bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and electrical properties of a directionally solidified Ge-TiGe2 eutectic
Authors: Ditchek Brian M.
Published: July 2002

Directional solidification of a Ge-TiGe2 eutectic yields an array of aligned TiGe2 fibers in a Ge matrix. These aligned metallic fibers result in a highly anisotropic material such that the ratio of the resistivities perpendicular and parallel to the rods is typically 102–103 at room temperature and even larger at low temperatures. The resistivity of these semiconductor based eutectic composites is examined as a function of the type and concentration of donors. A significant distinction in the resistivity perpendicular to the rods is observed between composites with a p-type and n-type Ge matrix. This difference is analyzed in terms of the depletion layers at the metal-semiconductor junction, as well as the high density of crystalline defects in the Ge created by the two phase solidification and cooling stresses.
Hysteresis free SiO2/InSb metal-insulator-semiconductor diodes
Authors: Okamura Masamichi , Minakata Makoto
Published: July 2002

Hysteresis free capacitance-voltage (C-V) characteristics of SiO2/InSb metal-insulator-semiconductor (MIS) diodes are attained by introducing an in situ Br vapor etching technique into the fabrication process. Interface state density is also reduced by using this technique. It is found that following vapor etching, MIS C-V characteristics are strongly dependent on both the SiO2 film deposition temperature and oxygen flow rate. The optimum condition for SiO2 film deposition to obtain hysteresis free C-V curves and an interface state density of ≤1×1011 cm−2 eV−1 is determined for InSb MIS diodes. The area of the typical optimum conditions for MIS diodes is located in the oxygen flow rate range of 5–6 cc/min and the deposition temperature range of 200–210 °C. The refractive indices of SiO2 films are 1.44–1.45, the breakdown field strengths are more than 2×106 V/cm, and the dielectric constants for 1 MHz are typically 4.7 at 77 K, respectively.
Importance of oxygen-oxygen interactions in silica structures
Authors: Thathachari Y. T. , Tiller W. A.
Published: July 2002

Monte Carlo studies show that an exclusion principle, based upon a minimum allowed O-O separation in adjacent tetrahedra, drastically restricts the relative orientations such tetrahedra can assume. This ad hoc criterion, with no energy considerations involved, reproduces the experimentally observed Si-O-Si angle distribution determined from the structural data of a large number of silicas and silicates. Similar results are obtained when Coulombic or nonbonded energy calculations are used. When extended structures are formed, this steric requirement alone causes additional and severe restrictions on the relative orientations of adjacent tetrahedra. In fact, it is not possible to have completely random orientations of tetrahedra beyond the first neighborhood shell, unless some nonrandomness is introduced to help formation of closed rings. Thus, the completely random continuous network model fails to produce extended structures in vitreous silica and defect models must be introduced to patch up the model. These considerations also apply to GeO2 and SiS2 structures.
Irregularities in helium release rates from metal ditritides
Authors: Mitchell Dean J. , Provo J. Lyn
Published: July 2002

Helium release rates from erbium and zirconium ditritide films were measured with 3-s time resolution. All films exhibited some variability in 3He release rates on this time scale, but the nonuniformity of the release rate was greatest for samples undergoing the transition into accelerated release, which occurs when the occluders approach the maximum quantities of helium that they can retain. The 3He release rate variability appeared to be associated with the spontaneous release of helium in bursts of about 109 atoms. The release of bursts of helium was also stimulated by vibrating or flexing the film substrates. Although these effects are not expected based on the diffusion of isolated helium atoms of the lattice, the effects of temperature on helium release rates were consistent with the diffusion model. These observations lead to the conclusion that two distinct mechanisms are responsible for the release of helium from the metal ditritide films.
Correlation factor for diffusion in an edge dislocation in a simple cubic crystal
Authors: Stark J. P.
Published: July 2002

The correlation factor for diffusion is constructed for a vacancy mechanism of tracer diffusion in an edge dislocation in a simple cubic lattice. The method of calculation evaluates a weak and tight binding approximation to the problem. Comparison of the two approximations suggests that the tight binding approximation may be preferable under all circumstances.
A phenomenological approach to bistable behavior of Josephson junctions
Authors: Nishi Kazuhisa , Nara Shigetoshi , Hamanaka Koichi
Published: July 2002

The interaction of unbiased Josephson junction with external electromagnetic field in the presence of externally applied uniform magnetic field is theoretically examined by means of phenomenological treatment. It is proposed that an irradiated junction with suitably chosen parameters shows a bistable behavior of voltage across the junction as a function of the radiation intensity.
InGaAsP/InP inverted rib waveguide lasers emitting at 1.54 μm
Authors: van der Ziel J. P. , Logan R. A. , Nordland W. A. , Kazarinov R. F.
Published: July 2002

We describe InGaAsP inverted rib waveguide lasers emitting at 1.54 μm with pulsed current thresholds as low as 60 mA, external quantum efficiencies of up to 0.2 per facet, and emitting 16 mW in the lowest order. Pulsed operation to 110 °C with T0 values of 50–72 °C were obtained. For continuous operation at 15 °C up to 21 mW per facet was observed with external quantum efficiencies of 0.15 per facet and T0 up to 62 °C. The maximum continuous operating temperature was 55 °C and was determined by heating of the junction.
TiO2, LiNb3O8, and (TixNb1−x)O2 compound kinetics during Ti:LiNbO3 waveguide fabrication in the presence of water vapors
Authors: De Sario M. , Armenise M. N. , Canali C. , Carnera A. , Mazzoldi P. , Celotti G.
Published: July 2002

The presence of water vapor in the annealing atmosphere during Ti:LiNbO3 optical waveguide fabrication prevents Li out-diffusion, inhibits LiNb3O8 growth, and furthermore decomposes this phase if already formed. As a consequence, the TiO2 and the mixed oxide (TixNb1−x)O2 growth kinetics change. A proton in-diffusion in LiNbO3 with OH− defects and (Li1−yHy)NbO3 molecule formation is suggested to explain these effects and to account for the detected increase of absorbance at 3480 cm−1.
Experimental study of the collective acceleration of deuterons
Authors: Floyd L. E. , Destler W. W.
Published: July 2002

The collective acceleration of deuterons by an intense relativistic electron beam has been studied experimentally. The accelerated ion energy spectra for various different experimental configurations has been measured using stacked foil activation analysis. The spectra extend to energies below the injected electron beam energy, and thus allow estimates of the net efficiency of the acceleration process. The effect of variations in electron beam power and applied magnetic field on the acceleration process are also discussed.
Ion temperature measurement in a plasma column using pulsed CO2 collective scattering and heterodyne detection
Authors: Lachambre J.-L. , Decoste R. , Robert A. , Noël P.
Published: July 2002

We describe a pulsed CO2 laser scattering experiment set up to measure the ion temperature of a magnetically stabilized arc plasma (ne≂1021 m−3, Te≂5 eV). Sensitivity and spectral resolution considerations led us to use heterodyne detection with a separate local oscillator and a multichannel rf frequency analyzer. The forward scattering angle is chosen to be 5° in order to match the expected ion feature spectrum to the receiver bandwidth and also to eliminate spontaneous fluctuations from the small-k larger-amplitude signal. Experimental scattering spectra illustrate the apparatus sensitivity to discharge current and gas mixture. Ion-acoustic resonances are resolved as well as the spectral signatures from various mixed ion species plasmas. The ion temperature appears to be determined to ±10% once Te and ne are known from other measurements. Applications to high temperature fusion plasmas are discussed.
Langmuir probing studies of UV-photoionized CO2 laser mixtures
Authors: Pei-Liang Xie , Yu-Zhi Wang , Feng Yun Wang , Xi-Gang Zhang , Jing-Xing Dong
Published: July 2002

A Langmuir probe incorporated with a boxcar averager is used to measure the temporally and spatially resolved electron density and electron temperature in a UV-photoionization device for several gases and gas mixtures. The predominant ionization mechanism is determined. The data provides information to optimize the effectiveness of the UV preionization operation in high-pressure lasers.
Ion-beam nitriding of steels
Authors: Salik Joshua
Published: July 2002

The application of the ion-beam technique to the nitriding of steels is described. Preliminary results indicate that the technique can be successfully applied for this purpose. Some of the structural changes obtained by this technique are similar to those obtained by ion nitriding. The main difference is the absence of the compound layer and the iron nitrides diffraction lines. The dependence of the resultant microhardness on beam voltage for super nitralloy was found to be different from that of 304 stainless steel.
Phase transformation of Ni2Al3 to NiAl. I. Ion irradiation induced
Authors: Nastasi M. , Hung L. S. , Johnson H. H. , Mayer J. W. , Williams J. M.
Published: July 2002

An ion-irradiation-induced phase transformation from Ni2Al3 to NiAl has been investigated by transmission electron diffraction. Compound samples of Ni2Al3 were irradiated at liquid nitrogen, room temperature, and 100 °C with 300-keV Xe and 60-keV Ne ions. Transformation to NiAl was observed in all cases. Detailed examination of the closely related equilibrium NiAl and Ni2Al3 structures permits explanation of this transformation based on the structural similarity of the two phases and using a model built around radiation disordering of vacancies.
Modeling of high fluence Ti ion implantation and vacuum carburization in steel
Authors: Farkas D. , Singer I. L. , Rangaswamy M.
Published: July 2002

Concentration-versus-depth profiles have been calculated for Ti and C in Ti-implanted 52100 steel. A computer formalism was developed to account for diffusion and mixing processes, as well as sputtering and lattice dilation. A Gaussian distribution of Ti was assumed to be incorporated at each time interval. The effects of sputtering and lattice dilation were then included by means of an appropriate coordinate transformation. C was assumed to be gettered from the vacuum system in a one-to-one ratio with the surface Ti concentration up to a saturation point. Both Ti and C were allowed to diffuse. A series of experimental (Auger) concentration-versus-depth profiles of Ti-implanted steel were analyzed using the above-mentioned assumptions. A best fit procedure for these curves yielded information on the values of the sputtering yield, range, and straggling, as well as the mixing processes that occur during the implantation. The effective diffusivity of Ti was found to be 6×10−15 cm2/sec, a value that is consistent with the cascade mixing mechanism. The effective diffusivity of C was found to be 6×10−15 cm2/sec, and the sputtering yield by Ti atoms was best fit by a value of about 2. The observed range and straggling values were in very good agreement with the values predicted by existing theories, so long as the lattice was allowed to dilate.
Exact one-dimensional pair correlation functions of a monolayer/substrate system
Authors: Pimbley J. M. , Lu T.-M.
Published: July 2002

We have derived an exact expression for the one-dimensional atomic pair correlation function of the combined overlayer and substrate system in the very first stages of epitaxy. The overlayer can have an arbitrary island size distribution. This pair correlation function is then used to evaluate the widths and shapes of low-energy (or high-energy) electron diffraction intensity profiles. Several model calculations have been computed and the diffraction profiles resemble the recent molecular beam epitaxy measurements of Si/Si(111) and W/W(110) systems reported by Henzler and co-workers.
Effect of magnetic-field heat treatment on magnetic properties of rapidly quenched Senperm ribbons (abstract)
Authors: Teshima N. , Narita K. , Yamashiro Y.
Published: July 2002

A hard and brittle Senperm alloy, which is of superior constant permeability, was formed into ribbon shape using a rapid quenching single-roller method. We already reported that the constancy of permeability and mechanical workability were fairly improved on the obtained Senperm ribbon. Yamamoto reported that the constancy of permeability and maximum permeability increased notably and a sharp rectangle hysteresis loop was observed on the alloy after annealing at 750 °C in a magnetic field around 15 Oe. In the present study, the Senperm ribbon was annealed at 900 °C for 7 h in vacuum, followed by reannealing in a magnetic field less than its coercive force. The investigated ribbon has nominal compositions of 16.2 wt. % Ni-10.8 wt. % Si-Fe. The obtained ribbons dimensions are approximately 55 μm thick, 1.5 mm wide and several meters long. The initial permeability and the range of constant permeability after reannealing at 300 °C for 30 min in 0.1-Oe field are slightly improved, whereas they decrease when the reannealing time is lengthened or the magnetic field is increased. The maximum flux density B10 obtained after field reannealing over its Curie point of 548 °C is larger by 5–12% than that obtained prior to reannealing, though it decreases by 10–5% after reannealing at 300 °C. After field reannealing for 10 min at various temperature, the coercive force decreases to one fourth the value obtained prior to field reannealing. An excellent rectangular hysteresis loop is observed on the ribbon annealed at 300 °C for 1 h in a magnetic field of 1.5 Oe. The rectangularity is as much as 98% which is slightly higher than that of Permalloy. The experimental results might indicate the promising usefulness for application of the rapidly quenched Senperm ribbon (e.g., such as high-frequency transformer cores, high-grade magnetic recording head materials, or magnetic amplifier cores).
Concentration dependence of the ordering temperature in magnetic liquids
Authors: Bradbury A. , Menear S. , Chantrell R. W.
Published: July 2002

A Monte Carlo technique is used to predict the influence that magnetic dipolar interations have on thermodynamic ordering in dispersions of fine magnetic particles. The interactions give rise to Curie–Weiss-like behavior with an ordering temperature that is found to vary linearly with particle concentration. The dependence of the ordering temperature on packing fraction is in agreement with predictions from analytical treatments. These observations have important implications in the characterization of magnetic liquids. In particular it confirms that many of the techniques used to calculate particle size distribution parameters will give misleading results unless the measurements are made on very dilute systems.
Study of Voigt-type magneto microwave Kerr effect in ferrites
Authors: Singh Prabhat K. , Singh P. K. , Bakre S. V.
Published: July 2002

The magneto microwave Kerr effect (MMKE) in the Voigt configuration is observed, for the first time, on two polycrystalline MgMn ferrite samples at x-band frequency. The experimental data are analyzed on the basis of the MMKE theory suitably modified for Voigt configuration Kerr effect. The values of effective linewidth have also been calculated.
Domains in constructional steel: Theory and experiment (abstract)
Authors: Szpunar J. A. , Szpunar B.
Published: July 2002

A simple model is suggested which enables the calculation of the relationship between the domain length and the domain wall spacing in constructional steel. The magnetic interaction between domain in neighboring grains is measured from the observed domain patterns, and a coefficient is proposed which makes possible such a calculation for antiparallel domains. The calculated results compare favorably with experiments. However, the observed scatter of experimental results is due to the complex magnetic interaction of ferrite grains with pearlite, cementite and nonmetallic inclusions.
Paramagnetic behavior of R2Fe14B systems (R=Pr, Nd, Dy, or Er)
Authors: Burzo E. , Oswald E. , Huang M. Q. , Boltich E. , Wallace W. E.
Published: July 2002

R2Fe14B compounds, R = Pr, Nd, Dy, or Er, were prepared from high purity rare earths obtained from the Ames Laboratory. The magnetic properties of these and related systems with other rare earths are under investigation in our laboratories. In the present study magnetic susceptibilities were determined from the Curie temperature (TC) (556–596 K) up to a characteristic temperature Tt. Above Tt the susceptibility was observed to increase sharply and to become history-dependent, suggesting sample decomposition or a phase change. Tt = 830, 920, and 960 K for R = Pr, Nd, and Er, respectively. Curie–Weiss behavior is observed for the Pr and Nd compounds but not for Dy2Fe14B and Er2Fe14B. The susceptibility of the latter material follows the hyperbolic form described by Néel, i.e., 1/χ=1/χ0+T/C−σ/(T−θ). For R=Pr and Nd, near TC χ follows the expression χαt−γt=(T−TC)T−1C]. γ=1.37 for R=Pr and 1.41 for R = Nd. The iron paramagnetic moments are 4.02, 4.06, 4.09, and 4.10 μB for Pr2Fe14B and Nd2Fe14B, Dy2Fe14B and Er2Fe14B, respectively, which are close to the value (3.97 μB) obtained for Y2Fe17. The Weiss constants are 575 and 602 K, respectively, for Pr2Fe14B and Nd2Fe14B. Results indicate little itineracy of the 3d electrons in the R2Fe14B systems.
Anomalous magnetic hysteresis in an amorphous Nd54Co36B10 alloy
Authors: Hadjipanayis G. C. , Aly S. H. , Sellmyer D. J.
Published: July 2002

The hysteresis and crystallization behavior of an amorphous Nd54Co36B10 alloy have been examined over a range of temperatures. Crystallization studies show a glass transition temperature around 210 °C, two crystallization peaks at around 220 and 360 °C, and two endothermic peaks at around 530 and 600 °C, respectively. ac susceptibility measurements show an ordering temperature of 38 K for the amorphous phase. Four additional magnetic phases have been observed in the crystallized samples with ordering temperatures 17, 45, 90, and 190 K, respectively. Magnetic measurements on melt-spun ribbons reveal a coercivity of 6 kOe at 4.2 K. The coercivity at 4.2 K of a sample heat treated at the first crystallization temperature is increased to 8 kOe but is reduced gradually upon annealing at higher temperatures and is only 2.5 kOe in a sample annealed at a temperature close to the second endothermic peak.
Temperature and interface effects on the cubic anisotropy of ion-implanted bubble garnets
Authors: Maartense I. , Searle C. W.
Published: July 2002

The effective cubic anisotropy field of garnet films implanted with 100-keV Ne+ ions has been obtained from ac susceptibility measurements. When normalized to the layer’s ordering temperature, the anisotropy field is constant for doses up to 2×1014 Ne+/cm2. An abrupt change in the magnetic state is inferred from the results for higher doses. The measured anisotropies are also strongly affected by the coupling-in of the bulk parameter through exchange at the layer/bulk interface.
Stresses and magnetoelastic anisotropies at implantation edges in ion-implanted garnet films
Authors: Saunders D. A. , Kryder M. H.
Published: July 2002

Stresses at the edge of an ion-implanted region in a magnetic garnet film have been calculated by analogy with thermal-induced stresses in an elastic half space. From these stresses, magnetoelastic anisotropies have been computed for two different implant profiles. Stress calculations show that stress relaxation near an implantation edge decreases with distance from the edge with an exponential decay length of approximately 4t, where t is the implantation layer thickness. Stress perpendicular to the film surface and shearing stress are significant at the implantation edge, but decrease more quickly with decay lengths of approximately 0.8t and 0.6t, respectively. Because of perpendicular and shearing stresses, the anisotropy under the edge of the implantation mask favors planar magnetization. For similar reasons, the anisotropy in the implanted region near the mask edge favors perpendicular magnetization, effectively causing a shift in the mask edge toward the [112̄] direction. The shift is especially evident in materials with λ111≠λ100 and is on the order of 2.5t for a material with λ111=−λ100.
Self-contained measurement of thin-film superconducting penetration depths and nonsuperconducting film thicknesses in Josephson integrated circuits
Authors: Henkels W. H.
Published: July 2002

In measurements of superconducting thin-film penetration depths, the need for a reference penetration depth has been eliminated by a modification of the direct-coupled SQUID technique. Furthermore, the technique is convenient for accurate measurements of insulator and thin-film resistor thicknesses in superconducting integrated circuits. Measurements of the penetration depths and insulator thicknesses have been obtained on different chips from a few wafers of a single fabrication run. The results indicate for the first time, on a small scale, the degree of chip-to-chip and wafer-to-wafer control presently obtainable for these parameters.
Simple generalized oscillator strength density model applied to the simulation of keV electron-energy-loss distributions
Authors: Liljequist D.
Published: July 2002

Monte Carlo calculations of keV electron-energy-loss distributions have been performed using a simple model of the generalized oscillator strength density to simulate inelastic collisions. The model, which rests partly on the use of empirical data (primarily the atomic mean ionization potential) expresses the generalized oscillator strength density as a sum of terms ( j) of the form [ fjδ(W−Wj), QWj] where W is energy transfer, fj and Wj ( j=1,2,3,...) are a sequence of oscillator strengths and resonance energies, respectively, and Q=ℏ2q2/2m, where ℏq is the momentum transfer and m the electron mass. Comparison is made with experimental results reported for 2an transmission through Al, and 7.3-keV internal conversion electrons transmitted through surface layers of Fe.
Oxygen requirement for DF multiple-pulse effect
Authors: Maher W. E. , Hall R. B.
Published: July 2002

Using a high-energy single-pulse DF laser, a multiple-pulse effect (MPE) occurs for aluminum alloys in air. It requires an incident fluence well above the plasma threshold fluence eT. After a number of exposures, the thermally coupled fluence is almost three times the plasma-enhanced value seen for single pulses above eT. The absorptance below eT at 3.8 μm increases by a factor of 5. We now find that the MPE depends on the presence of O2. New experimental data were taken well above eT in air at low pressures and in gas mixtures at 1 atm with varied O2 content. Plasmas were present but the MPE was not for low O2. The normal single-pulse enhancement was absent without O2.
Laser-beam cleaning in a plasma compressor
Authors: Marchand R. , Capjack C. E. , James C. R.
Published: July 2002

The temporal compression of a KrF laser pulse in a plasma cell via Raman backscattering is a promising technique for obtaining pulse widths of relevance to laser-driven fusion. It is shown that this technique can also serve as an effective means for cleaning the spatial modulations in a pump beam. When a spatially incoherent pump is compressed by an initially Gaussian Stokes pulse, the spatial nonuniformities in the pump are averaged out to yield a smooth, nearly Gaussian Stokes pulse. Strong modulations in the pump lead to less overlap with the Stokes pulse, thus indicating a compromise between compression efficiency and the amount of incoherency that can be tolerated in the input pump. It is argued, however, that for compressors operated in the saturated gain limit, with sufficiently long Stokes pulses, considerable beam cleaning can be achieved with little loss of efficiency.
Epitaxy and line tension
Authors: Mederos L. , Quintana A. , Navascués G.
Published: July 2002

The line tension concept is used to generalize the classical theory of heterogeneous nucleation. The theory is applied to study the impingement flux-temperature diagram of nucleation. The epitaxial nucleation zone at the diagram can be drastically modified depending on the sign of the line tension. Line tension also gives place to a new zone of no nucleation due to spreading effects.
Fast radiative processing of platinum silicide
Authors: Van der Spiegel J. , Wei C. S. , Santiago J. J. , Seiberling L. E.
Published: July 2002

High-intensity quartz-halogen tungsten lamps were used to form platinum silicide films. Platinum films of 42 and 52 nm were evaporated on single-crystal silicon and subsequently processed in a roughing vacuum from 5 up to 20 sec. The electrical characteristics and the microstructure of the silicide films were studied by four-point probe measurements, x-ray diffraction, Auger electron spectroscopy, and Rutherford backscattering spectroscopy. The silicide formation started within the first few seconds, and the reaction was essentially completed after 10 sec. The dominant phase was PtSi, while only a small amount of Pt2Si was detected in the 5- and 10-sec processed samples. The presence of oxygen and carbon in the film and processing ambient did not prevent the rapid silicide formation, although it gave rise to a surface layer composed of silicon oxide and other contaminants.
Photoenhanced thermal oxidation of InP
Authors: Fathipour M. , Boyer P. K. , Collins G. J. , Wilmsen C. W.
Published: July 2002

The growth rate of laser-photoenhanced thermally grown native oxides of InP in a N2O ambient and its dependence on growth condition are presented. Increased laser power, substrate temperature, and N2O pressure are observed to increase the growth rate. The topography and the composition of these oxides have been studied, using secondary electron microscopy and x-ray photoemission spectroscopy, respectively. The oxide layers contain In2O3 and a phosphate, probably InPO4. The enhanced growth appears to be caused by both excited oxidizing species and a photon-enhanced surface reaction.
Use of high-field data for determining the Curie temperature
Authors: Aharoni Amikam
Published: July 2002

A modified equation of state is proposed, which allows the use of the Arrott plots at high magnetic fields. The equation is shown to fit rather well the experimental data of Potter on crystalline Fe, and those of Kaul and Rosenberg on amorphous Fe13Ni67B19Si alloy.
Charges in metal-oxide-semiconductor samples of various technologies induced by 6Co-γ- and x-ray quanta
Authors: Ringel H. , Knoll M. , Bräunig D. , Fahrner W. R.
Published: July 2002

Results of x-ray and 60Co-γ irradiations on differently processed metal-oxide-semiconductor (MOS) capacitors are carried out. From experiments at 80 K, the field-dependent charge yield fH(E) and the ionization coefficient K are found. In addition, a simple method is described for calculating the hole trapping factor A. For this purpose, just the measured values of the midgap voltage shifts after irradiation at 80 K and room temperature (RT) are used. The investigations of oxide charge buildup Qfr and interface state generation Dit by x-ray irradiation at RT indicate that samples subject to high-temperature (HT) annealing exhibit a more sensitive interface and a less sensitive bulk of the oxide than those not subject to this step. This is found to be in contrast to results of 60Co-γ irradiations at RT. In this case, samples subject to HT annealing show higher sensitivities of the interface and the oxide bulk than corresponding samples without HT annealing. Independent of technology and oxide thickness, the oxide bulk and the interface are more sensitive to x-ray irradiation than to 60Co-γ irradiation. The dependency of the midgap voltage shift, the interface state density and the hole trapping factor on oxide thickness dox is shown. For both x-ray and 60Co-γ irradiation the same relationships ΔUMG∝dnox; ΔDit∝dn−1ox; A∝dn−2ox (n=2.6) are found (ΔUMG is the midgap voltage shift). Differences between x-ray and 60Co-γ irradiations occur in the coefficients of the ΔUMG, ΔDit, and A vs dox proportionalities.
Contributions of r−1, r−2, r−3 terms of the full dipole fields associated with Raman scattering enhancement from CN molecules adsorbed on a 2-D array of Ag spheroids
Authors: Chu Lan-Chan , Wang Shou-yih
Published: July 2002

The enhancement of Raman scattering from a CN molecule adsorbed on the tip of one of a 2-D array of Ag spheroids has been newly calculated using the full dipole fields. Results are compared to the corresponding experimental data from the lithographically produced Ag microspheroids. While the r−1 term is small in our specific configuration of molecule-spheroids arrangement, the r−2 term of the full dipole fields is found to contribute about the same amount to the excitation profile of the Raman enhancement as the conventional r−3 term. We also find a kind of spectral fluctuation in the Raman excitation profile and have demonstrated it as due to the interference between the r−2 and r−3 fields.
Magnetic behaviors of two spheres which contact each other with an area
Authors: Ishii Y. , Sato M.
Published: July 2002

In the chain of spheres model proposed by Jacobs and Bean, spheres contact each other at a point. In order to see the change of the magnetic behaviors of the chain of spheres when spheres begin to contact each other with an area, we consider the chain of two spheres. Critical field Hcri for the irreversible rotation of the magnetization and coercive force Hc by both the parallel rotation and fanning mechanisms are calculated as a function of the contact area. Uniaxial magnetic anisotropy constant Ku by the parallel rotation mechanism is also calculated as a function of the contact area. Ku, Hcri, and Hc are found to increase, reach a maximum value, and decrease with an increase in contact area. The maximum values of Ku and Hcri by the parallel rotation mechanism are found to be 30% larger than the values of Ku and Hcri for the point contact. The maximum value of Hcri by the fanning mechanism is found to be 15% larger than the value of Hcri for the point contact.
Low-field magnetic hysteresis in gadolinium and terbium
Authors: Wantenaar G. H. J. , Campbell S. J. , Chaplin D. H. , McKenna T. J. , Wilson G. V. H.
Published: July 2002

The Fourier components of the ferromagnetic hysteresis of polycrystalline gadolinium and terbium have been measured in low ac magnetic fields (0.1–15 A m−1) using synchronous detection. The field dependences and magnitudes of the various harmonics cannot be described by the Rayleigh hysteresis law. It is shown that the dominant term in the absorptive component of the first harmonic is associated with a magnetic aftereffect. At the lowest fields (H≲1 A m−1) there are indications that magnetic hysteresis vanishes.
Recent results on hydrogen passivation of silicon sheet solar cells
Authors: Tsuo Y. Simon , Milstein Joseph B.
Published: July 2002

Recent experiments have shown that the fill factor degradation of some hydrogen-passivated dendritic web solar cells we reported earlier [Y. S. Tsuo and J. B. Milstein, Appl. Phys. Lett. 45, 971 (1984)] is caused mainly by thin (less than 7 μm), damaged, front metal grids. A comparison of spectral response data for unpassivated and passivated cells shows that improvements occur mainly in the longer wavelength region, which indicates that bulk properties are enhanced by hydrogen passivation. We have also examined the stability of hydrogen-passivated dendritic web solar cells over a three month period under outdoor test conditions and have not found any degradation. Electron-beam-induced current data have been obtained that show the hydrogen passivation of dislocations as well as grain boundaries in edge-supported-pulling silicon sheet solar cells.
Breakdown voltages of ion-implanted junctions
Authors: Meyers D. C. , Kwong D. L.
Published: July 2002

In this paper an analytic analysis of the breakdown voltage of an ion-implanted junction is presented. A joined half-Gaussian distribution of the implanted ions is used, since it gives better description of the impurity profiles. The results are based on a closed-form solution of Poisson’s equation in the depletion region. Fulop’s average ionization coefficient is used to determine the values for the avalanche breakdown voltage as a function of implantation energy, implant dose, and substrate dopant concentration. The maximum electric field at junction breakdown is also calculated and the results are presented. Finally, the applicability and restrictions of the analysis are discussed.
5
7Fe Mössbauer spectroscopy study of the magnetic properties of R2Fe14B compounds (R=Ce, Nd, Gd, Y)
Authors: van Noort H. M. , de Mooij D. B. , Buschow K. H. J.
Published: July 2002

5 7Fe Mössbauer spectra were taken at 25 and 293 K on four representative specimens of compounds of the series R2Fe14B (R=Ce, Nd, Gd, and Y). In all these cases it proved possible to analyze the spectra in terms of six subspectra associated with the six crystallographically nonequivalent Fe sites in the tetragonal R2Fe14B unit cell. Assuming a linear relation between the observed hyperfine fields and magnetic moments it follows from our analysis that, although the average Fe moment in R2Fe14B is equal to that of α-Fe, there are Fe sites that give rise to moments much higher and much lower than the average value of 2.2 μB/Fe.
A negative transition width in perpendicular recording?
Authors: Yeh N. H.
Published: July 2002

In perpendicular recording, the measured density response curve corrected with gap, spacing, and thickness losses may show a positive slope. This corresponds to an unphysical negative transition width in an arctangent transition. Analysis has been done to understand this phenomenon. We found that for a perpendicular media with Hc much less than 4πMs, an isolated transition is partially demagnetized in the tail region and consists of more high frequency component than an arctangent transition. By linear superposition, the high frequency readback amplitude can be boosted by this enhanced high frequency spectrum in the isolated pulse. The readback resolution of a thick perpendicular media in fact is equivalent to an infinitesimally thin longitudinal media with extremely narrow transition width. However, the readback amplitude is higher due to the thicker magnetic layer. As to a perpendicular media with Hc greater than 4πMs, the so-called ‘‘negative transition width’’ does not occur and the resolution of the readback signal becomes relatively poor.
Microloop measurements of recording head fields versus current
Authors: Hoyt Roger F.
Published: July 2002

Using the microloop technique, measured results are presented for the first time of recording head fields versus current for several thin-film heads. It is found that the field increases linearly with current, becoming nearly constant as the flux density in the head core material reaches the saturation value.
Asymmetric biasing fields from mismatched current-carrying overlay conductors on magnetoresistive replay sensors
Authors: Mapps D. J. , Watson M. L. , Wilton D. T.
Published: July 2002

Magnetoresistive thin-film sensors used in magnetic recording applications are often linearized using a transverse biasing field. For single-domain behavior the biasing field is computed as the average planar value throughout the volume of the sensor element. This paper shows how the correct bias field can be calculated in the general case for a nonmagnetic current-carrying overlay bias conductor not having the same dimensions as the sensor and not symmetrically positioned. This allows the effect of mismatching, for example due to faulty fabrication, to be predicted. The theoretical expressions are confirmed by experiment using a Hall probe. Various graphs are presented which show how the theory can be used in practical cases with typical sensor and conductor dimensions.
Effect of nitrogen on the crystal texture and microstructure of sputtered Ni-Fe films
Authors: Jhingan A. K.
Published: July 2002

This work reports the effect of nitrogen in the sputtering gas on the crystal texture and microstructure of 1 μ thick 81/19 Ni–Fe films sputter deposited on silica glass and silicon. X-ray diffraction, transmission electron microscopy, and scanning auger microprobe analysis have been used to characterize films’ properties. The films show (111) and (002) crystals orientations. Upon increasing the nitrogen content of the sputtering gas, the amount of (111) crystal texture decreases; whereas the amount of (002) crystal texture shows a maxima at about 0.1% nitrogen. The microstructural analysis of films shows that the presence of nitrogen in the sputtering gas promotes fine grain size. The mechanism of crystal texture development with an increase in the amount of nitrogen in the sputtering gas is discussed.
Effect of heat treatment on reactively sputtered iron oxide thin films
Authors: Lin J. K. , Sivertsen J. M. , Judy J. H.
Published: July 2002

A pure Fe target was used to deposit iron oxide thin films by reactive rf sputtering. Both ‘‘regular’’ and ‘‘wet’’ H2 were used as reducing atmospheres to produce Fe3O4. Other parameters such as the nature of the substrate material, substrate table rotation during sputtering, and grain size were studied. The γ-Fe2O3, formed by subsequent oxidation in air at elevated temperatures, can be formed over a wide range of oxidation temperatures using a prior ‘‘wet’’ H2-reduced treatment. A slight increase in grain size was observed as a result of H2 reduction but no alteration of grain size occurred as a result of the subsequent oxidation anneal. Different magnetic properties and vacancy distribution in the spinel lattice were observed for γ-Fe2O3 films deposited on silicon or glass substrates.
Magneto-optical properties of Bi-substituted epitaxial LuSmIG films
Authors: Mada J. , Yamaguchi K.
Published: July 2002

Magneto-optical, compositional, and magnetic properties of Biz(LuSmPb)3−zFe5O12 (z=0.05–0.9) grown epitaxially on Nd3Ga5O12 substrates from melts with different PbO/Bi2O3 ratios were studied. Chemical analysis by an x-ray microanalyzer indicates that Bi is incorporated into these films primarily by replacing Sm. Room-temperature Faraday rotation θF was measured at a wavelength of 633 nm. θF is proportional to Bi concentration z in the film and is −2×104 deg/cm for z=1.0. θF of Ga-substituted films for a Ga concentration of 0.6 was about 20% smaller than that of the unsubstituted film. The magnetic uniaxial anisotropy field Hk measured by a vibrating sample magnetometer ranged from 2500 to 5400 Oe. From the analysis of Hk data, it was found that Pb-Lu and Bi-Lu pairs were major contributors to Hk of the present garnet films.
Magneto-optic properties of Nd-Fe-Co amorphous alloys
Authors: Gambino R. J. , McGuire T. R.
Published: July 2002

The room temperature magneto-optic properties of amorphous alloy films have been studied in the ternary system Ndy(Fe1−xCox)1−y with y=0.2. In the y=0.2 series the Faraday rotation, Kerr rotation, Hall angle, resistivity, and magnetization all increase with x in the Fe-rich compositions. The increase is mainly caused by an increase in the iron moment. The refractive index of the alloys was determined from the Faraday rotation and Hall angle data. The index increases monotonically with total Co atomic fraction indicating a composition dependent band is present.
Characteristics and optimization of reversible optical data storage systems (invited; abstract)
Authors: Bell Alan E.
Published: July 2002

At the present time, the two major approaches to reversible optical data storage are based on either the magneto-optic effect in rare-earth–transition-metal alloys, or on the amorphous-to-crystalline phase transition in a variety of tellurium-based materials. The phase transition approach is attractive because of the relatively large optical read-signal modulation which results. However, careful optimization of these materials is required to satisfy all of the requirements of data retention, fast erasure and a high number of record/erase cycles. The data retention characteristics and cyclability of magneto-optic storage media are not considered to be critical issues. However, the inherently small magnitude of the magneto-optic effect has led, historically, to relatively limited values for playback signal to noise ratio. Antireflective thin-film structures can be used to provide enhancements to the signal to noise ratio of magneto-optic media. The underlying principles and effect of such approaches to the design of magneto-optic media will be reviewed.
Application of high-energy permanent-magnet materials to servomotors
Authors: Semones Burley C.
Published: July 2002

Development of high-energy permanent-magnet materials during the last two decades has provided many opportunities for advancement in servomotor design. The constant interface of magnet producers and users has enhanced the value of the motor product. There are as many grades or classes of servomotors using permanent magnets as there are permanent-magnet types. Each type of servomotor has its own relative class of performance and associated market niche. To look at the overall picture, items such as continuous and peak torque, speed range, weight, strategic material usage, and cost must always be evaluated. Then, various weighting scales can be applied to the different applications. The normalized data will show that higher-energy product magnets offer substantial performance advantages but often cost more than lower-energy product magnets. As a result of NdFeB development, this cost gap is likely to be closed while maintaining the high-performance edge. Considering high-performance market requirements, motors using the new family of materials continue to show the appeal of high-energy motor products. This paper will cover applications of these types of materials and values of products derived. Although some comparison of brush-type motors will be made, most emphasis will be placed on brushless motors. The brushless motors allow full exploitation of material arrangement which will yield optimum results. Future magnet development needs and the resulting trends in servomotor development will be discussed.
Magnetic and Mössbauer studies of electronic interaction between Fe, Fe-Ru alloy clusters on high surface area carbons
Authors: Pannaparayil Thomas , Mulay L. N.
Published: July 2002

In an attempt to make more efficient methanation catalysts, Fe3, and FeRu2 species were dispersed on high surface area (∼l400 m2/g) Cabots CSX-203 carbons. These systems were characterized by magnetization measurements and Mössbauer spectroscopy which indicated the presence of SP (superparamagnetic) γ-Fe2O3 clusters and SP Fe0 clusters in the fresh and reduced states respectively. For the reduced Fe0 clusters the blocking temperature was found to be below 83 K. A relatively large positive isomer shift for the SP Fe0 species showed that electrons from entities such as Ru entered into the d-band of the Fe species, decreasing the S electron density at the 57Fe nucleus. The possibility of metal cluster(s) interaction with the support is being investigated. From magnetic data particle sizes of the SP clusters ranging from 2.0 to 4.2 nm were estimated. For the Fe-Ru2/C system a very low saturation magnetization for Fe0 was observed, further substantiating the possibility that electrons from the Pauli paramagnetic Ru0 entered the d-band of Fe0.
Nonlinear and hysteresis modeling of soft magnetic material for electrical devices
Authors: Chari M. V. K.
Published: July 2002

This paper summarizes two-dimensional nonlinear and hysteresis modeling of electrical devices using soft magnetic materials in their design and assembly. The paper reports on closed-form and numerical methods developed by various researchers in this area.
Magnetostatic wave propagation losses in thorium-substituted YIG
Authors: Halchin D. J. , Stancil D. D. , Gualtieri D. M. , Tumelty P. F.
Published: July 2002

YIG films were grown with thorium added to the melt in varying concentrations with a maximum Th/Y ratio of 0.487. The effect of the addition of thorium on the propagation of magnetostatic forward volume waves at X band was studied using a differential path delay line. It was found that the addition of thorium increased the propagation loss. For Th/Y ratios greater than 0.0428, magnetostatic forward volume waves could not be detected after propagation over a 1-cm path length. Although the variations in thorium content resulted in a range of lattice mismatches including both positive and negative values, there was no observable minimum in the loss corresponding to zero mismatch. It was also observed that the addition of thorium increased the dc conductivity, but calculations showed that the conductivity was not large enough to produce significant eddy current losses. We feel that the addition of thorium increased the amount of Fe2+ present in the films, thus activating the valence-exchange loss mechanism.
Investigation on electron paramagnetic resonance in KMgF3:Cr3+ (abstract)
Authors: Wan Ke-Lin , Zhao Min-Guang , Xiong Quan , Hong Xiao-Yu
Published: July 2002

There have been many measurements appeared from the EPR of 3d ions doped in KMgF3 and in KZnF3. One reason for this interest is realization that these are related to the still imperfectly understood mechanism of superexchange in magnetically ordered compounds. In KMgF3, Mg2+ is in cubic site symmetry. But the EPR measurement shows that the paramagnetic ion is in strong axial environment as it substitutes the site of Mg2+. J. J. Krebs showed that the axial crystal field of Fe3+ in KMgF3:Fe3+ is contributed by both K+ vacancy and the distortion of the nearest-neighbor F− ions. J. L. Patel reported the EPR of Cr3+ doped in KMgF3 and in KZnF3 and estimated the values of Δg=g∥−g⊥, the zero-field splitting D by considering the K+ vacancy. But the calculated value of D (−0.027 cm−1) is far away from the experimental finding (−0.1528 cm−1). In addition, the formula employed by J. L. Patel is a wrong one. In the present work, the values of Δg and D are computed by ab initio calculation. The calculated values (Δg=−0.0006, D=−0.132 cm−1) are in accordance with the experimental findings (Δg=−0.0006, D=−0.1528 cm−1). And the present work predicts that the distortion of the nn F− ions, 3.76° and −0.64° deviating from C3 axis, respectively, are existed, which agrees with the prediction of J. J. Krebs about KMgF3:Fe3+.
Polarized neutron measurement of ‘‘forbidden’’ magnon scattering in Pt3Mn
Authors: Li W-H. , Perry C. H. , Sokoloff J. B. , Lynn J. W. , Nicklow R. M.
Published: July 2002

We have employed inelastic scattering of polarized neutrons to study the nature of the magnetic response in the vicinity of the Curie temperature (TC=493 K) for the intermetallic ferromagnet Pt3Mn. The measurements were taken on the HB-1 triple-axis spectrometer at ORNL, with a field of 10 kOe applied along the scattering vector Q. For 0.9TC <T<1.2TC we observed underdamped magnons not only with the conventional (+) spin-wave polarization but also with the ‘‘forbidden‘‘ (−) polarization, with an intensity difference I(+)−I(−) which is approximately proportional to the magnetization. Both these observations are in agreement with the slowly fluctuating spin-density theory of itinerant ferromagnetism.