4)3⋅8H2O with x = 0.983, 0.932, 0.865, 0.80, 0.70, and 0.510 as well as the pure salt x = 1 between 0.06 and 0.7 K in a 3He−4He dilution refrigerator. Mean field theory, ignoring nuclear effects, predicts Tc(x) = 0 for x≲0.9. We find, however, that Tc, as measured by the temperature of the Cp maximum, falls rather slowly and nonlinearly with x. The inclusion of hyperfine interaction in the theory partially accounts for the observations, as expected for such a coupled electron-nucleus system, but significant discrepancies remain.
Form factor analysis in rare-earth intermetallics: Evidence for 5d polarization and higher-order exchange terms
Authors: Boucherle J. X. , Schweizer J. , Givord D. , Gregory A. , Schweizer J.
Published: February 2003

The measurement at low temperature of the form factor of rare earth intermetallics allows the determination of both the 4f localized contribution and an additional magnetization density also centered on the rare-earth atoms. This contribution, less localized than that of the 4f electrons, is commonly attributed to conduction electrons. We show that the localization of these electrons is nearly the same in many alloys (RAl2, HoFe2...) and similar to that expected for an atomic 5d shell. In addition, the 4f form factor gives a direct determination of the ground state of the rare-earth ion. This ground state has been proved in several cases (HoAl2, HoFe2, NdCo5...) to be in disagreement with the one deduced from magnetization measurements using crystal-field an molecular-field formalism. Such a disagreement must result from higher-order terms in exchange mechanism.
Pressure dependence of dilute Gd moments in Pr-based ferromagnets
Authors: Hasanain S. K. , Guertin R. P. , Crow J. E. , Teter J. , Foner S.
Published: February 2003

Shender has predicted that in highly enhanced crystalline electric field singlet ground state systems there can be a magnetic polarization in the vicinity of well-localized 4f magnetic ions such as Gd. This is an f-electron analogue of the well-known giant Fe moment in Pd, where d-electrons are involved. A search for such moments in weakly ferromagnetic Pr-based compounds has been undertaken using pressure-dependent magnetization and electrical resistivity ρ. The systems investigated are (1) Gd in Pr3S4 (TC = 2.5 K) and (2) Gd in Pr3Tl (TC = 11 K). For both hosts hydrostatic pressures P<10 kbar cause a transition from ferromagnetism to enhanced paramagnetism. For (Pr0.98Gd0.02)3S4, a spinglass-like transition occurs at 8.5 K. The high field moment shows a large nonlinear decrease with increasing pressure. For Gd in Pr3Tl, TC increases rapidly but nonlinearly with Gd concentration and anomalies are seen in ρ and dρ/dT which are characteristic of ferromagnetic transitions.
Magnetic excitations in HoNi2
Authors: Castets A. , Gignoux D. , Hennion B. , Nicklow R. M.
Published: February 2003

Using inelastic neutron scattering we have studied the magnetic excitations in HoNi2. Several modes have been observed in the [001] direction showing that the magnetic excitations in this compound are governed by crystal field effects. The acoustic mode is the only one which is weakly dispersive. The JHo-Ho interaction deduced is very weak and leads to a calculated Curie temperature much smaller than the experimental one. This shows that although the nickel is not magnetic it could contribute to the magnetic ordering. An analysis of the complete results in terms of crystalline electric field and Heisenberg type exchange interaction fails to account simultaneously for magnetization and inelastic neutron measurement.