bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of atomic mass of underlayer material in the transition noise of longitudinal media
Authors: Yogi Tadashi , Nguyen Thao , Lambert Steven E. , Gorman Grace L. , Kakalec Michael A. , Castillo Gil
Published: July 2002

Magnetic and recording properties of CoPtCr on Mo and W underlayers were investigated and compared to Cr underlayers over the sputtering pressure range of 3–24 mTorr. Normalized media transition noise decreases with increasing pressure in all cases, and the reduction can be attributed to a reduced intergrain exchange coupling due to isolation of the magnetic grains. In the low-pressure regime, the transition noise increases with increasing atomic mass of the underlayer, Cr<Mo<W. This trend can be attributed to the growth features of the underlayers which change from a partially coupled structure for Cr to closely coupled grains for W. We attribute this behavior in the low-pressure regime to increasing mobility with increasing atomic mass since the energy flux of the sputtered atoms and the backreflected argon atoms increases with the atomic mass of the target. In the high-pressure regime, all underlayers produce an isolated grain morphology in the magnetic layer, which indicates sufficient thermalization of the atoms during the transport, resulting in similarly low values of transition noise.
Fluorine-enhanced nitridation of silicon at low temperatures in a microwave plasma
Authors: Ray S. K. , Maiti C. K. , Chakrabarti N. B.
Published: July 2002

A microwave plasma discharge at very low temperatures (200–250 °C) has been used for the growth of thin silicon oxynitride films suitable for gate dielectric applications. The addition of CHF3 as a source of fluorine enhances the growth rate. A x-ray photoelectron spectroscopy study indicates the incorporation of fluorine (F/Si≂0.2) in the film. Electrical properties of the grown layers have been evaluated by the characterization of metal-insulator-semiconductor capacitors. Results have indicated the presence of negative charges in the insulator. The estimated charge density is lowest for the fluorinated film. The conduction mechanism in the films at room temperature appears to be Frenkel–Poole type.
The influence of thermal treatment on the elastic-plastic properties of the metallic glass surface
Authors: Novikov V. N.
Published: July 2002

Experimental studies were conducted on the elastic-plastic deformation of the surface and inner layers of the metallic glass (MG) Co77Fe4Cr7Si8B4 ribbon using the indentation method. It was established that the elastic-plastic properties of the surface and inner layers of the amorphous samples differ considerably. Elastic recovery of the hardness indentation in the surface layers of the amorphous alloy does not exist within the limits of the experimental error (at the depth of deformation up to 0.7 μm) and it gradually increases with increase of the depth of indentation. The effect of the ‘‘advantageous’’ plasticity (or ‘‘superplasticity’’) of the surface layers is observed only in as-quenched MG samples with a low concentration of crystallization centers. An increase in the volume of the crystalline phases in the amorphous matrix, when annealed in the temperature range characteristic of the process of structural relaxation, results in the appearance and considerable growth of the elastic recovery of the hardness indentation in the surface layers of the MG ribbon.
Temperature dependence of carrier density in depleted epitaxial layers deposited on semi-insulating substrates
Authors: Weiser K. , Solomon P. M. , Wright S. L. , Parker B.
Published: July 2002

We have calculated the temperature dependence of the carrier density in epitaxial layers of semiconductors deposited on semi-insulating substrates when the potentials at the surface and the substrate interface are pinned. The results of these calculations are compared to experiments on thin, nominally undoped p-type layers of GaAs deposited epitaxially on EL2-dominated substrates. The theory predicts that as the temperature is lowered to some critical value the depletion layers at the edges of the epilayer overlap for thin, lightly doped samples. Below this value the carrier density decreases exponentially with inverse temperature with an activation energy which depends on the surface and interface potentials, as well as on the dopant concentration and the width of the layer. This activation energy can be derived analytically for strong depletion. In the intermediate range between negligible and complete depletion of the layer the carrier density must be obtained by numerical methods, and we present the results of such a calculation.
High-rate (∼50-Å/s) deposition of ZnO films for amorphous silicon alloy solar-cell back-reflector application
Authors: Banerjee A. , Wolf D. , Yang J. , Guha S.
Published: July 2002

Back reflectors have been fabricated by the deposition of ZnO films on textured Ag films. High deposition rates of ∼50 Å/s have been achieved by the dc magnetron sputtering technique. The ZnO target used has been prepared in our laboratory. Amorphous silicon alloy solar cells have been deposited on the ZnO/textured Ag back reflector. Control samples have been prepared by the deposition of identical cells on the same back reflector, but in which the ZnO films have been prepared by a low-rate ∼5-Å/s rf sputtering process. The short-circuit current density, which has been used as the primary test parameter for evaluating the back reflectors, is slightly superior in the case of the high-rate ZnO back reflector. The high-rate deposition process is, therefore, attractive for large-volume production application.
Moderate-temperature anneal of 7-nm thermal SiO2 in O2- and H2O-free atmosphere: Effects on Si-SiO2 interface-trap distribution
Authors: Dori L. , Stathis J. H. , Tornello J. A.
Published: July 2002

A silicide anneal furnace, nominally oxygen and water free, has been used to anneal in the temperature range between 500 and 800 °C, in Ar or N2, silicon/oxide structures having a dielectric layer (thermal SiO2) about 7 nm thick. Quasistatic current-voltage measurements have pointed out a dramatic increase of the interface traps after just a few minutes anneal at T=700 °C. To prove that such an increase on interface-trap concentration could be correlated to a very low oxygen and/or water content inside the anneal chamber, the same oxide films have been annealed, before metal deposition, under ultrahigh vacuum (UHV)(10−8 Torr) in the same temperature range and for the same time intervals. Electron paramagnetic resonance (EPR) analysis has shown an increase of the Pb(111) and Pb1(100) defect centers, leaving unchanged the density of Pb0(100) defect centers. Experimental data on annealing efficiency and the strong similarity observed between results after anneals performed in the silicide anneal furnace and under UHV lend support to the idea that the cause of the Si-SiO2 interface degradation may be the Pb center reverse-passivation reaction. Also, EPR analysis has provided evidence of a different annihilation behavior of the Pb(111) and Pb0(100) centers. Finally, the comparison between the time-zero breakdown distribution after anneal in a silicide anneal furnace and under UHV has shown that (i) the Si-SiO2 interface degradation is not a precursor step of a more complex reaction process leading to the loss of the oxide integrity; (ii) for a thin oxide layer (in our case less than 10 nm), the electrical activation of macroscopic defects during anneal under vacuum happens at temperature much lower than previously reported.
A computer simulation of stripe deterioration through electromigration
Authors: Huntington H. B. , Kalukin A. , Meng P. P. , Shy Y. T. , Ahmad S.
Published: July 2002

A computer simulation of stripe deterioration under electromigration is developed with especial regard to the physical aspects of the process. A grain-boundary network is first established appropriate to a {111} grain-boundary texture by a Voronoi process. Stress relief through the motion of network vertices can be used to simulate the effects of annealing. In operation, two different situations are considered: (1) free-surface condition and (2) operation under a passivating surface containment. With the free-surface condition, voids grow internally while the extra material spreads over the surface. With the passivating condition, the matter is conserved and eventually a steady state ensues. The possibility of sideways extrusions or ‘‘spikes’’ is considered. Many other possible applications of the model are indicated.
Effect of superfluorescent emission on the operation of an optically pumped CF4 laser
Authors: Sinha Sucharita
Published: July 2002

A theoretical study investigating the effect of superfluorescent emission on the operation of an optically pumped CF4 laser is reported. The coupled space- and time-dependent rate equations for the molecular population densities and the photon fluxes have been numerically solved to study the dependence of the superfluorescent emission contents in the CF4-laser output on the various laser parameters such as the temperature, pressure, pumping rate, and the feedback factors. We have studied the effect of the temporal shape of the CO2 pump pulse on the superfluorescent emission and the laser-pulse energies. Our calculations indicate that a considerable reduction in the superfluorescent emission is possible by shaping the pump CO2-laser pulse and by choosing the laser operating parameters appropriately. We have also investigated the effect of the addition of buffer gas on the superfluorescent emission and laser emission.
Growth and characterization of high-quality In0.32Ga0.68P layers on GaAs0.61P0.39 substrates by liquid-phase epitaxy
Authors: Wu Meng-Chyi , Chen Chyuan-Wei , Lu Shoei-Chyuan
Published: July 2002

High-quality In1−xGaxP epitaxial layers were grown on GaAs0.61P0.39 substrates by liquid-phase epitaxy using a supercooling technique. The growth conditions and properties of the undoped In1−xGaxP layers are described in detail. The lattice mismatch normal to the wafer surface between the In1−xGaxP layer and GaAs0.61P0.39 substrate varies linearly with the supercooled temperature of the growth solution. Low-carrier-concentration undoped epitaxial layers can be grown from an In solution baked at temperature higher than 900 °C for 10 h and with a suitable supersaturation temperature. The lowest carrier concentrations of 8–20×1015 cm−3 measured by the capacitance-voltage method have been achieved in the layers grown with a 9–12 °C supercooled temperature. These samples with a lattice mismatch of ∼+0.15% also show the narrowest full widths at half maximum of photoluminescence peaks of 36 meV at 300 K, 11.5 meV at 16 K, and 7.5 meV at 4.5 K. The electrical and optical properties of the In1−xGaxP epitaxial layers are better than those reported previously. From the above results, the optimum growth condition could then be determined.
Random errors in iron-dominated microundulators
Authors: Gallardo Juan C.
Published: July 2002

We describe a mathematical model of errors in iron-dominated microundulators introduced by manufacturing (machining) tolerances of the pole pieces. Explicit expressions for the perturbation fields are derived. We use these fields in a simulation, to calculate the first, second, and phase integrals describing the effects on the electron trajectory in the wiggler.
Efficient solutions for scattering from strips and slots in the presence of a dielectric half-space: Extension to wide scatterers. II. Applications
Authors: Tsalamengas John L. , Fikioris John G.
Published: July 2002

TE/TM scattering by strips and slots in the presence of different media can be conveniently formulated in terms of four distinct types of singular integral and integro-differential equations of the first kind. These equations are amenable to an analytical and numerically very efficient and stable solution by the methods proposed in part I [J. Appl. Phys. 70, 1121 (1990)] for scatterers ranging from very narrow to very wide ones. Part II presents specific applications of the above algorithms along with further numerical results. Examples include characteristic currents on a slot separating two isotropic/uniaxially anisotropic half-spaces, characteristic currents on a strip right on the interface between two dielectric half-spaces, TM scattering by a strip right on the planar boundary separating two air/ferrite half-spaces, and TE scattering by a strip on the interface between two dielectric half-spaces.
Comment on ‘‘A contribution to the theory of beam-induced current characterization of dislocations’’ [J. Appl. Phys. 69, 6387 (1991)]
Authors: Donolato C.
Published: July 2002

Pasemann [J. Appl. Phys. 69, 6387 (1991)] has recently compared exact and first-order calculations of the charge collection contrast of a straight dislocation perpendicular to the surface of a semiconductor, finding substantially different dependence on the beam energy at low beam energies. Here it is shown that Pasemann’s result is only a consequence of having used finite values of the dislocation radius in the exact evaluations and zero in the approximate ones. For nonvanishing dislocation radius, the first-order approximation reproduces the exact contrast trend at any beam energy.
Interdiffusion and morphology variation of thin Y–Ba–Cu–O films deposited on MgO substrates during annealing
Authors: Igarashi Y. , Fujino Y.
Published: July 2002

For the purpose of investigating the interdiffusion properties between thin Y–Ba–Cu–O films of compositions near YBa2Cu3O7−y and MgO substrates, time evolution of both Rutherford backscattering spectra and scanning electron microscope images during annealing were observed. Actual diffusivities of Y, Ba, and Cu elements in the MgO substrates have been found to be extremely smaller than the values previously reported. The origins of the discrepancies between the present and the previously reported results are discussed in connection with the morphology variation of the thin Y–Ba–Cu–O films on the MgO substrates during heat treatments.
Transient behavior of boron diffusion coefficient in silicon in oxidizing ambient and extrinsic conditions: Influence of point defect recombination
Authors: Tsoukalas Dimitris
Published: July 2002

We present experimental results that show the variation of the diffusion coefficient of boron in silicon as a function of the oxidation time in extrinsic conditions. A model is then developed that explains quite satisfactorily this experimentally detected dependence. The model assumes that recombination between self-interstitials and vacancies takes place reducing their number and consequently their contribution to the diffusion of boron. Our results show that this method can fit experimental data using only the interstitialcy diffusion component as a parameter. The best fitting is obtained when fI equals 0.4.
In situ stress measurements of gold films on glass substrates during thermal cycling
Authors: Katz A. , Nakahara S. , Geva M.
Published: July 2002

The stress of thin (100 nm) gold films grown by electron-beam deposition onto cover-glass substrates was measured dynamically during heating and cooling cycles between room temperature and 500 °C. The initial tensile stress, 82 MPa of the as-deposited films increased slowly with temperature up to about 300 MPa at 375 °C, and then decreased to 120 MPa on further heating to 500 °C. When the film was cooled from 500 °C back to room temperature, the final film stress became compressive (−50 MPa). A transmission electron microscope study has shown that when the temperature is raised above ∼370 °C, which is the eutectic temperature of the gold–silicon binary alloy, an interfacial reaction started between the gold film and the glass substrate. This interfacial reaction can account for the stress relaxation occurring at the high temperatures.
The proton stopping power of aluminum and nickel ions
Authors: McGuire E. J.
Published: July 2002

Results are presented for the stopping power for protons of 1–100 MeV energy by Ni+n ions with 0≤n≤26. Older Al stopping power results are re-examined to better estimate and reduce the error, new asymptotic stopping power parameters are obtained from improved Al and Ni ion optical oscillator strengths, and Ni stopping power results are presented with an estimated accuracy of 20%.
Output characteristics of an optically pumped Ta vapor laser
Authors: Yoshida H. , Ninomiya H. , Takashima N.
Published: July 2002

Output characteristics of an optically pumped tantalum vapor laser and the distribution of tantalum vapor generated by irradiation of a laser have been investigated experimentally. Ta vapor is generated by irradiation of a pulsed YAG laser and then the Ta atoms are optically pumped by a KrF excimer laser. It is observed that the maximum output energy is 160 nJ, the maximum optical conversion efficiency is 0.01%, and the ground-state Ta atoms are distributed not only in the luminous space of the vapor but also around it.
Computer simulation of dose effects on composition profiles under ion implantation
Authors: Miyagawa Y. , Ikeyama M. , Saito K. , Massouras G. , Miyagawa S.
Published: July 2002

Here is presented a computer code ‘‘dynamic sasamal,’’ which has been developed to simulate the dose dependence of concentration profiles and sputtering yields under ion implantations. The model calculations have been applied for high dose implantations of 50-keV nitrogen into zirconium and aluminum. The results are compared with composition profiles obtained by Rutherford backscattering spectrometry (RBS) and with semiempirical values. In the case of Zr, agreements between calculated composition profiles and experimental profiles obtained by RBS analysis were excellent for all fluences up to 1018 ions/cm2 and the calculated sputtering yield decreased toward the semiempirical value with the increase of the fluence. In the case of Al, for fluences up to 7.5×1017 ions/cm2, the composition profiles obtained by RBS measurements agreed well with the calculated results, but for a fluence of 1×1018 ions/cm2, the measured profile deviated from the calculated one; while the calculations assume a saturation concentration equal to the saturated nitride phase, nitrogen concentrations of 55% were measured within the mean ion range.
Electron paramagnetic resonance characteristics of the Mn activator in a ZnS:Mn electroluminescent device
Authors: Lee Yun-Hi , Oh Myung-Hwan , Choh Sung-Ho
Published: July 2002

We report electron paramagnetic resonance (EPR) results on the characteristics of the Mn activator in a ZnS:Mn thin film as a function of the film processing conditions. From the x-ray diffraction and EPR measurements of Mn in both ZnS:Mn powder and thin films deposited at the different substrate temperature and thermally treated in the vacuum, it was found that the effective Mn2+ concentration in a ZnS:Mn electroluminescent device could be changed by the annealing process, as well as the substrate temperature, during deposition.
Contrast reversal for domain image enhancement with garnet film rotator in a polarizing microscope
Authors: Numata Takuhisa , Wakabayashi Kouichirou , Inokuchi Seiji
Published: July 2002

A magnetic garnet thin film was used as a polarization rotator to reverse the weak contrast of magnetic domain images in a polarizing microscope. It was installed in a microscope and magnetized alternately at the video frame rate along the optical axis. This enabled the contrast of magnetic images to be improved by subtracting reversed images without disturbing the domain configuration to acquire a nonmagnetic background image. The contribution of magnetic circular dichroism of the garnet rotator was also studied. When the rotation θg and the ellipticity χg of the rotator match those of domains of Kerr rotation, θk, and ellipticity, χk, to be observed, (i.e., θkθgχkχg≳0,) the domain image contrast is enhanced compared to the absence of an ellipticity in the rotator. On the other hand, when θkθgχkχg<0 the contrast is deteriorated, but with the help of a quarter-wave plate the contrast is enhanced. The differential acquisition of domain patterns was also performed at an interval of 100 ms for moving domains which cannot be observed without differential technique.
Investigation of the electrical properties of Cd-doped indium selenide
Authors: Micocci G. , Molendini M. , Tepore A. , Rella R. , Siciliano P.
Published: July 2002

Resistivity, Hall-effect, and deep-level transient spectroscopy measurements have been performed on Cd-doped InSe single crystals grown by the Bridgman–Stockbarger method. The temperature dependence of the hole mobility can be explained by combining the optical phonon and the ionized impurity scatterings. Two hole-trapping levels have been detected at 0.42 and 0.48 eV above the valence band with a capture cross section of about 10−17 cm2. Finally, we have found the latter trap to be a deep acceptor level, which is very probably associated with defects or defect complexes formed by the dopant atoms.
Optical nonlinearities and ultrafast charge transport in all-binary InAs/GaAs strained hetero n-i-p-i’s
Authors: McCallum D. S. , Huang X. R. , Dawson Martin D. , Boggess Thomas F. , Smirl Arthur L. , Hasenberg T. C. , Kost Alan
Published: July 2002

We use picosecond differential spectroscopy to temporally and spectrally resolve the formation and decay of nonlinearities and space-charge fields in a hetero n-i-p-i that contains quantum wells in the intrinsic regions that are composed of all-binary InAs/GaAs short-period strained-layer superlattices. The evolution of the optical response is determined by competition between excitonic bleaching and the excitonic shift caused by screening of the built-in electric field of the n-i-p-i. The relative contributions of the two resulting optical nonlinearities are complicated functions of fluence, time, and wavelength, with the detailed dynamics determined by thermionic emission from the wells, picosecond charge transport over nanometer dimensions, screening, and recombination. At low fluences, excitonic bleaching is the source of an ultrafast nonlinear response that can be turned on and off in <10 ps. This initial excitonic bleaching gives way to a blue shift of the exciton as the carriers escape the wells in ∼3 ps and drift to screen the built-in field in <10 ps. The blue shift persists until the carriers recombine nonexponentially on microsecond time scales. At higher fluences, excitonic bleaching and the blue shift are observed simultaneously, since only a fraction of the carriers are required to screen the field and the wells remain partially occupied. On the time scale of ∼10 ns, the bleaching contribution disappears as the carriers within the wells recombine, leaving only the persistent blue shift.
Current step in I-V characteristic of an annular Josephson junction
Authors: Wang Wei , Wang Qianghua , Yao Xixian
Published: July 2002

The fluxon, or circularly symmetric soliton, propagating in an annular Josephson junction has been studied by using an energy analysis and a direct numerical simulation. The internal radius is set to be very large and the dissipation very small in the analysis, so that their effects are assumed only to modulate the velocity and position of the soliton slowly. The dynamical equations which govern the modulation (or the soliton motion) are derived. The first current steps in the I-V characteristic have been obtained both in the absence and presence of an applied external field. The analytical and numerical results are in good agreement with each other in the absence of the applied external field. When an applied external field exists, the height of the numerically simulated steps is smaller than that of the analytical ones.
Dopant diffusion in semiconductors moderated by dopant-dopant interactions. II. Extension of theory and application to boron and gallium in silicon
Authors: Aronowitz Sheldon
Published: July 2002

A macroscopic theory of dopant diffusion moderated by dopant-dopant interactions is extended to include three-dimensional effects. Application to dopant diffusion in thin crystalline silicon films when a second dopant, present in high concentration and distributed uniformly throughout the film, results in unanticipated predicted dependency on thickness for very thin films. Further application to boron-gallium diffusion patterns in silicon illustrate the success of the theory to describe relatively fast diffusing dopant species that also are strongly interacting.
Spatiotemporal evolution of a low-pressure glow discharge
Authors: Mark P. , Müller K. G.
Published: July 2002

The spatiotemporal evolution of a pulsed low-pressure glow discharge is investigated theoretically and experimentally. The discharge is modelled phenomenologically by a reaction-diffusion equation in which the cathode fall and the negative glow of the discharge are described as a bistable layer. A laterally one-dimensional discharge is realized experimentally by a hollow cathode discharge in a slotted cathode. With the help of probe measurements, a homogeneous evolution with a laterally uniform current rise and an inhomogeneous evolution starting from special sites and progressing along the cathode are found. The main experimental results are reproduced by model calculations.
Metamagnetism of RCo2 compounds
Authors: Nordström L. , Brooks M. S. S. , Johansson B.
Published: July 2002

Self-consistent spin-polarized energy-band calculations are reported for the RCo2 compounds (R=Tb–Yb). By changing the magnitude of the 4f spin in GdCo2 from zero to seven and back to zero, hysteresis was obtained with both low- and high-moment conduction-electron states being obtained for spin less than 4. For the real compounds, when the calculations were started with no moment on the Co, low-conduction-electron moments were obtained for DyCo2–YbCo2. However, when the calculations were started with large moments on the Co the total conduction-electron moments were calculated to be 1.75 μB/f.u. for all of the compounds. It is suggested that the conduction-electron-state densities in all of the compounds are similar to those in YCo2 and LuCo2 and that the conduction-band system is essentially metamagnetic.
Oriented grain growth in rapidly quenched Nd-Fe-B ribbons
Authors: Fujimoto T. , Mukai T.
Published: July 2002

A strong anisotropy is induced in melt-spun and hot-pressed Nd-Fe-B ribbons by a specific heat treatment such as a slow heating up to 1000 °C. The present study clarifies the origin of the induced anisotropy through microstructural observations. The following grain growth of Nd2Fe14B grains during heating has been observed: (I) As-quenched Nd2Fe14B grains grow coarser at the roll side of the ribbons at around 750 °C, and at the front of the coarse-grain region a Nd-rich region is formed. (II) A rapid grain growth of some of the coarse grains (excessive grain growth) occurs at an interface of the two regions at around 800 °C. The grains which have their c axes parallel to the ribbon thickness direction grow at a faster rate along a band of the Nd-rich region. Such preferential grain growth in stacked ribbons results in the enhancement of magnetization in the press direction.
Effect of NdF3 and NdCl3 substitution for Nd2O3 on the reduction–diffusion process of Nd–Fe–B powders
Authors: Liu T. Y. , Chen C. J. , Lin C. H. , Chang W. C.
Published: July 2002

The effect of partial substitution NdX3 (X=F or Cl) for Nd2O3 on the reduction–diffusion (R/D) process of Nd–Fe–B powders has been investigated. NdX3 reacts with Ca in the R/D process to produce CaX2. CaCl2 is distributed uniformly around the Nd2Fe14B grains after reaction. During water washing, CaCl2 reacts quickly with water. This improves the disintegration of compacts and facilitates the removal of Ca. The best results with residual Ca content of 400 ppm and oxygen content of 3000 ppm were obtained. In the case of fluoride, however, a negative result was found. There was no improvement in the disintegration of fluoride compact. This was due to the poor water affinity of CaF2.
Photoelectron spectroscopic study of 6.5-wt % Si-Fe alloy
Authors: Hiura A. , Tanaka Y. , Takada Y. , Iri T.
Published: July 2002

The electronic states of a range of Fe-Si alloys were investigated by x-ray and ultraviolet photoelectron spectroscopy. Previous work has shown that in Fe-Si alloys, the 6.5-wt % Si-Fe alloy has the optimum soft magnetic properties because of its zero magnetostriction. The binding energy (BE) of the Fe 2p, Fe 3s, Fe 3p, and Si 2p levels and the Fe 3d valence-band structures of Fe-Si alloys were measured over the range from 0 to 7 wt % Si. The BE of the Fe 3s and Fe 3p levels and the Fe 3d valence band of Fe-Si alloys showed small shifts of the peaks toward higher BEs than pure Fe. These peak shifts are related to the change in density of Fe 3d states with the addition of Si: the decrease in the density of states near the Fermi energy, the decrease in the energy difference between the majority and minority spin bands, and the increase in the number of electrons with minority spin. The results of the photoelectron spectroscopic analyses agree with the observed decrease in saturation magnetization from 2.15 T for pure Fe to 1.80 T for 6.5-wt % Si-Fe.
Effect of size and geometry on levitation force measurements between permanent magnets and high-temperature superconductors
Authors: Cha Y. S. , Hull John R. , Mulcahy Thomas M. , Rossing Thomas D.
Published: July 2002

A series of experiments measuring the levitation force between a permanent magnet (PM) and a high-temperature superconductor (HTS) and between pairs of PMs, coupled with finite-element calculations of the forces and fields, has identified factors that influence the levitation force. The self-demagnetizing factor within the HTS and, to some extent, within the PM has a profound effect on magnetic pressure. For large HTSs with strong flux-pinning, the demagnetizing effect of the diamagnetic image of the PM is substantial. For short distances between the HTS and PM, compression of magnetic flux produces a dependence on PM diameter.
Magnetostriction in surface crystallized Fe- and Fe-Ni-based metallic glasses
Authors: Thomas A. P. , Gibbs M. R. J. , Vincent J. H. , Ritchie S. J.
Published: July 2002

By measurement of λe, Hc, and χ0, we demonstrate that surface crystallization offers a viable method of controlling the magnetostrictive response of metallic glasses. Peak strains of 60 ppm with Hc = 10 A/m and χ0=104 can be achieved.
Magnetism in single-crystal Dy below 10 K
Authors: Willis Frank , Ali Naushad
Published: July 2002

The resistivity, ac susceptibility, and thermal expansion of single-crystal Dy have been measured at temperatures below 10 K. Single-crystal Dy is known to have a ferromagnetic structure with the magnetic moments confined to the basal plane at temperatures below Tc=90 K. At temperatures between Tc=90 K and TN=180 K, single-crystal Dy has a spiral antiferromagnetic arrangement of the magnetic moments with the screw axis along the c axis. The existence of an additional anomaly near T=6 K in ac susceptibility measurements of a very pure single crystal of Dy has been reported previously. Further evidence for a low-temperature transition (T<6 K) in single-crystal Dy is reported. The earlier ac susceptibility anomaly has been reproduced using a second, independently prepared crystal. Thermal-expansion data show a second-order phase transition near 5.9 K. A step has been observed intermittently in the resistivity along the a and c axes at 6.5 and 6 K, respectively.
Structural and magnetic properties of Fe/W superlattices
Authors: Xiao J. Q. , Chien C. L.
Published: July 2002

Fe(110)/W(110) superlattices with various Fe and W layer thicknesses have been fabricated by magnetron sputtering and studied by x-ray diffraction (XRD) and superconducting quantum interference device (SQUID) magnetometry. Detailed x-ray analysis reveals that, while the superlattice structure is faithfully reproduced throughout the samples, there is noticeable interdiffusion between the Fe and W layers. Consequently, within the intermixed region a diminution of the Fe moments is observed, while the remaining Fe moments have values close to the bulk value.
Magnetic properties of Fe-N/Al-N multilayered films prepared by Ar ion-assist sputtering
Authors: Kubota K. , Naoe M.
Published: July 2002

Fe-N/Al-N multilayered films were prepared by Ar-ion assist sputtering. The contents of nitrogen incorporated into the films were controlled by changing the nitrogen partial pressure in the mixture of Ar and N2 introduced into the sputtering ion source. The effects of Ar-ion bombardment onto growing film surfaces and post-annealing on their crystal structure and magnetic properties were investigated. The films with Fe and Al layer thicknesses of 50 and 10 Å deposited at ion bombarding voltage of 250 V and post-annealed at 150 °C possessed the saturation magnetization 4πMs of 16.2 kG and the relative permeability of about 4300. From those results, dual ion beam sputtering with Ar-ion bombardment is useful for controlling the crystallinity and magnetic anisotropy to prepare the soft magnetic Fe-N/Al-N multilayered films with large saturation magnetization.
Magnetic properties of permalloy wires in vycor capillaries
Authors: Lubitz P. , Ayers J. D. , Davis A.
Published: July 2002

Thin wires of NiFe alloys with compositions near 80% Ni were prepared by melting the alloy in vycor tubes and drawing fibers from the softened glass. The resulting fibers consist of relatively thick-walled vycor capillaries containing permalloy wires filling a few percent of the volume. The wires are continuous over considerable lengths, uniform in circular cross section, nearly free of contact with the walls and can be drawn to have diameters less than 1 μm. Their magnetic properties are generally similar to bulk permalloy, but show a variety of magnetic switching behaviors for fields along the wire axis, depending on composition, wire diameter, and thermal history. As pulled, the wires can show sharp switching, reversible rotation or mixed behavior. This method can produce NiFe alloy wires suitable for use in applications as sensor, memory or inductive elements; other alloys, such as supermalloy and sendust, also can be fabricated as fine wires by this method.
Preparation of CoxFe3−xO4 films in aqueous solution at 120–200 °C by ‘‘hydrothermal ferrite plating’’ (abstract)
Authors: Itoh T. , Zhang Q. , Abe M. , Tamaura Y.
Published: July 2002

Ferrite plating facilitates the formation of polycrystalline spinel films in an aqueous solution below 100 °C. The plating temperature can be extended up to 200 °C when the pressure of the reaction solution is kept high (15–20 kgf/cm2). We call this ‘‘hydrothermal ferrite plating,’’ by which solubility limit of Ni in Fe3−xNixO4 increases much, from x=0.3 (by conventional ferrite plating at 90 °C) to x=0.93.1 In this paper we describe preparation of Fe3−xCoxO4 films by the hydrothermal ferrite plating at T=120–200 °C and p=15–40 kgf/cm2, and report their structural and magnetic properties. Plating for 1 h, we obtained films about 1 μm in thickness, which are polycrystalline with no preferential crystal orientation as observed by x-ray diffraction. The solubility limit of Co, which is x=0.6 at 90 °C, increases to x=1.3 at 180 °C. The solubility limit of Co is higher than that of Ni, which may be because Ni tends to keep 2+ state in the spinel structure, while Co can take both 2+ and 3+ states. When prepared at 200 °C, the saturation magnetization of the films are smaller than that reported for bulk samples, though both agree when the films are prepared at 90 °C.2 This suggests that Co is oxidized to 3+ state even when x<1.0 as large as the Fe3−xCoxO4 films are prepared in the hydrothermal conditions. We found that adding CH3COONH4 into the reaction solution as a pH buffer improves the smoothness of the film surface.
Surface study of Nd-Fe-B sintered magnets by 57Fe conversion electron Mössbauer spectroscopy and thin-film x-ray diffraction technique
Authors: Hirosawa S. , Tanimoto H. , Nasu S. , Tokuhara K.
Published: July 2002

The structure and magnetic properties of surface of Nd2Fe14B anisotropic sintered compound were studied by 57Fe conversion electron Mössbauer spectroscopy (CEMS) and thin-film x-ray diffraction techniques using a very small glancing angle of incident x ray. CEMS as well as x-ray spectra of as-polished surfaces indicated that the structure and magnetic properties of surfaces of Nd2Fe14B are identical to those of the inner bulk. Heat treatment at 873 K for 3.6 ks under a 10−4 Pa vacuum resulted in a complete disproportionation of the surface into a mixture of randomly oriented bcc Fe and nonferrous oxides. Correlations of the features of the surfaces with coercivity and corrosion resistance are discussed.
An unidentified magnetic transition in R2Fe14X compounds (R=Sm, Tb, Dy, Ho, Er, and Tm; X=B or C)
Authors: Kou X. C. , Grössinger R. , Kirchmayr H. R.
Published: July 2002

In Ho2Fe14B and Ho2Fe14C the temperature dependence of the ac initial susceptibility between 4.2 and 300 K shows two peaks. The peak at the lower temperature can be explained by a well-known spin reorientation transition (at 62 K for Ho2Fe14B and at 40 K for Ho2Fe14C). The peak at the higher temperature (at 245 K for Ho2Fe14B and at 265 K for Ho2Fe14C) disappears when the external field is applied parallel or perpendicular to the preferential direction of a magnetically aligned sample. The similar peak was also traced for R2Fe14X compounds (R=Sm, Tb, Dy, Ho, Er, and Tm; X=B or C). Searching for the nature of this peak traced by measuring the temperature dependence of the ac susceptibility for 3d-4f compounds is still under progress.
Antiferromagnetic exchange contribution to Van Vleck paramagnetism in Fe-based magnetic semiconductors
Authors: Testelin C. , Rigaux C. , Mauger A. , Scalbert D. , Benoit à la Guillaume C. , Mycielski A. , Guillot M.
Published: July 2002

Magnetization measurements up to 20 T have been performed in Cd1−xFexTe (x<4%, 1.6≤T≤20 K) and Cd1−xFexSe (x=1.8%, T=1.7 K) for different crystallographic directions. A theoretical computation involving the diagonalization of the Hamiltonian of the isolated Fe2+ ion subjected to crystal-field, spin-orbit, and Zeeman terms within the lowest 5D manifold, provides the gross features of the magnetization curves, in particular their high field anisotropy. However, we argue that a quantitative agreement can be achieved only if the Fe-Fe spin interaction is taken into account. It includes not only the contribution of nearest-neighbor (nn) pairs or larger clusters, but also a sizeable Heisenberg interaction between more distant ions, treated in the mean-field approximation. Assuming a random distribution of Fe2+ ions, a quantitative agreement with experiments is achieved in the present domain of measurements. Exchange constants are also given.
Investigation of a Hamiltonian with two sources of anisotropy: The Dzyaloshinskii–Moriya and single-site interactions
Authors: Coffey Dermot
Published: July 2002

La2CuO4 is an S=1/2 system with almost tetragonal symmetry so that there is no single-site interaction term giving rise to anisotropy and the magnetic anisotropy of the system can be explained in terms of the Dzyaloshinskii–Moriya interaction which can lead to weak ferromagnetism even in a system with predominantly antiferromagnetic interactions. However, the closely related compounds, La2NiO4 and La2CoO4, are S=1 and S=3/2 systems, respectively, so that a single-site interaction term is present and it is of interest to see how this interaction changes the magnetic properties of these compounds. Here the classical magnetic ground states are calculated for model Hamiltonians, appropriate to the different low-temperature structural phases of the compounds, containing both interactions.
Local variations of the index of refraction of a Bi, Al-doped garnet film by laser annealing
Authors: Stashkevich A. A. , Gouzerh J. , Ben Youssef J.
Published: July 2002

The purpose of this paper is to understand the influence of laser annealing on the index of refraction of Al-doped ferrimagnetic garnet films in the near-infrared domain. It has been shown recently that a similar effect takes place in Ga-doped garnet films. According to theoretical predictions based on the photoelastic origin of the changes of the properties of a film after the local heat treatment, the effect of the variation of the index of refraction in Al-doped films should be several times greater than in the case of Ga-doped films. The experiment was carried out on Y1.73Bi1.23Fe3.69Al1.31O12 films. Phase diffraction gratings were fabricated in the films by means of laser annealing and thus a diffraction pattern of optical waveguide modes was analyzed with a photodetector. It has been shown that variations of the index of refraction as great as 10−3 were achieved. Thus it was demonstrated that the investigated effect is much stronger in Al-doped films compared to Ga-doped films. As in Ga-doped films, the dependence of the efficiency of diffraction on the number of an optical waveguide mode has been observed. That confirms the idea that the local value of the film thickness is changed as a consequence of the variation of the lattice parameter by heat treatment.
Comparison of magnetic and electrical properties of amorphous (Fe1−x
M
x)75Si15B10: M=Co, Cr
Authors: Bhatnagar A. K. , Rao G. Venugopal , Munirathnam N. R.
Published: July 2002

Amorphous (Fe1−xMx)75Si15B10 (M=Co, Cr and 0.00≤x≤0.12) metallic glasses have been investigated using Fe57 Mössbauer spectroscopy and electrical resistivity measurements. With Co substitution, hyperfine magnetic field (Heff) decreases initially and then levels off, whereas Curie temperature (Tc) initially increases before leveling off. Chromium substitution results, however, in a substantial decrease of Heff (∼6.5 kOe/at. % of Cr) and Tc (∼30 K/at. % of Cr). Hyperfine field distribution P(H) for Fe75Si15B10 does not change much with Co substitution but it shows substantial changes with Cr substitution. Temperature dependence of resistivity shows a minimum for both kinds of samples. The temperature at which a minimum in resistance is observed shows no shift with Co substitution, while the minimum increases in temperature with Cr substitution. Indirect evidence is presented for the magnetic contribution to the total resistivity for Fe-Co-Si-B samples.
Relationship between the structure and soft magnetic properties of FeRuGaSi films
Authors: Zeltser A. M. , Jagielinski T. M.
Published: July 2002

The effect of annealing on the structure and magnetic properties (coercivity, saturation magnetostriction, and initial permeability) of (FeRu)x(GaSi) films (x=2.5, 3.4, and 3.9) sputtered on MnNi-oxide and Li-silicate glass-ceramic substrates has been investigated. It is found that the best combination of soft magnetic properties (e.g., coercivity ≊0.3 Oe, permeability ≊1800 at 10 MHz, and magnetostriction < 1 × 10−6) is generally obtained after annealing between 450 and 500 °C independent of film composition, and subsequently deteriorate at higher annealing temperatures. This magnetic behavior is correlated with the crystal structure, grain size, and texture of the films as revealed by transmission electron microscopy and x-ray diffraction. It is found that after annealing, all films exhibit best soft magnetic properties when they consist of mostly the B2 phase and their magnetic softness decreases with the formation of the DO3 phase.
Magnetic properties of Dy2Fe17 and Dy2Fe17C
Authors: Tang N. , Liang J. Z. , Yu Mingjun , Lu Yi , Tegus O. , Li Q. A. , Chen G. M. , Liu Y. L. , Yang Fu-ming
Published: July 2002

The magnetic properties of Dy2Fe17 and Dy2Fe17C have been reported. The expansion of the lattice and increase of Curie temperature Tc and magnetization M have been found for Dy2Fe17C, and compared with Dy2Fe17. From the study of 57Fe Mossbauer spectra, we found that the average hyperfine field of Dy2Fe17C is about 5 T larger than that of Dy2Fe17. The isomer shift of the 4f site is smaller for Dy2Fe17C compared with Dy2Fe17.
Magnetic properties of Sm2(Fe1−xCox)17C and Y2(Fe1−xCox)17C
Authors: Kong Linshu , Yao Jiabin , Zhang Minghou , Yang Yingchang
Published: July 2002

The crystallographic structure and magnetic properties of Sm2(Fe1−xCox)17C with x equal to 0.0, 0.1, 0.2, 0.3, 0.4, 0.7, and 1.0, and Y2(Fe1−xCox)17C with x equal to 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 1.0 have been investigated. They crystallize in the rhombohedral Th2Zn17-type structure or the hexagonal Th2Ni17-type structure. The Curie temperatures increase with increasing cobalt content and the saturation magnetizations reach a maximum at x=0.3. All Sm2(Fe1−xCox)17C compounds have an easy axis, but the anisotropy fields have a dependence on cobalt content. Both Y2Fe17C and Y2Co17C have an easy plane. However, an easy axis is found in a concentration range with 0.4<x<0.9 for the substituted Y2(Fe1−xCox)17C compounds.
Spin glass transition in BaCo6Ti6O19
Authors: Batlle X. , Labarta A. , Martínez B. , Obradors X. , Cabañas V. , Vallet-Regí M.
Published: July 2002

Thermomagnetic ac and dc measurements were carried out on polycrystalline BaCo6Ti6O19. The system shows all the characteristic signatures of the spin glass syndrome. dc magnetic susceptibility displays a sharp peak at Tf = 13.6 K and below this temperature a clear onset of irreversibility between the zero field cooled and field cooled (ZFC–FC)processes is observed. The real part of the ac susceptibility shows also a sharp peak at Tf which strongly depends on the frequency of the ac magnetic field. The dynamic critical behavior of the system is studied by analyzing the imaginary part of the ac susceptibility in the scope of two models: the activated dynamic scaling and the equilibrium phase transition scaling. The best data collapsing is obtained assuming that a true phase transition occurs at the freezing temperature.
Overcompensated impurities in antiferromagnetic Heisenberg chains
Authors: Schlottmann P.
Published: July 2002

An impurity of spin S′=1/2 is introduced in the Babujian-Takhtajian Heisenberg model of spin S in one dimension. The impurity is located on the mth link of the chain and interacts with both neighboring sites. The interaction between impurity and Heisenberg chain is of a special type so that the integrability is preserved. The diagonalization of the transfer matrices leads to the Bethe ansatz equations of the model. The thermodynamics of the system is studied. For ferromagnetic coupling in the Heisenberg chain, the impurity is locked into the critical behavior of the lattice, i.e., at low temperatures the specific heat is proportional to T1/2 (ferromagnetic magnons) and the susceptibility diverges as T−2 (with logarithmic corrections). For antiferromagnetic coupling and S =1/2 the impurity is just one more site in the chain. If S ≳1/2 the collective properties of impurity and lattice give rise to critical behavior in complete analogy to the overcompensated n-channel Kondo problem. The zero-temperature entropy is finite in zero-field, but zero if the field is nonzero, giving rise to an essential singularity at T=H=0. As a consequence a two-peak structure arises in the specific heat in a small but finite field.
Self-consistent fluctuation theory for classical spin systems on 3D lattices
Authors: Garanin D. A. , Lutovinov V. S.
Published: July 2002

The thermodynamic properties of classical vector ferromagnetic models (D-component ‘‘spins’’ with n components interacting with each other) on 3D lattices are calculated in the 1/z approximation (z is the number of nearest neighbors) self consistently taking into account long-ranged Gaussian fluctuations of the molecular field. The numerical solution for the magnetization, susceptibility and the internal energy of a ferromagnet is valid in the whole plane (H,T) excluding the narrow region near the critical point (‖τ‖ ≲ 1/z2) and agrees well with available series results. In the spherical limit D→∞ the 1/z approximation becomes exact.