bluuebunny/crossref_metadata_2025 huggingface dataset:
Implantation characteristics of InSb
Authors: Pearton S. J. , Nakahara S. , Von Neida A. R. , Short K. T. , Oster L. J.
Published: July 2002

Damage introduction by implantation of Be and Si into InSb, and its removal by rapid thermal annealing in the range 300–400 °C for 20 s was investigated by Rutherford backscattering and transmission electron microscopy. There is good recovery of the lattice upon annealing at 450 °C provided the InSb was not amorphized during the implantation step. At the same time, there is limited redistribution of Be for these annealing conditions, but for Si there is marked diffusion even during a nominal room-temperature implant. Lowering the sample temperature to 77 K during the implant stops this redistribution, with a near-Gaussian ion distribution resulting. The activation of Be is of the order of 50% over the dose range 1013–1015 cm−2. In most cases there is a marked similarity in implant properties of InSb to those of GaSb.
Origin of the supermodulus effect in metallic superlattices
Authors: Wolf D. , Lutsko J. F.
Published: July 2002

We suggest that the maximum in Young’s and the biaxial modulus observed for composition-modulated metallic superlattices arises from the same physical causes as the minimum observed in the shear modulus, namely the mutual attraction between the interfaces. We also suggest that anomalies similar to those in the elastic moduli do not exist in the elastic constants.
A theoretical study of a laser-irradiated capillary discharge
Authors: Petway L. B. , Back C. A. , Estabrook K. , Lee R. W. , Zigler A.
Published: July 2002

A theoretical study of a laser-irradiated capillary discharge is presented. The discharge produces a columnar flow of low-temperature plasma (1 eV) with a density of 1019 atoms/cm3. This ambient low-temperature plasma is then irradiated by a 1.06-μm Nd glass laser with pulse lengths from 100 ps to 1 ns. The resultant plasma is studied, using hydrodynamic simulations coupled to a detailed kinetics model.
Photoluminescence of Cd1−xMnxTe films grown by metalorganic chemical vapor deposition
Authors: Feng Z. C. , Perkowitz S. , Sudharsanan R. , Erbil A. , Pollard K. T. , Rohatgi A. , Bradshaw J. L. , Choyke W. J.
Published: July 2002

Cd1−x Mnx Te (CMT) films grown by metalorganic chemical vapor deposition on GaAs, CdTe/GaAs, and CdS/SnO2 /glass (CSG) have been studied at 2 and 80 K by photoluminescence (PL). Analysis of the CMT bandedge peak yields Mn concentration x and indicates the degree of stress in the films due to lattice mismatch with the substrates, which also causes a blue shift of the PL band with temperature. A CdTe buffer layer greatly reduces stress and resulting defects. PL spectra from polycrystalline CMT films on commercial CSG wafers, reported for the first time, show a strong band near 1.62 eV which may represent states at the CMT-CdS interface. In CMT/CdTe/GaAs, we see evidence of front-to-back inhomogeneity in the CMT film which may appear in layered form.
Preparation and transport properties of high-T
c superconducting thick films
Authors: Aponte J. M. , Octavio M.
Published: July 2002

We have prepared thick films of high Tc superconductors on a variety of substrates: SrTiO3, BeO, Zr(Ca)O2, alumina, and sapphire. The powder of the YBa2Cu3O7−δ compound is mixed with an organic solvent and painted on the substrates. The films are then dried and fired. We have studied the effect of the substrate and of the firing temperature on the superconducting properties of the films. We found an optimum firing temperature of 990 °C. The films prepared are superconducting with Tc (R=0) as high as 82 K. We discuss the shape of the resistance-versus-temperature curves as well as the temperature dependence of the critical currents of these films.
The isolated layer model and transfer impedances for AlxGa1−xAs/GaAs heterostructures
Authors: Li Z.-M. , McAlister S. P. , Hurd C. M.
Published: July 2002

We use the concept of transfer impedances to study a model of Alx Ga1−x As/GaAs heterostructures in which the two-dimensional (2D) gas layer is isolated from the parallel three-dimensional (3D) layer (isolated layer model) but is joined by resistors at the peripheral contacts. We use the conformal mapping method to find the relation between the transfer impedances and the resistivity tensor of the quasi-2D system, and point out differences with the previous literature for a similar model.
Wall charge evolution in discharge tubes
Authors: Curzon F. L.
Published: July 2002

The time evolution of wall charges is treated for a cylindrical discharge tube of radius a, length 2L, and surface resistivity η. Two geometries for the applied field are treated: a field produced by point charges (±Q) at opposite ends of the tube and a uniform transverse field. Both geometries are of use in treating the interactions of discharge tubes in gas discharge display panels. The first field configuration gives rise to wall charge fields which decay with a time scale determined by Lε0η and the wall charges enhance the field strength at the tube center by a factor proportional to (L/a)2 : for transverse fields the corresponding decay time varies as aε0 η. It is pointed out that because of the long decay times, wall charge fields can strongly affect the repetitive switching properties for discharge tubes in gas discharge display panels, even when the repetition rates are only a few kilohertz. The adverse effects of transverse-applied fields can be eliminated by avoiding simultaneous switching of neighboring tubes.
Array modes of multiple-stripe diode lasers: A broad-area mode coupling approach
Authors: Verdiell J. M. , Rajbenbach H. , Huignard J. P.
Published: July 2002

Transverse-mode properties of free-running diode laser arrays are investigated through high-resolution spectrally resolved imaging. Observations are shown not to agree with the supermode theory. The coupling of broad-area modes by gain and temperature perturbations accurately describes the observed modal behavior. Theoretical results presented are in close agreement with the experiments.
Thermomagnetic switching on rare-earth transition-metal alloy magneto-optic disks
Authors: Crasemann J. H. , Hansen P. , Rosenkranz M. , Witter K.
Published: July 2002

The thermomagnetic switching behavior of magneto-optic disks with amorphous TbFeCo and GdTbFe films was investigated on a test recorder. Domain length, write and erase fields, and erase laser power required for total domain erasure was studied for various film compositions, which differ in compensation temperature Tcomp and Curie temperature TC. With increasing TC the domain length at fixed writing laser pulse energy is reduced and the power required to erase domains with a certain size is increased. The optimum external field, for minimal write noise, decreases with increasing TC−Tcomp. The experimental dependencies agree with calculated results obtained from the force balance controlling the domain formation.
Effects of parallel compressions on ring-shaped polycrystalline ferrimagnetic samples
Authors: Le Floc’H M.
Published: July 2002

This work deals with the behavior of the macroscopic magnetic properties of ring-shaped polycrystalline yttrium-iron garnets (YIG) under the action of compressive stresses applied parallel to the measurement direction along the director circles. For this purpose, a high-pressure cell has been designed consisting of a hydrostatic pressure application on the outer side of the ring. The results are separated in two parts according to the sample used: The first one is concerned with YIG samples called ‘‘type D’’ and so defined because of the dispersed nature of their natural domain-wall configuration. The second one is concerned with YIG samples called ‘‘type T’’ and so defined because of the toroidal character of their natural domain-wall configuration. It is shown that the first category (type-D samples) gives results in good agreement with the classical theory of the magnetoelasticity, while the second (type-T samples) gives results altogether inconsistent. The difference of behavior between the two types of samples is explained by the difference between their domain-wall configuration in the spontaneous state. A well-tried theoretical model is used for the general interpretation.
Defect-property correlations in garnet crystals. IV. The optical properties of nickel-doped yttrium aluminum garnet
Authors: Rotman S. R. , Roth M. , Tuller H. L. , Warde C.
Published: July 2002

Nickel-doped yttrium aluminum garnet (Ni:YAG) has an optical absorption spectrum characteristic of Ni+3 located on octahedral sites with an absorption peak at 420 nm. When annealed in reducing atmospheres, the nickel converts to Ni+2 and the 420-nm absorption peak vanishes. Codoping with zirconium fixes the nickel into the Ni+2 state under all annealing conditions. Under these circumstances, some of the nickel is believed to enter the lattice on tetrahedral sites. The characteristic 320-nm defect emission is observed in all crystals.
Distributed feedback guided surface acoustic wave microresonator
Authors: Golan G. , Griffel G. , Seidman A. , Croitoru N.
Published: July 2002

Surface acoustic wave resonators have been used in a number of applications: high-Q frequency filtering, very accurate frequency sources, etc. A major disadvantage of conventional resonators is their large dimensions, which makes them inadequate for integrated acoustics applications. In order to overcome these size limitations a new type of microresonator was designed, developed, and tested. In this paper, theoretical calculations and measurements on two kinds of such devices (a corrugated waveguide filter and a microresonator structure) are presented and their possible applications are discussed.
Evaluation of crystalline quality of heteroepitaxial yttria-stabilized zirconia films on silicon by means of ion beam channeling
Authors: Fukumoto Hirofumi , Imura Takeshi , Osaka Yukio , Nishiyama Fumitaka
Published: July 2002

Yttria-stabilized zirconia (YSZ) films have been deposited by vacuum evaporation on Si(100) substrates heated at 800 °C. Rutherford backscattering spectra of the YSZ films show that they are epitaxially grown on the Si(100) substrate, which is consistent with x-ray diffraction and reflection high-energy electron diffraction observations. The spread of crystallite orientation in the epitaxial film is estimated to be 0.22°, by analyzing the angular dependence of the total backscattering yield. The dominant defect is suggested to be a stacking fault by dechanneling ion energy dependence measurements and 30% of the oxygen atoms are displaced from the oxygen sublattice site.
Steering relativistic electron beams with linear wire arrays
Authors: Humphries S. , Schamiloglu E.
Published: July 2002

Experiments have shown that transverse conducting foils provide strong focusing for high-current relativistic electron beams. We describe a method to focus and to steer such beams using arrays of wires transverse to the direction of beam propagation. In contrast to foils, the wires have high transparency and can steer the beam in a circular accelerator. We present self-consistent equilibrium models for displaced planar beams in a wire array. The models predict the allowed angular divergence and radius of curvature of high-intensity beams. Wire focusing may be useful for compact accelerators. As an example, a 20-MeV beam with current in the range of 10 kA can be guided through an accelerator with a radius of curvature of about 0.5 m.
Collective oscillations of the crystal-field-generated oxygen dipoles as a pairing mechanism in high-T
c superconductor YBa2Cu3O7−δ to explain T
c vs δ
Authors: Sharma R. R. , Lee Heebok
Published: July 2002

A possible pairing mechanism involving the collective oscillations (‘‘dipolons’’) of the crystal-field-generated dipoles of the oxygen ions in the CuO2 planes in the superconductor YBa2Cu3O7−δ has been used to estimate, in the framework of the BCS theory, the variation of Tc as a function of δ, which compares very well with the experimental observations.
Influence of transverse dc self-fields of the electron beam on the dispersion relation in a free-electron laser with an axial magnetic field
Authors: Zhang Shi-chang , Zhang Zhong
Published: July 2002

This paper presents an analytical dispersion equation for a free-electron laser (FEL) with an axial magnetic field, where both the influence of the transverse dc self-fields of the electron beam and the three-dimensional effect of the wiggler are taken into account. Not only FEL mode but also two hybrid modes of FEL with the right- and left-hand circularly polarized cyclotron waves, ω=[k∥+(m−1)kw]v∥+Ω0 and ω=[k∥+(m+1)kw]v∥−Ω0, appear in the dispersion equation. Numerical analysis shows that these self-fields decrease the growth rate of the FEL mode but increase the growth rate of the hybrid mode. Two special cases, a high-current gyrotron (i.e., without a wiggler) and a cyclotron autoresonance maser with a ‘‘phase filter’’ (i.e., with a weak wiggler), are also discussed.
X-ray analysis of lattice imperfections and distortions in a Si/GaP bilayer
Authors: Ishizuka F. , Itoh T.
Published: July 2002

We have investigated the lattice imperfections and the distortions at the interface of a Si/GaP bilayer formed by molecular-beam epitaxy using x-ray diffraction techniques. The lattice imperfections in the GaP substrate and Si epilayer were separately observed by x-ray topography with Berg–Barrett geometry, without the superposition of both layers. Several imperfections having irregular shapes were coincident in both layers, while straight-line imperfections could only be found in the GaP substrates. The origins of these imperfections appeared to be different. The lattice distortions in the bilayer were analyzed by studying the change in the lattice constants of the substrate and the epilayer, using the Bond and double-crystal methods, respectively. The lattice in the substrate was bent with epilayer thickness. The strain in the bilayer and that in the epilayer was caused by different linear thermal expansions and by the difference in lattice constants between Si and GaP, respectively.
Local modification of thin SiO2 films in a scanning tunneling microscope
Authors: Jahanmir J. , West P. E. , Colter P. C.
Published: July 2002

We have used a scanning tunneling microscope to locally modify thin oxide films on silicon. Current-voltage (I-V) measurements were performed on these samples and compared with those on ‘‘as-polished’’ (mechanically and chemically polished by the manufacturer). We found that the I-V measurements on samples with thin oxide films were nearly symmetric, characteristic of metal-oxide-semiconductor structures dominated by interface states. In contrast, we observed band-bending on the ‘‘as-polished’’ samples. The thin oxide film directly under the tip was modified by application of a voltage pulse. This change was reflected in the I-V measurements.
Titanium silicide as a diffusion source for arsenic
Authors: Privitera V. , La Via F. , Rimini E. , Ferla G.
Published: July 2002

The matter transport of arsenic ions implanted into titanium silicide layers has been investigated after thermal diffusion treatment in the 800 °C–1100 °C temperature range. The arsenic atoms redistribute between TiSi2 and Si with a segregation coefficient depending on temperature. The diffused amount increases linearly with the square root of annealing time at 1100 °C. The n-doped shallow Si layer has a quite good electrical activity with a mean resistivity of about 1.2 MΩ cm. The leakage current of the reverse-biased n+/p junction is instead quite high. Stacking faults are observed in the diffused layer.
Fe-Ag multilayers with exceptionally high magnetization and Faraday rotation
Authors: Krishnan R. , Tessier M.
Published: July 2002

Fe/Ag multilayers have been prepared by rf sputtering. Under some conditions of preparation, samples with high magnetization and Faraday rotation are obtained. For example, the magnetization for Fe layers of thickness in the range 2–3 nm is as high as 2.5 T. At an applied field of 1.2 T and at a laser wavelength of 633 nm, for the above samples the Faraday rotation is more than 2 times that of the bulk Fe.
A comparative study of the molecular-beam epitaxial growth of Ag/Fe, Ag/Cr, and Fe/Cr superlattices on GaAs (001)
Authors: Etienne P. , Lequien S. , Nguyen-Van-Dau F. , Cabanel R. , Creuzet G. , Friederich A. , Massies J. , Fert A. , Barthélémy A. , Petroff F.
Published: July 2002

Ag/Fe, Ag/Cr, and Fe/Cr superlattices grown on GaAs (001) by molecular-beam epitaxy are compared on the basis of their structural properties. Highly ordered superlattices with very sharp interfaces are obtained for Ag-based structures (Ag/Fe, Ag/Cr). Although several attempts have been made to improve the growth process of Fe/Cr superlattices, they are far from being so well defined. This is a consequence of a progressive degradation which occurs when the superlattice thickness increases and becomes clearly observable in reflection high-energy electron diffraction above roughly 300 Å. However, using an optimum growth temperature, reasonably well-defined structures, suitable for subsequent magnetic studies, are obtained.
Structure and magnetic properties of single-crystal Fe/Au(100) superlattices synthesized using RHEED oscillation
Authors: Kikuchi H. , Suzuki Y. , Katayama T.
Published: July 2002

Single-crystal bcc-Fe/fcc-Au(100) artificial superlattices have been synthesized by the molecular-beam epitaxy (MBE) method using reflection high-energy electron diffraction (RHEED) intensity oscillation. Magnetic properties of the superlattices consisting of the alternations of about 3.6 ML of Fe and Au layers have been studied. The extrapolated magnetic moment per Fe atom at 0 K is estimated as 2.18±0.10 μB. An enhancement of the Fe moment predicted theoretically has not been observed. The linear temperature dependence of magnetization is observed below 200 K in the Fe/Au superlattices. It turns out that the magnetocrystalline anisotropy (Ku) which points to film normal as an easy axis appears after subtracting the shape anisotropy energy. The magnitude of the Ku corresponds with the value theoretically predicted. Annealing experiments have been also done.
Monte Carlo simulation of the easy-axis antiferromagnetic Heisenberg model on a stacked triangular lattice
Authors: Mailhot A. , Plumer M. L. , Caillé A.
Published: July 2002

Preliminary results are presented of a Monte Carlo simulation to study the easy-axis hexagonal antiferromagnet in a magnetic field applied along the c axis. A wide variety of magnetic phases can be stabilized which are characterized by a period-two modulation along the c axis and a period-three modulation in the basal plane. For sufficiently strong single-ion anisotropy, an Ising-like state is realized where one-third of spins are ferromagnetically coupled between planes and which has an infinitely degenerate ground state.
Correlation of composition and angular uniformity with performance in magneto-optic disks prepared from alloy targets
Authors: Hatwar T. K. , Genova D. , Stinson D. G.
Published: July 2002

Sputtering from an alloy target is the preferred method for the production of magneto-optic recording media. However, when sputtering from an alloy target, the angular dependence of the deposition rate of the rare-earth elements is different from that of the transition-metal elements, causing film composition to vary with position. TbFeCo-based media were deposited on 130-mm-diam glass disks from 2-in.-diam alloy targets, under varying composition and sputtering conditions. Coercivity, Kerr rotation, and reflectivity were measured as a function of position on the disk. Dynamic performance as a function of record power was determined for 1.0-MHz recording at 7 m/s linear velocity (3.5-μm marks). It was found that the angular (in-track) uniformity of the magnetic properties, as well as the average composition and magnetic properties, is correlated to noise level. Systematic variations in the noise level and the carrier-to-noise ratio (CNR) were observed as a function of the film composition. Minimum noise and thus the highest CNR (greater than 60 dB in a 30-kHz-resolution bandwidth) was obtained at a film composition near the compensation point.
Influence on the magnetic properties by the interface reaction between a TbCo thin film and a Si-contained protective layer
Authors: Kim K. C. , Kim J. H. , Moon H. , Seo H. , Hong K. M. , Huh S. Y. , Ahn D. H.
Published: July 2002

Degradation phenomena by interface reaction between TbCo and protective layers (SiNx, AlN) has been investigated. Our study reveals that Co-silicide is formed at the interface and it plays an important role on the degradation process in the TbCo film with SiNx protective layer prepared by dc magnetron reactive sputtering. The possibility of reaction between Co and Si at the interface has been found by using x-ray diffractometry and surface analysis method.
Electronic structure calculations for a rare earth–transition metal amorphous alloy system
Authors: Tanaka Hiroshi , Takayama Shinji
Published: July 2002

In order to clarify the origin of the Kerr effect for a rare earth–transition metal (RE-TM) amorphous alloy system, electronic structure calculations were performed for the first time in an amorphous system including f orbitals. Tb20Fe80 and Nd20Fe80 amorphous alloy compositions were chosen for the present work. The electronic structures were calculated by using the most localized linear muffin-tin orbital method based on atomic sphere approximation and the recursion method. To evaluate the first excited f states of rare-earth metals, it was assumed that the occupied f electrons were sufficiently localized in the inner core of a RE atom to be treated as core electrons. The calculated density of states for a Tb20Fe80 amorphous alloy shows good agreement with reported experimental results measured by x-ray photoelectron spectroscopy (XPS) and inverse XPS. In particular, the unoccupied f-state level and the hybridization property between the Tb d state and the Fe d state were well reproduced. The calculated electronic structure for Nd20Fe80 reveals that the enhancement of the Kerr effect at a light wavelength of around 300 nm in a Nd alloy system originates from the interband transition from d to f state.
Kerr effect enhancement and corrosion resistance improvement by AlN and AlSiN films (abstract)
Authors: Lee Z. Y. , Miao X. S. , Liu X. J. , Lin G. Q. , Wan D. F. , Hu Y. S.
Published: July 2002

RE-TM amorphous thin films with perpendicular magnetic anisotropy are promising for use in erasable optical recording media. In order to improve the drawback of easy oxidation and lower C/N of RE-TM films, some protective layers such as SiO, SiO2, ZnS, AlN, and Si3N4 films were studied.1,2 We have studied the Kerr effect enhancement and corrosion resistance improvement by AlN and AlSiN films. AlN and AlSiN films were prepared on glass, PC, and PMMA substrates by a rf magnetron sputtering system with three targets using low sputtering power. The films have a high refractive index (2–2.15), high optical transparency (over 90%), and high stability. The relation between optical properties and rf reactive sputtering conditions (Ar: N2 ratio, total pressure, sputtering power, sputtering time), composition, spectral transmittance, and uniformity of sputtering AlN and AlSiN films were studied. The Kerr rotation angle was up to 1.5° in AlN/TbFeCo/glass and AlSiN/TbFeCo/glass multilayer structures (laser is incident from air). We also studied AlN/TbFeCo/AlN/glass, AlN/TbFeCo/AlN/Al/glass, AlSiN/TbFeCo/AlSiN/glass and multilayer structure films. The results show that AlN and AlSiN films provide sufficient Kerr effect enhancement and superior corrosion resistance improvement to the RE-TM films. The microstructure of those films were also studied by JEM, XRD, and XPS.
Field-induced microwave absorption in high-T
c superconducting powders: Evidence for a superconducting glass phase at low T
Authors: Gould A. , Bhagat S. M. , Manheimer M. A. , Tyagi S.
Published: July 2002

Measurements of the magnetic-field-induced microwave absorption, P(H), in micron-sized powders of the high-temperature superconductor Y1Ba2Cu3O7 at several microwave frequencies for 1.3 K≤T≤Tc are reported. The hysteresis loops [P(H) vs H] observed at low temperatures (T≤16 K) indicate the presence of spontaneous circulating currents within the sample. These hysteresis loops and dc magnetization data (taken for both field-cooled and zero-field-cooled states) combine to suggest that the magnetic moments of these loops are in a ‘‘spin-glass-like’’ state.
Magnetic properties of Sm-Fe-Ti-Al sputtered films with i
H
c greater than 30 kOe
Authors: Kamprath N. , Qian X. R. , Hegde H. , Cadieu F. J.
Published: July 2002

Recently the synthesis of a new high intrinsic coercive force, iHc=38.5 kOe at 293 K, Sm-Fe-Ti phase in film form was reported. Films with Al additions have now been made, and the preparation conditions are better defined. The addition of 2.3–4.5 at. % Al helped to sharpen the x-ray patterns of the high iHc samples. The iHc values for Al concentrations less than 4 at. % did not fall below 30 kOe for proper preparation conditions. The nominal composition for the high iHc phase samples spanned from 17 to 22 at. % Sm, and Ti/Fe ratios from 0.09 to 0.14 when related to Sm-Ti-Fe. The high iHc samples are reported to be composed of two Ti-substituted phases. The high iHc phase is found to be a SmCo5-related hexagonal structure with a nominal formula of Sm7(Fe,Ti)30. The Ti addition allows Ti to form dumbbell pairs in replacing Sm atoms. The semihard phase component is reported as a cubic Sm(Fe,Ti)2 phase. The iHc values were most sensitive to the Ti/(Ti+Fe) atomic ratio and rose at the rate of +6 kOe/%[Ti/(Ti+Fe)] as the nominal composition of 19 at. % Sm was approached and starts to decrease for higher ratios. Initial magnetization studies have been used to show the influence of the magnetic field that was applied during sputter depositions and crystallization.
Magnetization study on grain-boundary precipitation in a Ni-8 at. % Sn alloy
Authors: Yao Y. D. , Chen Y. Y. , Li T. J. , Chuang T. H.
Published: July 2002

The variations of the grain-boundary precipitates, the electrical resistivity, and the magnetization of a Ni-8 at. % Sn alloy have been investigated as functions of annealing temperature and annealing time. For samples annealed at 773 K, the averaged growth rate of the size of the grain-boundary precipitates is roughly 0.42 μm/h for the first 24 h; the electrical resistivity at T=10 K and the magnetization at T=10 K and H=5 kG vary monotonically with respect to the annealing time for the first 2 weeks, changing from 22.5 to 7 μΩ cm for the electrical resistivity and from 27 to 33 emu/g for the magnetization. A large tail section in the magnetization versus temperature curve was also observed in the aged samples. All these electrical and magnetic variations in the Ni-8 at. % Sn samples annealed at 773 K varied monotonically with respect to the growth of the grain-boundary precipitates.
The behavior of the spontaneous resistive anisotropy near a ferromagnetic and a reentrant transition
Authors: Wang Z. , Kunkel H. P. , Williams Gwyn
Published: July 2002

Measurements of the spontaneous resistive anisotropy (SRA) are presented at 1.5 and 4.2 K on numerous ferromagnetic PdNi alloys and on a reentrant (PdFe)Mn sample. At 1.5 K the SRA in PdNi is shown to exhibit a power-law dependence on reduced composition of the form (1−c/c0)Δ, where c0=2.25(±0.05) at. % Ni is the critical concentration necessary to establish a ferromagnetic ground state, and the exponent Δ is estimated at 2.25(±0.1). In the archetypal reentrant system (Pd99.65Fe0.35)95Mn5 [Tc=9.30(±0.02) K, TSG=4.07 (±0.05)K from ac susceptibility data] the longitudinal and transverse magnetoresistance is strong and negative at both 4.2 and 1.5 K, and as a result the very small SRA is difficult to extract with any precision. Consequently, there is no clear indication from this particular transport coefficient of the transverse freezing predicted to occur at TSG in this system.
Shielded MR head for high-density magnetic recording (invited)
Authors: Maruyama T. , Suzuki T. , Yamada K. , Shimabayashi K. , Tatsumi T. , Motomura Y. , Urai H.
Published: July 2002

A narrow-gap shielded magnetoresistive (MR) head with a 8-μm track width has been constructed for high-density magnetic recording. The head consists of a pair of NiFe shields and a trilayered MR element between the shields. In the MR element NiFe, Ti, and amorphous CoZrMo films are used. The thickness of the three layers and the shields, as well as the shield gap length, are optimized with a one-dimensional self-consistent calculation. The shielded MR head has been fabricated using calculated thickness parameters for individual layers: 60 nm for CoZrMo with 40 nm NiFe and 20 nm Ti, 1-μm shields, and 0.5 μm for the total shield gap. The reproduced characteristics from the MR head are evaluated with a plated disk. Neither Barkhausen noise nor distortion is observed in the output waveform. The output voltage is 600 μVpp at a 4 mA/μm sense current with 30 kFCI transition density. The D50 transition density is 40 kFCI. These values are in good agreement with the calculated values. Assuming a 12-μm track pitch, crosstalk is −29 dB from off-track crosstalk characteristics. This shielded MR head has a potential to achieve high recording density with 40 kBPI and 2000 TPI for small-size disk drives.
Surface properties of magnetic rigid disks for high-density data storage
Authors: Tsai Hsiao-chu , Eltoukhy Atef
Published: July 2002

The chemical toughened glass is shown to be very safe for the disk-drive application based upon Weibull analyses of spin-to-break test data. Investigations revealed that frictional performance of glass disks can be correlated with two parameters (zero crossing and peak to valley) of the surface profile as measured by phase-shift interferometry. To compare the surface characteristics of glass with a conventional Al disk, the piezoelectrical baseline signals were measured by a glide head while flying steadily over a disk without asperity hits. The results showed that the glass disk caused less disturbance to the slider than the Al disk and can thus provide an intrinsically better surface for low-fly-height, high-density application.
High-field magnetostriction of TbCu, DyCu, and HoCu
Authors: Ibarra M. R. , Algarabel P. A. , Pavlovic A. S.
Published: July 2002

Preliminary results are presented on the anisotropic and volume magnetostriction in pulsed high magnetic fields (0–16.6 T) of the antiferromagnetic intermetallics TbCu, DyCu, and HoCu from room temperature to 5 K. The results clearly point out the relevance of these measurements in order to determine magnetic phase transitions induced by the magnetic field. The strain measured was surprisingly large, up to 10−3 for DyCu, which is the largest magnetostriction observed in an antiferromagnet. For TbCu below≊40 K, two distinct field-induced spin-reorientation transitions are exhibited at critical fields of HC1≊2 T and HC2≊8.5 T. This result casts doubt on the collinear nature of the magnetic structure of TbCu. From 50 to 5 K the DyCu results show two anomalies at critical fields HC1≊7.5 T and HC2≊11 T. In addition, these measurements show that at 11 K and below a small anomaly occurs at HC3≊2.5 T. HoCu exhibits a complex magnetostriction behavior, but it too presents definite anomalies at HC1≊2.5 T, HC2≊9 T, and HC3≊13 T. These results would point to a noncollinear magnetic structure for HoCu. All of the critical magnetic field values observed were practically temperature independent.
Formation of high pressure phases in rapidly quenched Fe-Nd alloys
Authors: Liao L. X. , Altounian Z. , Ryan D. H.
Published: July 2002

Fe100−xNdx amorphous ribbons were obtained for compositions with 25<x<50, and partially amorphous ribbons for all other compositions.The amorphous phases were magnetically ordered with Curie temperatures ranging from 421 to 493 K. During crystallization, three metastable phases (M1, M2, and M3) were formed. X-ray structural studies together with Mössbauer and thermomagnetic measurements suggest that the M1 phase is Fe23Nd6 (Mn23Th6 structure) with lattice parameter 1.152 nm and a Curie temperature of 515 K. The M2 phase is identified as Fe2Nd(Cu2Mg structure) with a lattice parameter of 0.745 nm and a Curie temperature of 567 K. The M1 and M2 phases transform to α-Fe and Nd2Fe17 at high temperatures (≥1000 K). The M3 phase is present in the as-quenched ribbons with x≥60 as well as in all crystallized ribbons. Structural data show that it is γ-Nd, an fcc form of Nd. All three nonequilibrium structures are high pressure phases which are often formed during rapid solidification and/or crystallization of amorphous phases.
Low-noise media using double-layer CoNiCr thin films for longitudinal recording
Authors: Hata H. , Fukuichi T. , Yabushita K. , Umesaki M. , Shibata H.
Published: July 2002

A low-noise medium using double-layer CoNiCr thin films for high-density longitudinal magnetic recording has been developed. This medium consists of a Cr underlayer, a first CoNiCr layer, a Cr interlayer, and a second CoNiCr layer. In this study, the effects of Cr interlayer on the magnetic properties and read/write characteristics are investigated. Coercivity increases while remanence thickness product and coercive squareness decrease with increasing Cr interlayer thickness. The media noise is reduced by the presence of the Cr interlayer, and when the sum of the thicknesses of the CoNiCr layers is fixed, the minimum in the media noise and the maximum in the signal-to-noise ratio are obtained in the case when the two CoNiCr layers are of equal thickness. Because of the great reduction in the media noise, we have obtained signal-to-noise ratio of 35.5 dB at 33 kfci, which is greater than that of a single-layer medium by 4 dB. Also, the data suggest that the reduction in the media noise is due to a reduction in the interlayer coupling, by introducing the Cr interlayer, which is accompanied by a reduction in the coercive squareness.
Beta tungsten underlayer for low-noise thin-film longitudinal media
Authors: Ranjan Rajiv
Published: July 2002

This work investigates the magnetic and media noise properties of Co-15 at. % Cr media having β-W underlayer. These results are correlated with the crystallography and the grain structure of the media. Results show that Hc increases with β-W underlayer thickness up to around 100 nm and becomes constant beyond that. The β-W underlayer seems to influence the epitaxial growth of Co (112̄0) and thus has c axis in the plane. Media noise increases with β-W underlayer film thickness. CoCr/β-W media exhibits almost two times lower media noise than a CoCr/Cr media having identical Hc and Brt. The low noise behavior in CoCr/β-W is due to the unique grain structure which reduces the exchange interaction between the CoCr grains.
2D finite-element and analytic calculation of eddy-current losses in thin linear conductors
Authors: Ngnegueu Tr. , Meunier G. , Mailhot M.
Published: July 2002

In many electromagnetic devices, some of the active parts are made of thin conductors (power-transformer windings, high-voltage windings of sheet-winding transformers, etc.). These thin conductors are usually in such a number that taking them individually into account in the mesh-generation procedure for the finite-element analysis would require the solution of too large a system of equations, which may be computer-timing consuming. In this paper, we show that, whether thick conductors are also present or not, the leakage flux can be calculated in dynamic mode as if the regions of thin conductors were made of insulators and, then, eddy-current losses in these conductors can be calculated, using an analytic formula we also provide.
Magnetic structure of {111} stacking faults in nickel
Authors: Chrzan D. C. , Falicov L. M. , MacLaren J. M. , Zhang X.-G. , Gonis A.
Published: July 2002

The magnetic structure of {111} stacking faults in nickel is investigated utilizing a fully self-consistent, layered Korringa–Kohn–Rostoker approach which does not require full three-dimensional symmetry or the use of finite-sized slabs. Localized electronic states appear at the faults. The spin polarization is calculated for a twin boundary, an intrinsic fault, an extrinsic fault, and several other stacking sequences. In all cases, the magnetic moment is found to be insensitive to the orientation of the nearest-neighbor atoms, but instead can be related to the distance to the nearest atom in the direction perpendicular to the fault plane. Very simple empirical expressions for calculating the spin polarization and total energy of any stacking configuration are presented.
Unified description for susceptibility maximum and Curie–Weiss susceptibility on the basis of the Fermi-liquid model (abstract)
Authors: Misawa S.
Published: July 2002

In various paramagnetic and nearly ferromagnetic substances, the phenomenon of the susceptibility maximum at low temperatures is usually accompanied by the Curie–Weiss susceptibility at higher temperatures; the concurrence of these two features is universally observed in 4d and 5d metals, Laves-phase compounds, and heavy-fermion compounds. No existing theories, however, have been able to explain this concurrence. According to the Fermi-liquid model,1,2 we can express the susceptibility, as a matrix form, exactly in terms of the spin-antisymmetric part of the quasiparticle interaction function gij=gεε′ (ε is the quasiparticle energy),  χ(T)∝β 𝒥i 𝒥j (j↓(1/1+2βψ)↓i)[ni (1−ni)]1/2[nj(1−nj)]1/2, (1) where ψij=[ni(1−ni)]1/2 gij[nj(1−nj)]1/2, ni is the Fermi distribution function at state i, and β=1/kT. If gij is given, Eq. (1) can be evaluated numerically. We use the g function, which contains logarithmic terms such as (ε−μ)2 ln‖ε−μ‖ arising from the Fermi-liquid effect (μ is the chemical potential). We find that the calculated result for χ(T) gives a broad maximum at low temperatures because of the logarithmic terms and, at higher temperatures, it follows precisely the Curie–Weiss law, which directly reflects the general form of (1). In conclusion, both the susceptibility maximum and the Curie–Weiss behavior are found to be inherent in any Fermi liquid.
Critical assessment of the physics underlying direct overwrite in magneto-optic recording (invited)
Authors: Lin C.-J.
Published: July 2002

The basic requirements for achieving direct overwrite in magneto-optic recording are discussed from the basic physics of localized magnetization reversal during thermomagnetic recording. The operating principles and the key issues are reviewed and critically assessed for several major direct overwrite approaches including beam modulation using single-layer media, beam modulation using exchange-coupled multilayers, and magnetic field modulation.
Ultrafast thermomagnetic writing processes in rare-earth transition-metal thin films
Authors: Aeschlimann M. , Vaterlaus A. , Lutz M. , Stampanoni M. , Meier F.
Published: July 2002

We use time-resolved spin-polarized photoemission to investigate thermomagnetic writing of domains in magneto-optic media, focusing on the relaxation time of the magnetization and the dynamic behavior of the nucleation process. In our initial studies, we examine a 90-nm-thick GdTbFe film using a pulsed excimer laser (pulse duration: 16 ns) as the light source for the photoemission process. We find that the thermomagnetic switching behavior is different above and below the compensation temperature Tcomp. When the sample temperature is held above Tcomp, the spin polarization of the electrons emitted during the writing pulse has the sign of the initial state even though subsequent examination shows that a reversed magnetization domain has been formed. Therefore, the domain is thermomagnetically nucleated during the trailing edge of the 16 ns writing pulse or even later when the irradiated domain cools down. On the other hand, if the initial temperature is slightly below Tcomp, the electrons emitted during the writing pulse have reversed polarization showing that the reversal of the magnetization takes place quickly compared to the pulse duration. This difference shows that compensation-point writing is much faster than Curie-point writing. Based on these measurements we propose a model to interpret the different thermomagnetic switching processes which take place above and below Tcomp. The results can be explained by different thermal relaxation times between the excited electrons and the lattice and between the electrons and the spin system.
Modeling domain behavior in magneto-optic recording
Authors: Perlov C. M. , Della Torre E. , Birecki H.
Published: July 2002

Two methods of modeling the domain behavior during the magneto-optic write process are reviewed and contrasted. One model divides the medium into discrete cells and attempts to find a domain configuration which minimizes the energy. The second model assumes that the wall is continuous and finds the domain configuration which minimizes the pressure everywhere on the wall. The predictions of the models are compared. An ad hoc model for the nucleation process is also presented.
High lubrication performance of tribologically oriented fluoropolymer molecules analyzed by polarized infrared microspectroscopy
Authors: Sugimoto Iwao , Miyake Shojiro
Published: July 2002

The molecular structural changes induced in sputtered fluoropolymer film by tribological effects is pursued using polarized micro-Fourier-transform-infrared (micro-FTIR) spectroscopy. Hydrogenation of the carbon radicals produced by CF or CC bond cleavage is detected in the mildly rubbed region, together with C■C bond formation. Polarization measurements reveal that a rigid C■C-bond-rich framework is oriented along the sliding direction in a hardly rubbed region. This rigid carbon framework involves CF bonds with low polarizability. This structure greatly contributes to stable lubrication with a low friction coefficient, after the fluctuating lubrication characteristics that occur in the early rubbing stage have stabilized. These molecular structures are decomposed into C 3/4 C and C■C■C bonds through further elimination of CF moieties by abrasive hard rubbing by all means. Finally, they extremely decompose into amorphous carbon and metal carbide under severe conditions involving the reactive metals which appear after the film molecules are worn out.
Photoreflectance measurements on Si δ-doped GaAs samples grown by molecular-beam epitaxy
Authors: Bernussi A. A. , Iikawa F. , Motisuke P. , Basmaji P. , Li M. Siu , Hipolito O.
Published: July 2002

We investigate δ-doped GaAs samples grown by molecular-beam epitaxy with different silicon areal concentration and cap layer thickness, using photoreflectance spectroscopy. The features observed on the high-energy side of the fundamental gap are attributed to transitions involving electronic sub-bands in the δ-doped potential well that take into account the diffusion of the dopants.
Measurement of Hg 6p 3P0,1,2 state densities in the low-pressure positive-column Ar-Hg discharge using 8s 3S1–6p 3P0,1,2 lines
Authors: Lin Tingsheng , Goto Toshio , Arai Toshihiko , Murayama Seiichi
Published: July 2002

The measurement method of Hg 6p 3P0,1,2 state densities using the 8s 3S1–6p 3P0,1,2 lines of less absorption has been developed, and the Hg 6p 3P state densities on the tube axis in the low-pressure positive-column Ar-Hg discharge of 12 mm inner diameter used for the mercury lamp have been measured.
Fluoride dielectric films on InP for metal-insulator-semiconductor applications
Authors: Paul T. K. , Bose D. N.
Published: July 2002

This paper describes the characteristics of thin fluoride films on InP which are used as dielectric for metal-insulator-semiconductor (MIS) devices. Films of Ba1−xSrxF2 (x=0.0, 0.5, 0.83, and 1.0) were deposited by sublimation of mixtures of BaF2 and SrF2 in vacuum under 10−5 Torr pressure. The composition of the films was deduced from x-ray diffraction and energy dispersion analysis by x-ray studies. The electrical activation energies of the films determined between 120 and 300 K were found to be 3.5–22.0×10−3 eV , depending on composition and temperature. The resistivity of the films was in the range of 5.0×1011 to 5.0×1012 Ω cm with the breakdown fields greater than 5.0×105 V cm−1 . The interface state density obtained was as low as 5×1010 cm−2 eV−1 with annealed BaF2 films. Scanning electron microscope studies showed that annealing caused development of cracks resulting in decreased film resistivity. Auger studies gave evidence of broadening of the interface and outdiffusion from the substrate due to annealing.
Lorentz electron microscopy of iron-rare-earth-boron sintered permanent magnets
Authors: Ramesh R. , Thomas G.
Published: July 2002

The interaction of domain walls with microstructural features in sintered Fe-Nd-B magnets has been investigated by Lorentz microscopy using a high-voltage transmission electron microscope. Grain boundaries that are normal to the wall do not affect the progress of a moving wall, while those that are parallel to the wall interact strongly. The effect of the grain boundary Nd-rich fcc phase on the movement of the wall appears to depend upon the thickness of the fcc phase. Inclusions inside the matrix phase that are within 1000 Å interact with the walls to pin them, while larger inclusions do not. It is suggested that a uniform distribution of inclusions with magnetic properties very different from that of the 2-14-1 phase be used to pin domain walls in order to improve the temperature dependence of the intrinsic coercivity and remanence.
Phase modulation in GaAs/AlGaAs double heterostructures. II. Experiment
Authors: Faist J. , Reinhart F.-K.
Published: July 2002

Phase modulation in GaAs/AlxGa1−xAs double heterostructures with different doping profiles is systematically investigated. Very good agreement between the experimental measurements and the theory developed in Part I of this paper is reported. By measuring the phase modulation for both transverse electric and transverse magnetic modes along the [110] and [11̄0] crystallographic directions, we are able to deduce accurate values for the linear electro-optic coefficient. Values of r41=−1.68×10−10 cm/V at λ=1.15 μm and r41=−1.72×10−10 at λ=1.09 μm are obtained with an estimated accuracy of ±5%. An accurate estimation of the carrier effect permits us to deduce the quadratic electro-optic coefficient for GaAs. The values are R11=−2.0×10−16 cm2/V2, R12=−1.7×10−16 cm2/V2 at λ=1.15 μm, and R11=−2.9×10−16 cm2/V2, R12=−2.4×10−16 cm2/V2 at λ=1.09 μm with an estimated uncertainty of ±25% for all values. Contrast measurement of Fabry–Perot fringes enables us to evaluate the modulator losses. A value of 4.8 cm−1 is reported for a P-n doped modulator (n=6×1017 cm−3). Free-carrier absorption is shown to be the dominant loss process in high-quality structures.
Stress development, intermetallic phase formation, and reaction kinetics in Co-Cr and Co-Ti thin films
Authors: Faupel F. , Gupta D. , Agarwala B. N. , Ho P. S.
Published: July 2002

The stress generated during thermal cycling of electron-beam-evaporated Cr-Co and Ti-Co films on quartz substrates was measured by means of the cantilever bending-beam technique between 20 and 550 °C. The thickness ratio was selected to correspond to an atom ratio of [Co]/[Cr] and [Co]/[Ti]>3. In the unreacted films, the residual stress after cycling is tensile and comparable with that in pure Co. In Co-Cr films there is only a slight increase in stress after complete reaction, whereas a marked increase in tensile stress is observed in Co-Ti films. Phase formation and reaction kinetics were investigated by Rutherford backscattering and x-ray diffraction. The dominant phases in Co-Cr are solid solutions of Cr in Co and Co in Cr with the same structure as the original films. In Co-Ti the main reaction product is the intermetallic compound Co3Ti with the Cu3Au structure. The formation of Co3Ti, which is accompanied by volume shrinkage, is diffusion controlled. The high activation energy of 2.4±0.2 eV suggests volume diffusion of Co through the growing phase as a rate limiting process.