bluuebunny/crossref_metadata_2025 huggingface dataset:
Annealing effects on electrical properties of LiInSe2
Authors: Kamijoh T. , Kuriyama K.
Published: February 2003

The electrical properties of LiInSe2 single crystals are presented. As-grown LiInSe2 crystals have n-type conductivity and high electrical resistivity (1011 W cm at room temperature). Annealing in selenium atmosphere leads to p-type crystals having lower resistivity (105 W cm at room temperature). The origin of donors and acceptors in LiInSe2 are discussed through the annealing study. The energy band gap is estimated from the results of electrical resistivity measurements to be 1.91 eV. The value is supported by the optical transmission. A simple band diagram is proposed consequently.
Electrodynamic properties of ferromagnetic levitation systems revisited
Authors: Bohn G. , Langerholc J.
Published: February 2003

Previous formulae for the calculation of the electrodynamic parameters of a ferromagnetic suspension arrangement are generalized to take differences in track and core materials and dimensions into account. The results of these calculations are compared to some more recent measured values.
Deep-level transient spectroscopy system using a spectrum analyzer
Authors: Wang C. D. , Lin H. C.
Published: February 2003

In order to measure the thermal emission rate of a trap in semiconductor material without scanning the temperature, a new method, which utilizes a spectrum analyzer, has been developed. The theory on which our measuements depend is based on the relation between the time constant of a pure exponential wave and the relative amplitudes of its Fourier Components. The time constant is given by ts = (t/2r)[(10c−1)/(m2−10cn2)]1/2, where c = (Xn−xm/10, t is the period of the exponential wave, and xn and xm are the amplitudes of the nth and mth harmonics in dB, respectively.
Measurement of molecular stopping cross sections of vaporous sulfur compounds and calculation of the atomic stopping cross section of sulfur
Authors: Olson H. G. , Powers D.
Published: February 2003

The molecular stopping cross sections of hydrogen sulfide, methyl sulfide, methyl disulfide, carbon disulfide, ethylene sulfide, proplene sulfide, trimethylene sulfide, thiophene, and sulfur hexafluoride have beem measured for 0.3–2.0 MeV He+ ions. It is shown that the bond order correlation for the third period element sulfur is qualitatively in agreement with its second row counterpart, oxygen, but that the stopping cross-section dependence on bond order is considerably less (?5% in sulfur compared to ?17% in oxygen). In the energy region where the stopping contribution of the valence electrons is largest, the atomic stopping cross sections of sulfur for double-bonded, ring-structured, and single-bonded compounds decrease in the order eDB(S)≳eRING(S)≳eSB(S), a trend consistent with that observed for oxygen and carbon. The experimental results suggest a minimum d-orbital involvement in SF6 and reveal a lower peak energy Epeak and width d when S exists in the compound than when C, O, or F are present.
A generalized formulation of free-electron lasers in the low-gain regime including transverse velocity spread and wiggler incoherence
Authors: Gover A. , Sprangle P.
Published: February 2003

It is shown that in the small-signal, low-gain regime, an analytic expression for the gain can be derived which is valid for a general electron distribution function and general longitudinal variation of the transverse magnetic field pump. This expression is used to evaluate the effects on the gain curve due to transverse momentum spread in the beam as well as inaccuracies (incoherence) in the magnetic pump phase and amplitude. The restricting criteria for the neglect of these effects are derived.
Effects of the current distribution on the characteristics of the semiconductor laser with a channeled-substrate planar structure
Authors: Chen Chung Yih , Wang Shyh
Published: February 2003

Effects of the current distribution along the junction plane on the lateral- and longitudinal-mode behaviors of the semiconductor laser with a channeled-substrate planar (CSP) structure are investigated experimentally and theoretically. A new laser structure of the double-crurent-confinement CSP type, which has two electrodes for pumping and only one channel for stimulated emission (TEPOSE), was employed for this study. Current distribution profile of this laser can be varied by changing the relative strength of the current in each electrode. Experimental results showed that an asymmetric current profile can degrade the fundamental-lateral mode operation. A theoretical model based on phase-locked two-mode excitation was developed to account for the far-field pattern of a TEPOSE laser with only one electrode excited. It is also found that nonuniform excitation over the lasing mode can lead to a multilongitudinal mode operation, probably owing to nonuniformity in quasi-Fermi-level separation. The present study demonstrates the importance of symmetric and uniform current distribution in designing semiconductor lasers.
Influence of composition and structure on the ionic conductivity of the glass system Na2 O-B2 O3-SiO2
Authors: Catchings R. M.
Published: February 2003

The ionic conductivity, measured by the thermally stimulated current method, of ternary sodium borosilicate glasses is studied. The activation energy and preexponential factor, determined from the conductivity measurements, are studied as a function of the glass composition and fraction of BO4 and asymmetric BO3 units, as determined from the present structural model for this glass system.
Stoichiometry dependence of lithium outdiffusion in LiNbO3
Authors: Wood Van E. , Hartman N. F. , Austin A. E. , Verber C. M.
Published: February 2003

Measurements by Mach-Zehnder interferometry of the refractive-index changes near the surface of outdiffused LiNbO3 crystals indicate that, in agreement with recent results of Noda et al. [J. Appl. Phys. 51, 1379 (1980)], the rate of lithium outdiffusion is greater for more nearly stoichiometric crystals. The activation energy for diffusion of Li does not vary significantly with stoichiometry. The Li diffusion coefficient is also higher in the relatively Li-depleted regions near the surface.
Effect of band-gap narrowing on the built-in electric field in n-type silicon
Authors: Geist Jon , Lowney J. R.
Published: February 2003

A relation is derived to describe the change in the built-in electric field in an n-type semiconductor due to band tailing and carrier freeze-out, as well as band-gap narrowing. Recent numerical models of these various phenomena were used to illustrate the effect on heavily doped n-type silicon. While neither band-gap narrowing, band tailing, nor deionization alone is sufficient to explain the large decrease in the built-in electric field that has been inferred from experimental measurements, the combination of all three effects may be sufficient.
Formation of shallow Schottky contacts to Si using Pt-Si and Pd-Si alloy films
Authors: Eizenberg M. , Foell H. , Tu K. N.
Published: February 2003

A series of codeposited alloy films of Pt-Si with a composition changing from Pt75Si25 to Pt50Si50 and of Pd-Si changing from Pd75Si25 to Pd67Si33 have been prepared on Si for a systematic study of shallow silicide contacts. The effects of alloy composition and heat treatment on the formation and properties of these contacts have been investigated by I-V measurement of Schottky barrier height, glancing incidence x-ray diffraction, and cross-sectional transmission electron microscopy. Shallow contacts with a depth of about 10 nm and with the Schottky barrier height of PtSi and Pd2Si have been achieved.
Intermediate valence in rare-earth materials (invited)
Authors: de Châtel P. F.
Published: February 2003

The magnetic and other properties of compounds in which rare-earth elements occur with an intermediate valence are reviewed. A distinction between ’’metallic’’ and ’’covalent’’ systems is suggested. Strong similarities are found between mixed-valent materials, particularly of the metallic kind, and transition-metal or actinide systems which are reasonably well understood in terms of an itinerant-electron model. The parallel between intermediate valence and itinerant magnetism extends to dynamic properties as measured by quasielastic neutron scattering and X-ray photoemission spectroscopy. It is argued that photoemission spectra provide no information of the time-dependent properties of the initial state and therefore cannot provide an upper limit for the frequency of valence fluctuations.
de Haas–van Alphen measurements of mixed valent CeSn3 (invited)
Authors: Johanson W. R. , Crabtree G. W. , Koelling D. D. , Edelstein A. S. , McMasters O. D.
Published: February 2003

We present the first Fermi surface measurements of a mixed valent metal, CeSn3. We find a complex Fermi surface with at least nine separate frequency branches. The measured effective masses are very large, ranging from 4.2 to 9.2. The results directly confirm the existence of coherent Bloch states in CeSn3 and strongly support an itinerant model of mixed valence based on hybridized energy bands. We compare the Fermi surface properties of CeSn3 to those of LaSn3, a non-mixed valent reference metal, and discuss how the comparison allows various proposed models of mixed valence to be tested. Preliminary band calculations using only exchange in the density functional are able to reproduce many of the qualitative features of the CeSn3 data.
Mixed valence in alloys of SmSe with SmAs and SmP
Authors: Cater E. D. , Heslinga D. D. , Savage Wm. R. , Schweitzer J. W. , Beeken R. B.
Published: February 2003

Lattice parameter measurements are reported for a series of alloys of SmSe with SmAs and SmP. Also, magnetic susceptibility measurements are reported on the alloys of SmSe with SmAs and SmS with SmP.
Mössbauer study of mixed valence spinels
Authors: Grandjean F. , Gérard A.
Published: February 2003

X-ray and Mössbauer data on two spinel series Zn1−xGexFe2−2xMn2xO4 and (ZnMn2O4)1−y. (Zn0.5Ge0.5FeMnO4)y are presented. Cation distribution and valence are determined. It is shown that an electron delocalization takes place in the first series and that, even if the compounds do not show a quadratic distortion, Fe ions see a local distortion and consequently, large quadrupole splittings are observed in cubic spinels.
Theoretical considerations on the superconductor-ferromagnet transition region (invited)
Authors: Blount E. I.
Published: February 2003

We consider the effects of competing ferromagnetic and superconducting order parameters, specifically, in the regime where the exchange interaction between localized spins and conduction electrons is quite weak. This permits superconductivity to survive a high concentration of spins, and results in a weakened RKKY interaction between spins. There is then an important role for the long-range dipolar interaction, mediated by the magnetic field B. Working in mean-field theory, we find that there are at least five possible phases. There are, besides the pure superconductor and ferromagnet, state in which superconductivity survives with coexisting magnetization which may be periodic and linearly or circularly polarized, or concentrated in vortices. In the absence of anisotropy, these states may be quite close in free energy, so that anisotropy plays an important role. In the superconducting state, above the magnetic transition, there are interesting precursor effects, particularly a peak in the susceptibility at a finite wave number. This peak has apparently been observed. It persists and strengthens below the transition, in a manner suggestive of the spiral or linearly polarized state. At lower temperatures, this effect disappears and the material becomes simply ferromagnetic, as we should anticipate.
Low temperature magnetic and resistive behavior of the (Eu1−xSnx)yMo6S8 system
Authors: Willis J. O. , Thompson J. D. , Huang C. Y. , Luo H. L.
Published: February 2003

Magnetoresistance and ac susceptibility measurements have been made on sintered samples of the compounds (Eu1−xSnx)yMo6S8 for x = 0 and 0.1 at y−1.2 and x = 0 and 0.15 at y = 1.0. All samples show negative temperature coefficients of resistance in zero field in the range 4 to 0.02 K. For the pure x = 0 samples the resistance becomes constant below 0.5 K. The magnetoresistance is large and negative for all samples; at 2.4 T and below 0.5 K it is aobut 11% for y = 1.0 and 40% for y = 1.2. For the finite x samples the presence of superconducting second phases made detailed interpretation of the low field resistance data for x = 0.1, y = 1.2 and most of the data for x = 0.15, y = 1.0 somewhat ambiguous. The magnetoresistance saturates for all the samples below 1 K in fields of ∼2 T or greater. The susceptibility of all the samples has a peak near 0.3 K. The resistive behvaior of the samples is characteristic of a magnetic semiconductor. The susceptibility results point to magnetic ordering of the system near 0.3 K.
Pressure-induced superconductivity in (Sn, Eu)yMo6S8
Authors: Lim K. C. , Thompson J. D. , Harrison D. W. , Huang C. Y. , Luo H. L.
Published: February 2003

We have measured the resistance R and susceptiblity changes in (SnxEu1−x)yMo6S8, where 0⩽x⩽0.15 and y = 1.0 and 1.2, in the temperature range 1.5<T⩽250 K for varous hydrostatic pressures 0⩽P⩽21 kbar. For x⩽0.1 and P∼0, a resistance anomaly occurs at T∼100 K at which temperature dR/dT becomes negative and persists to the lowest temperatures attainable. The onset of the resistance anomaly, which we associate with a decreasing carrier concentration, shifts to lower temperatures as P is increased. For P∼7 kbar, these samples become superconducting even though the semiconductor-like resistance (dR/dT<0) remains. For 7⩽P⩽12 kbar, the superconducting transition temperature Tc increases sharply, even though the resistance anomaly persists. The Tc’s represent the highest pressure-induced superconducting transition temperature in any known low carrier density magnetic material We also discuss the effect of a magnetic field on the superconducting properties.
Anomalous positive magnetoresistance in the amorphous ferromagnet, GdNi3
Authors: von Molnar S. , Gambino R. J. , Coey J. M. D.
Published: February 2003

We report transport and specific heat measurements in amorphous Gd.23Ni.76Ar.01≊a-GdNi3. We find that the magnetoresistance is positive near the magnetic ordering temperature and estimate that the ratio of mean free paths, ℓ, to nearest neighbor Gd distance a, ℓ/a≃1.2. This result argues against nearly free electron theory. We suggest an apparent Ni moment as the most probable source of scattering.
Resistivity, magnetoresistance and Hall effect of FexGe1−x amorphous alloys
Authors: Cros Y.
Published: February 2003

The resistivity ρ, the transverse magnetoresistance and the Hall resistivity ρH have been measured in the amorphous FexGe1−x alloys for x from 0.1 to 0.6. The resistivity always decreases when T and x increases and is not sensitive to the appearance of magnetism. It is interpreted with a model requiring a mobility in the upper tail of the band where transport takes place. There is an Anderson transition around x = 0.5. We measure an isotropic negative magnetoresistance for 0.3<x<0.45 to which is superposed, for x≳0.45, an anisotropic negative magnetoresistance. The ordinary Hall effect is positive and independent of T. For x≳0.3, a term of anomalous Hall effect is added. Both effects have a particular behaviour due to the increase of the carriers localisation in these alloys.
Neutron scattering study of spin waves and exchange interactions in ferromagnetic and paramagnetic EuS
Authors: Bohn H. G. , Zinn W. , Dorner B. , Kollmar A.
Published: February 2003

The spin wave excitations of an 153EuS single crystalline sample have been measured by inelastic neutron scattering through the entire 1. Brillouin zone with the momentum Q parallel to the main symmetry directions 〈100〉, 〈110〉, and 〈111〉, and for temperatures ranging from well below (1.3 K) to well above (36 K) the Curie temperature (Tc = 16.6 K). Least square fits of the low-temperature spin wave dispersion curves to the Holstein-Primakoff theory yielded the exchange energy constants Jr of the Heisenberg operator up to the fifth (r = 5) Eu-Eu-neighbour interactions as follows: J1/kB = 0.22(1±3)K, J2/kB = −0.10(0±4)K, J3/kB = 0.00(6±2)K, J4/kB = −0.00(7±2)K, and J5/kB = −0.00(4±2)K. They correspond with Θp = 21.1±0.2 K and also with the theoretically expected ratio of Tc/Θp. The temperature dependence of the spin wave energies, which has been measured for large-q spin-waves up to T/Tc = 1.5, does not agree with the spin-wave renormalization theory. This EuS-result differs from EuO, where the spin-wave renormalization was reported to agree with theory. The variation of the Jr with magnetic dilution is discussed by considering related results on the EuxSr1−xS system.
Theory of excitation behavior for Ce3+ systems with Coqblin-Schrieffer interaction
Authors: Yang David , Cooper Bernard R.
Published: February 2003

Following Siemann and Cooper, we consider the Ce3+ system with Coqblin-Schrieffer-type (CS) interaction, and examine the excitation behavior of the system. We first show that longer-range antiferromagnetic CS interaction stabilizes the type IA ordering, and yields phase transitions in the applied field, in agreement with experiment. The excitation spectra for ferromagnetically ordered CS systems, including the field induced system, are then calculated in RPA. The spectra show anisotropic dispersion, and yield a low lying mode for q↘ along the direction of magnetic ordering. In the system which orders ferromagnetically in the zero field, this mode has zero energy at the zone center. In the field induced ferromagnet, the low lying mode shows finite gap, with a minimum at (0, 0,π/a), halfway to the zone boundary.
Neutron scattering study of the spin waves and magnetic structures in pure and metal-deficient V2O3
Authors: Yelon W. B. , Werner S. A. , Word R. E. , Honig J. M. , Shivashankar S.
Published: February 2003

We have carried out inelastic neutron scattering measurements of the spin waves propagating along the (00ℓ) trigonal axis and along the (hh0) axis in the antiferromagnetic phase of pure V2O3. We find an energy gap in the spin wave spectrum at the zone center at 4.75 meV. We obtain exchange parameters and the anisotropy energy from this data using a nearest neighbor and next nearest neighbor Heisenberg Hamiltonian Model. Elastic neutron scattering on V2O3.0198 has shown two distinct transitions. Magnetic ordering occurs at ∼100 K and the magnetic moment reaches ∼0.5μB at 50 K where the metal-insulator (M–I) transition occurs and the moment saturates at 0.9μB. This contrasts sharply with pure V2O3 in which the magnetic and M-I transitions coincide and with higher oxygen concentrations for which the M-I transition is completely suppressed. In addition, magnetic intensity observed at the 3/2,3/2,3 position in both pure and metal-deficient specimens suggests a magnetic contribution from the oxygen sites.
Temperature effects on EPR spectra of a linear chain copper complex-copper calcium acetate hexahydrate
Authors: De D. K.
Published: February 2003

The observed angular dependence of the electron paramagnetic resonance linewidth in the ab and ac planes of CuCa(AC)2, 6H2O in the temperature interval 77K–12K was explained by considering dipolar interactions along with hyperfine and isotropic exchange interactions in these two planes. It was found that this so called linear-chain copper compound can be better described by a three dimensional paramagnet. The exchange interaction is very nearly isotropic with values Jab = 0.0098 cm−1 and Jc = 0.0103 cm−1. The values of the A⊥ derived from the linewidth fit in the ab plane are 14G at 77K and 60.5G at 1.2K. Due to insufficiency of data in the ac plane, the fit was done with the measured value of A∥. Although the exchange interaction has been found to be temperature independent the hyperfine interaction increases very much at low temperatures. The high temperature (300–460K) EPR spectra are quite different from the low temperature spectra. High temperature differential thermal analyses and thermogravimetric analyses have been carried out and corroborated with the EPR findings.
Enhancement of uniaxial anisotropy constant by introducing oxygen vacancies in Ca-doped YIG
Authors: Hsia L. C. , Wigen P. E. , De Gasperis P. , Borghese C.
Published: February 2003

Ca-doped YIG films having composition Y3−x3+ Cax2+ Fe3+5−x Fex4+ O1 2 have been grown with a value of x = 0.25 and thickness 1.15 μm. Upon annealing in saturated FeCl2 solution, oxygen vacancies are introduced, which compensate for Ca2+ ions and reduce Fe4+ ions to Fe3+ ions. The uniaxial anisotropy constant changed from −5.89×103 erg/cm3 to −17.0×103 erg/cm3, which is consistent with a change in the crystal field effects reduction as proposed by Stacy and Rooymans. The exchange stiffness coefficient changed from 3.19×10−7 erg/cm to 3.66×10−7 erg/cm. The exchange stiffness parameter and the anisotropy energy have been studied as a function of temperature and oxygen vacancy concentration.
Surface acoustic wave propagation in paramagnets and ferromagnets
Authors: Kingner C. , Heil J. , Lüthi B.
Published: February 2003

Experimental results on SAW propagation in paramagnets and ferromagnets are presented. In the paramagnetic phase of CeAl2 we found crystal field effects on the SAW velocity. A magnetic field has a drastic effect on the SAW velocity depending on magnetic field and propagation direction. Interference effects between normal modes of SAW have been observed and quantitatively interpreted. In ferromagnetic nickel we observed strong domain wall-stress effects in SAW propagation at low temperatures.
’’Two-port’’ magnetostatic wave resonators utilizing periodic metal reflective arrays
Authors: Brinlee W. R. , Owens J. M. , Smith C. V. , Carter R. L.
Published: February 2003

Single-port and two-port magnetostatic surface wave (MSSW) resonators have been demonstrated. These devices, based on etched groove array reflectors have shown high loaded Q’s (≳800) and clean resonance characteristics. A primary drawback lies in the fact that the reflective arrays must be accurately etched in the epitaxial YIG film, a complex and expensive process. This work reports the first use of etched metal reflector arrays to form resonant structures. A theoretical model is derived and applied to a two-port model of the device. Simpler to fabricate, the structure shows Q’s of ∼600.
Brillouin study of phonons, magnons and magnetoelastic coupling in the antiferromagnet KNiF3
Authors: Ganot F. , Dugautier S. , Moch P. , Nouet J.
Published: February 2003

Brillouin scattering by magnons and acoustic phonons in KNiF3 has been studied as function of the temperature. At low temperature, we observe unusually large splittings of the phonon Brillouin lines, related to the multidomains structure of the samples. Using our determination of the anisotropy constant, K = 1.1×104 erg/cm3, we calculate from the splitting of the longitudinal [1, 1, 0] phonon a magnetoelastic coefficient ‖b2‖ = 3.3×107 erg/cm3. We also study the domains reorientation under an applied magnetic field.
Cross-sectional structures and depth profiles in bias sputtered GdCo films
Authors: Yasugi Shin-ichi , Honda Shigeo , Ohkoshi Masatoshi , Kusuda Tetsuzo
Published: February 2003

Structures and compositions of sputtered GdCo films were carefully investigated using a carbon-replica technique and Auger electron spectroscopy. In zero-bias sputtered films, the columns are clearly observed to develop perpendicular to the substrate, and they become fine with increasing Gd content up to near the compensation composition from pure Co film. For negative-bias sputtered GdCo films having near compensation composition, the film structures become fine with increasing negative bias up to 200 V. The observed increment of perpendicular anisotropy in this negative bias region was explained by the structural change of the columns (shape anisotropy and stress induced anisotropy). Above 200 V negative bias, the column structures are damaged partially by Ar-ion-bombardment, and then the anisotropy decreases due to the damage of columns. The change in the saturation magnetization due to negative bias was interpreted by the change in the film composition; Gd-content and oxygen.
Observation of a magnetoelectric aftereffect
Authors: Rado G. T. , Ferrari J. M. , Krishnan R.
Published: February 2003

The first observation of a magnetoelectric aftereffect is reported. Measurements were made of the electric polarization ΔP induced in the ’’skin’’ layer of lithium ferrite monocrystals by changes in an applied magnetic field H⃗. At temperatures, T, lower than 30°K, ΔP does not reach its equilibrium value until well after the changes in H⃗ are completed. In one experiment a sufficiently large H⃗ is rotated through an angle of π/2 from the principal axis of the crystal. In a second experiment H⃗ is applied along the principal axis. For both experiments the dependence of ΔP on t and T is successfully described by a newly proposed kinetic theory based on the superposition principle, a memory function, and a distribution of relaxation times τ = τ∞ exp (U/kT). Deduced from these experiments is the value U≃0.02eV, which suggests an electron hopping process, and a distribution of unexpectedly large values of τ∞ (10−4 to 10−2 sec), which may result from the ’’skin’’ layer inhomogeneity.
Growth-induced anisotropy arising from ordering of transition metal ions in garnets (invited)
Authors: Gyorgy E. M. , Luther L. C. , LeCraw R. C. , Blank S. L.
Published: February 2003

The earlier study of the growth-induced anistropy (Ku) in epitaxial YIG produced by the preferential occupation of Ir4+ on octahedral sites has been extended to include most of the transition elements that have degenerate ground states and that can be incorporated in the garnet lattice with the appropriate valence states. Among the 3d elements only Co2+ meets these requirements. For Co2+ charge compensated by Zr4+, Ku increases linearly with the Co/Fe ratio in the melt, reaching 2×105 ergs/cm3 in (111) films for a Co/Fe atomic ratio of 0.17. Among the possible 4d and 5d ions only Ru, Mo, and W are expected to be stable in the desired valence state. Ruthenium yields a large in-plane growth-induced anisotropy (Ku = −1.2×105). Lattice constant, SEM and optical studies indicate that Mo and W have negligible solubility in YIG. For as-grown bubble samples the coercive force (Hc) increase linearly with Ir content, as does Ku. For Ku = 2.3×105, Hc = 70 Oe. The increase of Hc with Ru concentration is substantially smaller. For Ku = −1.2×105, Hc = 2.5 Oe. For YIG (Ir, Ca) samples annealed to reduce Ku (initially 3.5×105) to zero, Hc is 3 Oe, indicating that Ir content alone does not cause the large coercive force. However to data we have not been able to produce an Ir containing material with an easy axis normal and a low value of Hc.
Garnet compositions for submicron bubbles with low damping constants
Authors: Robertson J. M. , Algra H. A. , Breed D. J.
Published: February 2003

Thin single crystalline films of composition (BiYLu)3(FeGa)5O12 have been grown by liquid phase epitaxy on 〈111〉 substrates with zero lattice mismatch. Optimisation of the Bi:Y:Lu ratio has lead to a 1 μm bubble film on Gd3Ga5O12 (Q = 3.6, 4 πM = 600 gauss and FMRΔH at 10 GHz = 2.8 Oe) and a 0.8 μm bubble film on Sm3Ga5O12 (Q = 2.7, 4 πM = 930 gauss and ΔH = 4.3 Oe). The dynamic coercive fields for these films was <1 Oe. Smaller bubble diameters seem to be feasible in this system. From ferrimagnetic resonance linewidth measurements at 10 GHz it appears that the damping constants in these films are only two times as high as in pure YIG. To increase the damping small concentrations of Sm have been added. For 3 μm bubble films a study of the correlation between the damping constants calculated from the FMR linwidths and the damping constants calculated from the bubble mobilities measured by a translation technique has been made. The agreement between these constants in these films was excellent.
Laser annealing of epitaxial garnet films under controlled atmospheres
Authors: Herman D. A. , DeLuca J. C. , Vollmer H. J.
Published: February 2003

Epitaxial films with a composition of Eu0.54Y2.41Pb0.03Fe3.84Ga1.18O12 have been laser annealed in forming gas, nitrogen, air and oxygen. Annealed films were studied using bubble statics, ferromagnetic resonance and x-ray techniques. Changes in the annealing ambient resulted in variations in the maximum saturation magnetization (4πMs) achieved, and in the laser power thresholds for film cracking and melting. In comparison with other atmospheres, oxygen allowed the use of greater laser power without film damage and yielded the highest saturation magnetization. The increase in 4πMs (above the as-grown value) produced by annealing in oxygen was more than 30% larger than achieved in air and more than 50% larger than reached in forming gas or nitrogen. The influence of an ambient is interpreted in terms of its abbility to suppress the formation of oxygen vacancies during laser annealing.
Magnetic field dependence of the domain wall mass
Authors: Morkowski J. , Wigen P. E.
Published: February 2003

The dependence of the 180 °-Block domain wall mass in a ferromagnetic thin film on a magnetic field parallel to the plane of the film was studied theoretically. The Slonczewski theory of the domain wall dynamics was generalized to take into account the distortion of the domain wall structure by the in-plane magnetic field. An essential aspect of the analysis is that both polar angles determining local directions of magnetic moments within the wall depend upon the distance from the symmetry plane of the wall. The case of an in-place field parallel to the domain wall was studied in detail. For small in-plane field H the domain wall mass is approximately m/mo = 1−(π/2)(Q+1)h+0 (h2 1n h), where Q = K/2πM2 and h = MH/2K (M is the saturation magnetization, K is the uniaxial anisotropy constant and mo is the Döring mass). Calculations of the domain wall mass for a field making a small angle with the domain wall were also done as well as an estimate of the influence of the cubic anisotropy on the domain wall mass.
Effects of dosage and annealing on the magnetic behavior of ion-implanted garnet films
Authors: Maartense I. , Searle C. W. , Washburn H. A.
Published: February 2003

The temperature dependence of the anisotropy is obtained from ac susceptibility measurements of bubble garnet implanted with 100 keV Ne+ ions. The dose- and annealing dependent behavior is examined, specifically the effects resulting from shifts in the layer’s ordering temperature, such as early indications of overdamage and increases in the anisotropy after annealing.
A conversion electron Mössbauer spectroscopy study on ion-implanted bubble garnets
Authors: Smit P. H. , Algra H. A. , Robertson J. M.
Published: February 2003

Conversion electron Mössbauer spectroscopy (CEMS) has been used to investigate the effects of ion implantation on the magnetic properties of bubble garnets. A decrease of the average hyperfine fields and therefore of the magnetization is observed with increasing implantation dose. Differences with the interpretation of CEM spectra from substituted YIG films, which recently apppeared in the literature, are resolved. Depth-selective Mössbauer spectra are obtained by combining etch experiments and CEMS measurements with the theory recently proposed for integral CEMS by Liljequist. In this way the hyperfine fields can be obtained at various depths, and quantitative estimates of the reduction of the magnetization through an implanted layer can be made.
High frequency propagation of magnetic bubbles in dual conductor devices
Authors: Verhulst A. G. H. , Bril T. W. , Voermans A. B. , Koel G. J.
Published: February 2003

Garnet epitaxial films with an orthorhombic anisotropy and a 1.7 μm bubble diameter have been grown under strong compression on 〈110〉 oriented G.G.G. substrates. The bubble mobility in these films is about 60 m/s ⋅ Oe and the maximum velocity is about 50 m/s. Dual conductor circuits with an 8 μm period have been processed onto these films with a planar processing technology. It has been shown that a Poly Tetra Fluoro Ethylene spacer reduces strongly the influence of the mechanical stresses in the overlay on the magnetic properties of the strongly magnetostrictive epi-layer. This spacer is necessary for good propagation characteristics. At 6 MHz propagation margins of 14% have been observed at a linear current density of 2 mA/μm.
Conductorless switching in ion-implanted magnetic bubble devices
Authors: MacNeal B. E. , Gergis I. S.
Published: February 2003

A new, conductorless switching concept for use in ion-implanted magnetic bubble devices is investigated. The switches consist of two passive merge gates with different orientations relative to the crystal axes placed back-to-back. Switching is achieved through a six-quadrant reversal of the rotation direction of the in-plane field. A small device was fabricated on 2μm YSmTmCaGeIG material using a single-masking-level process in order to test two-way switching between a 7.5μm×8.5μm storage array and a 17μm-period backward turn major loop. Results at 100 kHz operating frequency show a 22 Oe (9%) transfer margin at 60 Oe peak triangular drive, and a minimum drive field of 44 Oe. With this new concept, the problems of switch alignment and conductor crossing are eliminated while maintaining, the relatively large minimum lithographic features (2μm–3μm) associated with ion-implanted bubble technology.
A two-dimensional surface pole model for permalloy patterns
Authors: Lai F. S. , Watson J. K.
Published: February 2003

A method has been developed for modeling permalloy patterns for field access magnetic bubble devices, based on the distribution of poles rather than of magnetization. The present method has the advantage that the two dimensional distributions are of a single scalar quantity rather than two components of a vector quantity, which leads to numerical simplifications. The pole method also avoids the domain-continuum question and the question of uniqueness of magnetization distributions. The numerical simplification, reducing the size of the matrix that must be solved, leads to a shorter program implementation that makes it possible to address more complicated problems. The method takes into account permalloy-permalloy interactions between the nearby permalloy patterns of a periodic structure. The calculated potential profiles of a 3×15×0.4 μm3 rectangular bar are compared with the results of previous investigators. The versatility of this model is demonstrated by computing the potential profiles of a single chevron pattern used to propagate a cylindrical-shaped bubble domain and of a multiple chevron pattern used to transfer a stripe domain.
Magnetic properties of textured annealed commercial black plate
Authors: Krause R. F. , Popovic B. A.
Published: February 2003

A refined (001) [uvw] texture was developed in commercial black plate samples by annealing at 1150 C in a hydrogen atmosphere containing 20 ppm H2S. Long time annealing in the absence of intentionally added H2S resulted in a less refined texture, indicating that the texture is due to a surface energy phenomenon caused by the selective absorption of sulfur on the surface. Lower temperature anneals (925 C) in hydrogen resulted in very sharp texture development in all samples, independent of supplier, sheet condition, and gage; the resultant magnetic properties were excellent. Annealing at temperatures below the alpha-gamma transformation temperature resulted in a less refined texture and slightly poorer magnetic characteristics.
Incremental permeabilities for transient analysis of large turbine generators by the finite-element method
Authors: Minnich S. H.
Published: February 2003

The results of measurements of the incremental permeabilities on a sample rotor steel from a large turbine-generator are given. The use of the incremental permeability in finite-element solution of small signal, diffusion equation problems is described.
The magnetoresistivity, structure, and magnetic anisotropy of RF sputtered and E-beam evaporated NiFe films
Authors: Chi G. C. , Mogab C. J. , Burtherus A. D. , Lehner A. G.
Published: February 2003

Magnetoresistivity, magnetic hysteresis loop, and structure were studied on both RF sputtered (S-films) and E-beam evaporated (E-films) Ni81Fe19 films (4700 Å thick). The E-films were deposited on a rotating substrate (∼385 °C). The S-films were prepared on a stationary substrate with heat sinking. The room temperature magnetoresistivity (ΔR/R) were about 4.0% for E-films and about 3.7% for S-films. The ΔR/R differences for these two films resulted from higher resistivity of S-films. The structure of these films was investigated by TEM and X-ray techniques. The crystalline grain size was found to be 400 Å in diameter for S-films, and 800 Å in diameter for E-films. The x-ray diffraction patterns from a Read thin film camera revealed some preferred crystalline orientation for S-films. X-ray pole figures were taken for a closer measure of this texture. The results indicated that the S-films have (111) texture with their axes normal to the film plane. The magnetic properties for both films were observed with a MH loop tracer. Both films possessed low coercivity (about 1.5 Oe or less). The S-films were found to have in-plane magnetic anisotropy. Film stress and annealing effects were also studied. The differences of the observed resistivity and magnetic anisotropy for both films are attributed to an atomic ordering effect. The correlation of ΔR and texture is also discussed.
Some magnetic properties of Mn-Zn ferrite epitaxial layers
Authors: Herman D. A. , Plaskett T. S.
Published: February 2003

Mn-Zn spinel ferrite films grown by liquid phase epitaxy on MnGa2O4 substrates in controlled atmospheres have been studied. We have characterized films whose composition ranged from Mn.9Zn.5Fe1.6O4 for saturation magnetization, induced anisotropy, Curie temperature and in-plane coercivity. The ferromagnetic (FMR) and spin wave resonance spectra show the correlation of film magnetization, induced anisotropy and homogeneity with composition. Two magnetic phases are evident from the FMR spectra and hysteresis for films with a composition near Mn.9Zn.5Fe1.6O4. The second phase is not present in films with more than 1.7 Fe atoms/formula unit. The variation of the FMR linewidth with temperature is attributed to the presence of either Mn3+ or Fe2+. A large stress correlated (but not simply magnetostrictive) uniaxial anisotropy is apparent. Using a vibrating sample magnetometer film moments have been measured from room temperature through their Curie points. An in-plane coercivity of less than 3 Oe has been observed in a good quality film of composition near Mn.3Zn.2Fe2.5O4 and having a film/substrate lattice mismatch of approximately −0.002 Å (film in compression).
The effect of chromating on borohydride reduced iron powders
Authors: Baltz A. , Freitag W. O. , Greifer A. P. , Suchodolski V.
Published: February 2003

Iron powders with Hc between 350 Oe and 1000 Oe were prepared by borohydride reduction of ferrous sulfate. The powders were stabilized by a chromating procedure. This paper discusses the effect of the chromating as observed by: TEM, changes in surface area, O2 content, ESCA/Auger and adsorption. Chromating coats the surface of the particles with a layer of FeCr2O4. Oxygen content in chromated powders is generally ∼8% while in the unchromated powders, it varies between 11 and ≳16%. This increase in O2 can be correlated with a decrease in σs. Sheet-like impurities are observed in unchromated powders which have been identified as FeOOH. Chromating results in a reduction in surface area of the particles as measured by N2 adsorption. The stability of the powders is greatly improved with chromating. Powders subjected to 80% R.H. for 112 days showed that the unchromated powder lost 25% of its original magnetization, while the chromated powder lost only 3%. Simultaneously, a band of FeO and Fe2O3 formed around the particles. Adsorption studies of reference polymers have shown that chromating reduces the acidic surface sites of the powders.
The saturation magnetostriction of permalloy films
Authors: Klokholm E. , Aboaf J. A.
Published: February 2003

The saturation magnetostriction of permalloy films has been measured as a function of film composition. In general, the data obtained agrees with the published values for bulk polycrystalline permalloy. It has further been established that the composition for zero magnetostriction is at about 81.5 (wt.)% Ni. The exact composition for 0 magnetostriction is difficult to attain and for most films deposited under practical conditions the magnetostriction is small but slightly negative or positive. Various elements such as Cr, Rh, Ir and Ti have been added to permalloy films to enhance their corrosion resistance. The saturation magnetostriction of these films has been measured as a function of the amount of dilutent. All of the dilutents cause positive contributions to the saturation magnetostriction of permalloy films; Ir has the largest effect on λ, with the other elements Ti, Cr and Rh the effect on λ is less than Ir and decreases in that order.
Zero magnetostrictive amorphous alloys with high permeability and high magnetic induction
Authors: Sakakima H. , Senno H. , Yanagiuchi Y. , Hirota E.
Published: February 2003

The rapidly quenched zero magnetostrictive Co-Fe-Si-B amorphous alloys having high magnetic induction and high permeability have been studied. The magnetic annealing under the vertical magnetic field H⊥ and under the rotating magnetic field Hφ has been investigated to obtain high permeability even though the alloys have the Curie temperature Tc higher than the crystallization temperature Tx. A zero magnetostrictive amorphous alloy with saturation magnetization σs = 115 e.m.u./gr and with initial permeability μi = 8,000 at 1 kHz has been obtained using the new method of magnetic annealing.
The optical absorption of oxygen films on porous glass—Initial studies of a unique system
Authors: Awschalom D. D. , Lewis G. N. , Gregory S.
Published: February 2003

We report preliminary measurements of the optical absorption of oxygen adsorbed on porous glass. Results are discussed in terms of existing theory which relates the optical properties of oxygen to the observed magnetic interaction between molecules.
Analysis of the temperature dependent magnetic scattering by ferromagnetic Ni (110) surface
Authors: Wang Sheng-Wei
Published: February 2003

The temperature dependence of the bulk and layer-by-layer surface magnetization of Ni (110) is derived using the molecular field theory. We then use these results in a dynamical polarized low-energy electron diffraction (PLEED) calculation to determine the temperature dependent polarization S of the diffracted intensities. The S vs T curves are strongly dependent on the incident electron energies and the critical exponents for surface magnetization are different from the bulk case. Multiple scattering effects profoundly modify the results predicted by using the kinematical scattering approximations. We also examine the sensitivity of S upon the use of different spin-dependent scattering potentials of the surface atoms. These results are then compared with recent experimental data for 0.6 TCurie⩽T⩽TCurie. The usefulness of PLEED for surface magnetic structural determination is clearly demonstrated.
Temperature dependent properties of an anisotropic Mn-Al-C permanent magnet
Authors: Rothwarf R. , Leupold H. , Breslin J. T. , Tauber A. , Paul D. I.
Published: February 2003

The anisotropy field, coercivity and saturation magnetization in a Mn-Al-C permanent magnet were measured as a function of temperature from 4.2K to 300K. The coercivities in both the easy and hard directions were found to decrease linearly with temperature with slightly different slopes. The coercivities measured with the applied field along the hard direction were found to exceed those obtained when the field was aligned with the easy axis. A model for the mechanism producing this effect is discussed. The anisotropy field is found to decrease linearly with temperature while the reduced saturation magnetization follows a −T3/2 law.
Microstructure and properties of step aged rare earth alloy magnets
Authors: Mishra Raja K. , Thomas G. , Yoneyama T. , Fukuno A. , Ojima T.
Published: February 2003

Alloys with compositions Co-25.5 wt % Sm-8 wt % Cu-15 wt % Fe-3 wt % Zr and Co-Sm-Cu-Fe-1.5 wt % Zr have been step aged to produce magnets with coercive force (iHc) in the range of 10–25kOe, much higher than those reported so far in the literature for the Zr alloys. The high coercive force magnets are typically aged at 800–850 °C for 10–30 hours following the solution treatment at 1150 °C. Subsequently, these are step aged to produce materials with high coercivity. The microstructure in all these alloys has a two phase cellular morphology with 2:17 phase surrounded by a 1:5 boundary phase. The long aging treatments at 800–850 °C lead to coarsening of the two phase structure. The subsequent step aging does not change the morphology, but only changes the chemical composition of the two phases. Best properties are obtained in materials with a coherent microstructure of optimum boundary phase thickness and optimum chemical composition. The highest values of iHc obtained so far are ∼26kOe and ∼16kOe for the 3% Zr and 1.5% Zr alloys respectively. The best hard magnetic properties of (BH) max = 33 MGOe and iHc = 13kOe are for a 25% Sm-20%Fe-4 Cu-2% Zr alloy.
Temperature-sensitive Nd-Co compounds produced by powder metallurgy
Authors: Sagawa M. , Yamagishi W. , Henmi Z.
Published: February 2003

A powder metallurgical process has been developed to prepare Nd-Co compounds which show the spin reorientation (SR) phenomenon. In this process, single crystals of the compounds in fine powder form are aligned in a magnetic field at a temperature more than 50 °C above the SR temperature. Complete uniformity is especially important in the chemical composition of the powders. As a result of studying many elements as substituents in NdCo5, an Nd (Co1−x−yAlxFey)5 system has been developed. The SR temperature of this compound system can be extended beyond 150 °C by controlling composition of the compound as may be required for different applications.
Solid state and magnetochemistry of the SrO-Fe2O3 system IV. Synthesis of SrFe12O19 from coprecipitated precursors
Authors: Qian Xueyu , Evans B. J.
Published: February 2003

By means of 57Fe Mössbauer spectroscopy and powder x-ray diffraction techniques, it has been determined that the formation of SrFe12O19 from coprecipitated ferric hydroxide and strontium laurate follows a reaction mechanism different from that when SrCO3 and Fe2O3 are used as starting materials. Upon heating at 300 C in vacuum, strontium laurate decomposes and further heating to 550 C leads to the formation of γ-Fe2O3 from the ferric hydroxide and solid solution of SrO in γ-Fe2O3. This solid solution phase behaves as an intermediate and undergoes further reaction with γ-Fe2O3 to give SrFe12O19. No paramagnetic Sr-Fe oxide intermediate is formed. The low temperature of the reactions and the absence of paramagnetic intermediates offer new possibilities for controlling the textures and magnetic properties SrFe12O19 ceramic bodies.
Liquid phase sintered Sm-Co-Cu-Fe-Zr 2–17 type magnets
Authors: Wen-tao Xiao , Jing-han Zhu , Tian-duo Sun
Published: February 2003

The experiments have shown that the optimal total samarium content range of Sm(Co, Cu, Fe, Zr)Z 2–17 magnets is 27–27.5 wt%. Moreover it is difficult to obtain excellent magnetic properties by normal solid phase sintering. The use of the liquid phase sintering (LPS) technique is favourable to adjusting and controlling exactly the composition of the magnets and can fully exploit the advantage of the step aging treatment. As a result, the coercivity and energy product of magnets have obviously been increased. The magnets with the higher performance can be stably produced on a large scale. The highest (BH)m obtained is 30.5 MGOe.