bluuebunny/crossref_metadata_2025 huggingface dataset:
Eddy current analysis of thin film recording heads
Authors: Shenton D. , Cendes Z. J.
Published: February 2003

Due to inherently thin pole tips which enhance the sharpness of read/write pulses, thin-film magnetic recording heads provide a unique potential for increasing disk file capacity. However, the very feature of these heads which makes them attractive in the recording process, namely, their small size, also makes thin-film heads difficult to study experimentally. For this reason, a finite element simulation of the thin-film head has been developed to provide the magnetic field distribution and the resistance/inductance characteristics of these heads under a variety of conditions. A study based on a one-step multipath eddy current procedure is reported. This procedure may be used in thin film heads to compute the variation of magnetic field with respect to frequency. Computations with the IBM 3370 head show that a large phase shift occurs due to eddy currents in the frequency range 1–10 MHz.
Vacuum-deposited thin-metal-film disk
Authors: Rossi E. M. , McDonough G. , Tietze A. , Arnoldussen T. , Brunsch A. , Doss S. , Henneberg M. , Lin F. , Lyn R. , Ting A. , Trippel G.
Published: February 2003

The fabrication process used in an all-vacuum-deposition thin-metal-film disk will be described. The process consists of planar dc-magnetron sputter deposition of a stainless alloy undercoat onto a 14-in.-diameter AlMg-4 disk substrate, e-beam evaporation of an Fe–Co–Cr alloy magnetic layer at an oblique angle of incidence, planar dc-magnetron sputter deposition of a rhodium overcoat and spray deposition of a liquid lubricant layer. Some mechanical and magnetic performance characteristics of disks, deposited in that fashion, are described.
The magnetic and corrosion properties of iron cobalt chromium films
Authors: Phipps P. B. , Lewis S. J. , Rice D. W.
Published: February 2003

The influence of alloy composition on the magnetization and atmospheric corrosion of thin films has been measured. Films were prepared by sputtering from a target composed of separate segments of Fe, Co, and Cr. Film composition at different locations varied according to the different distances from the three segments in the source. Microprobe analysis was used to measure the compositions as a function of location. Compositions ranged from 75% to 10% Fe, from 75% to 10% Co, and from 45% to 5% Cr. From the relationship between composition and location in the film, properties measured at various locations could be interpreted as measurement on various compositions. A smooth surface was fitted to the measurements in the composition graphs to provide the benefits of averaging and interpolation. X-ray diffraction showed the compositional dependence of the phase boundaries in these films and provided lattice constants. Magnetic measurements were made by cutting the film into small enough pieces to have only minor composition ranges and by a magneto-optic method which sampled very small areas. Atmospheric corrosion was assessed by measuring the roughness induced by exposure to a corrosive gas test designed to simulate indoor atmospheres. These data are presented as contoured surfaces on composition maps.
Evidence for microstructural inhomogeneity in sputtered Co-Cr thin films
Authors: Smits J. W. , Luitjens S. B. , den Broeder F. J. A.
Published: February 2003

Thin films of the perpendicular recording material Co100−xCrx(x=17–23) were ion beam sputtered from alloy targets. The saturation magnetization and uniaxial anisotropy constant, as a function of temperature, both show a strong dependence on the substrate temperature during deposition Ts, indicating composition shifts which increase with Ts. The films have a columnar structure on a scale which does not depend on Ts in contrast to the grain size. From studies of the phase relations in bulk Co-Cr alloys and diffusion couples it is concluded that phase separation of ordered Co-Cr phases does not occur at high Ts. Instead the composition shifts and the grain refinement at higher Ts are proposed to be caused by oxygen gettering and oxide trapping during film growth.
Effect of atomic distribution on the saturation magnetization of cobalt-chromium films
Authors: Haines William G.
Published: February 2003

The saturation magnetization Ms of CoCr films as a function of Cr content and atomic distribution has been modeled. For homogeneous films, two distinct cases have been calculated. The first case is a random array of atoms in an hcp lattice, while the second is an array with the condition that there be no Cr-Cr bonds. Ms is calculated by summing up the Co atom’s contribution, counting only nearest neighbor interactions, and assuming that the Cr atom is nonmagnetic. The model assumes that the contribution of the Co atom to Ms is determined by its Cr nearest neighbors; for zero Cr nearest neighbors, the moment is maximum with the moment linearly decreasing to zero for four or more Cr neighbors. These two cases describe the range of behavior of Ms for CoCr films produced by rf diode sputtering with applied rf bias. For cold substrates with no bias, Ms is close to that predicted for the random distribution, while as the bias level is increased, Ms approaches that predicted by the no Cr-Cr bond distribution. For 20 at. % Cr, the two models predict moments of 480 and 220 emu/cc, respectively. Experimental data supporting the model are presented for Cr concentrations of 11–20 at. %. This model explains why sputtered films tend to have higher Ms values than do bulk samples. In addition, the effect of heat treatment on the magnetic properties of CoCr films is determined by the combination of atomic distribution in the grain and Cr segregation at grain boundaries.
Magnetic annealing and relaxation in cobalt-substituted acicular iron oxide particles
Authors: Kishimoto M. , Amemiya M. , Hayama F.
Published: February 2003

The magnetic anisotropy induced by annealing in a magnetic field and the activation energy were measured for cobalt-substituted acicular iron oxide particles using a torque meter. The induced magnetic anisotropy linearly increased with the cobalt content in the particles. The induced magnetic anisotropy at 293 K in the particles containing a cobalt of 1.6 wt. % was 1.1×105 erg/cc, and this value nearly agreed with the value reported in iron–cobalt ferrite. The change of coercivity in the particles was attributed to the induced magnetic anisotropy. The activation energy in the particles was 0.8–0.9 eV, and this value was close to the value reported in iron-cobalt ferrite.
Mössbauer spectrum of fcc Au alloys with 15%–19% Fe
Authors: Beck Paul A.
Published: February 2003

The two components of the 4 K Mössbauer spectrum of the alloys considered can be qualitatively accounted for if it is assumed that, in addition to the segregated two atomic layer Fe platelets previously found by x-ray diffuse scattering, platelets with three atomic layers of Fe are present as well. The variation of the relative intensities of the two components with the Fe content can also be explained with this model. The temperatures at which the hyperfine splitting starts in these alloys are considerably lower than the Curie temperatures where the ferromagnetic spin correlations develop within the individual magnetic clusters. A possible explanation is presented for the observed temperature dependence of the polarization of the Mössbauer spectrum by an applied field.
Hyperfine fields and magnetic moments of crystalline Co3−xFexB and glassy Co4−xFexB alloys
Authors: Wójcik M. , Lerchner H. , Deppe P. , Li F. S. , Rosenberg M. , Livingston J. D.
Published: February 2003

A Mössbauer and NMR study of crystalline orthorhombic Co3−xFexB has been undertaken. Two different 57Fe hyperfine fields, varying only slightly with x, corresponding to two types of Fe surroundings in the Co3B structure have been found. Fe moments in the range 2.15–2.23 and 1.73–1.87μB have been estimated. Transferred hyperfine field (THF) at 11B has a strong local character depending on the chemical and topological short-range order around B. Contributions to THF (B) from Fe belonging to the first six neighbors and to the next three neighbors have been separated and evaluated. An analysis of THF (B) for Co4−xFexB amorphous alloys has shown that in the glassy form the short-range order is similar to that in crystalline Co3−xFexB only in the case of Co4B.
Crystal fields and second-order magnetic hyperfine interactions in TmFe2Si2
Authors: Umarji A. M. , Shenoy G. K. , Noakes D. R. , Dattagupta S.
Published: February 2003

We report the measurement of Mössbauer hyperfine spectra of TmFe2Si2 using the 8.4 keV transition in 169Tm. The detailed temperature dependence of the quadrupole interaction has permitted us to evaluate the crystalline electric fields (CEF) acting on Tm atom. The analysis indicates the ground state of Tm to be a singlet state. However, the hyperfine coupling of the 169Tm with the excited CEF states generates a second order magnetic hyperfine interaction which has been observed in our experiment. An account of the spin relaxation of the second-order magnetic hyperfine interaction is presented.
Electron paramagnetic resonance linewidths in diluted magnetic semiconductors: Cd1−xMnxTe
Authors: Webb D. J. , Bhagat S. M. , Furdyna J. K.
Published: February 2003

We report measurements of EPR in the magnetic semiconductors Cd1−xMnxTe and reanalyze earlier data. Experimentally we find (i) the room temperature linewidth increases as x is increased, (ii) the g value, obtained by reference to the zero of the derivative curve, is almost independent of x, (iii) each resonance line has a symmetric lineshape, and (iv) for each x the linewidth increases as T is reduced. These facts suggest that the resonances are not relaxation broadened but are, instead, inhomogeneously broadened. We model this inhomogeneity in terms of a Gaussian distribution of internal fields and show that there is a sharp change in the x dependence of the corresponding Gaussian widths at the percolation threshold. We also note that the temperature dependence of the linewidths follows an empirical form proposed earlier for metallic spin glasses.
Magnetic properties of Pb1−xMnxTe
Authors: Tholence J. , Mauger A. , Escorne M. , Triboulet R.
Published: February 2003

Magnetic and transport properties of Pb1−xMnxTe have been investigated for Mn concentrations x<0.2. A spin glass behavior is observed below a freezing temperature characterized by a cusp in the reversible part of the magnetic susceptibility. Irreversible effects below Tg have been studied in detail. Although the materials are  p type with hole concentrations ranging from 6×1016 to 6×1019 cm−3, the Ruderman–Kittel–Kasuya–Yosida interaction does not affect significantly the magnetic properties. We attribute the spin glass properties to the interband exchange interactions, which are long range in a small gap semiconductor like Pb1−xMnxTe. The transport experiments give evidence to a strong deformation of the valence band upon introduction of Mn in the matrix. In particular, the experimental data are compatible with a crossing between valleys of the valence band at L points and valleys along the Σ axis of the Brillouin zone.
The metal insulator transition in the magnetic semiconductor: Gd3−xvxS4 (invited; abstract)
Authors: von Molnar S. , Holtzberg F. , Briggs A. , Flouquet J. , Remenyi G.
Published: February 2003

It is possible to tune through the metal insulator phase transition in the magnetic semiconductor Gd3−xvxS4 (where v=vacancy) by applying a magnetic field H. Contrary to similar effects observed in some ordinary semiconductors, the magnetoresistance is negative,1,2 indicating that the electronic states become more extended with increasing field. Here we present new transport measurements on samples with x=0.321 and 0.325, including the temperature dependence of the magnetoresistance near the phase transition. The principal result of the present study is that the transition is continuous in field. The low temperature conductivity, σ(T→0), obeys a linear relationship of the form σ(T→0)∝(H−Hc), which implies σ(T→0)∝(E−Ec), where Hc is a critical field and Ec is the mobility edge. Such behavior, in this analogue of a compensated semiconductor, is consistent with new scaling theories of both localization and interaction effects.
Novel spin-flop effects in FexMn1−xF2
Authors: King A. R. , Toussaint R. M. , Jaccarino V. , Motokawa M. , Sakakibara T. , Date M.
Published: February 2003

High-pulsed-field magnetization measurements in the randomly mixed antiferromagnet FexMn1−xF2, with 0.15≤x≤0.40, have revealed an extremely broad spin-flop transition, with a width of ΔH≂60 kOe. An unusual square shape, with rounded edges, is found in dM/dH, with an asymmetry which depends on x. For the largest values of x, an additional sharp peak is also seen. A four-sublattice molecular-field model has been used to interpret the results, and predicts a number of interesting effects. For 0.01≲x≲0.10, the usual first-order spin-flop is suppressed, and a new canted-intermedi ate (CI) phase appears, in which the spins rotate continuously from the antiferromagnetic (AF) to spin-flop (SF) phase. For 0.10≲x≲0.6, the CI–SF transition becomes first order, and for x≳0.6 the CI phase disappears, leaving a relatively normal first-order spin-flop. The model shows that small misalignments cause considerable broadening and rounding of the transition, and convincingly reproduces the experimental shapes and widths.
Magnetic properties of substituted W and X hexaferrites
Authors: Dey S. , Valenzuela R.
Published: February 2003

Magnetic measurements were performed on Sr-hexaferrites of type Me2+2–Sr(W) with Me2+2=Fe2+, Ni2+, Co2+, Zn2+, and Me2+-Sr(X) with Me2+=Fe2+, Zn2+ in the temperature range 5K 750 K. The Curie temperatures are found to be 781 and 721 K for Fe2-Sr(W) and Fe-Sr(X) systems, respectively. The saturation magnetization of a Zn2-Sr(W) hexaferrite has been observed to be maximum at 5 and 300 K among all the samples investigated, namely, 115 and 82 emu/g. The saturation magnetization of Fe2-Sr(W) and Fe-Sr(X) hexaferrites are almost the same, whereas at 300 K this value is higher for Fe2-Sr(W). The coercivity of the Fe-Sr(X) sample has been found to be higher than the Fe2-Sr(W) hexaferrite after 8 h of milling.
Antiferromagnetic ruthenium (III) (abstract)
Authors: Carlin Richard L. , Burriel Ramon , Seddon K. R. , Mennenga G. , de Jongh L. J.
Published: February 2003

Studies on the first antiferromagnetic coordination compounds of ruthenium (III) will be reported. The compounds are [Ru(NH3)5Cl]Cl2 and the series A2RuCl5⋅H2O (A=Cs, Rb, K). Susceptibilities and specific heat data will be reported, and comparisons will be made with the analogous iron (III) compounds.
Magnetic properties of Mn1−xMxAlGe (M=3d metals)
Authors: Ido H. , Kamimura T. , Shirakawa K.
Published: February 2003

Magnetic measurements are carried out for Mn1−xMxAlGe (M=3d metals) alloys with x up to 0.2. A remarkable increase and decrease of the Curie temperatures with x are observed for M=Cr and Fe, respectively. The substitution of M with x less than 0.1 brings about the reduction in the averaged magnetic moment, which is especially large in the cases of Ti, Fe, and Co and of about 20% for x=0.1. From the measurement of Mössbauer spectrum at 77 K, the internal field at Fe atomic site is not found in Mn0.8Fe0.2AlGe. The reciprocal susceptibility versus temperature curves do not obey the Curie-Weiss law and are concave upward for all the specimens. By adjusting the Curie-Weiss law to the tangents of the highest parts of the χ−1g vs T curves, we obtain values of magnetic moments about 20 (for M=Mn) to 45% (for M=Fe) larger than those obtained from the saturation magnetizations.
Low temperature magnetostriction in CsNiCl3 and RbNiCl3
Authors: Rayne J. A. , Collins J. G. , White G. K.
Published: February 2003

The forced magnetostriction of the linear-chain antiferromagnets CsNiCl3 and RbNiCl3 has been measured from 1.6–20 K. For the applied field parallel to the c axis the data below the Néel temperature TN in each compound clearly show the effects of the spin-flop near 20 kG. Effects due to domain realignment are observed below 5 kG for the field normal to the c axis. In the paramagnetic phase above TN the magnetostrictive behavior conforms to a simple model in which the intrachain exchange J is a function of the c parameter. The resulting partial Grüneisen parameter γm∥ =−d(ln J)/d(ln c) for each compound is compared with that derived from thermal expansion measurements.
Hysteresis effects in the critical behavior of a d=3 Ising random field system
Authors: Rezende S. M. , King A. R. , Jaccarino V.
Published: February 2003

A new capacitance (C) technique has been used to study the critical behavior of a randomly diluted, d=3 Ising antiferromagnet as a function of field H, applied colinearly to the c axis. Measurements on Fe0.68Zn0.32F2 confirm that the phase transition remains sharp when H≠0, as was previously concluded from birefringence (Δn) studies. Unlike the d(Δn)/dT vs T results, the measurements of dC/dT vs T show pronounced hysteretic effects in the immediate vicinity of Tc, associated with the particular field-temperature cycling process. This irreversible behavior is attributed to field-induced, domain nucleation. Preliminary dilatometric results indicate that anomalously large changes in c (and/or a) occur close to Tc when H≠0. The relation of the latter to the studies of d(Δn)/dT, dC/dT and other experimental work on the random field problem is discussed.
Random Ising models: Convergence of successive approximations towards exact results
Authors: Benyoussef A. , Boccara N.
Published: February 2003

We studied a new and simple method which gives successive approximate expressions for the magnetization (or any order parameter) of a random Ising model as a function of temperature, site, or bond dilution, frustration, magnetic field,... To obtain the various approximations a trace is performed on finite clusters increasing in size. In particular, we investigated a honeycomb Ising model with random nearest-neighbor interactions and calculated sequences of critical temperatures, percolation thresholds,... which converge towards exact known results.
Potts model of magnetism (invited)
Authors: Wu F. Y.
Published: February 2003

The Potts model is a generalization of the Ising model of magnetism to more-than-two components. First considered by Potts in 1952, the problem has aroused considerable interest in recent years. It has been shown that the model is very rich in its content and, in addition, the extra degree of freedom exhibited by the number of components permits the model to be realized in a wide range of physical systems. In this paper we review those aspects of the Potts model related to its contents as a model of magnetism, focusing particular attention to the results obtained since a previous review was written. Topics reviewed include the upper and lower critical dimensionalities, critical properties, and some exact and rigorous results, for both the ferromagnetic and antiferromagnetic models.
The specific heat of planar spin models
Authors: Ferer M. , Aidinejad A. Hamid , Velgakis M. J.
Published: February 2003

In an attempt to understand the discrepancy between renormalization group predictions of a rounded specific heat peak about 38% above the Kosterlitz–Thouless transition temperature Tc and Monte-Carlo results indicating a sharp peak about 7% above Tc, we have undertaken an analysis of our thirteenth-order, high-temperature series for the free energy of the XY model on the triangular lattice. We have performed N fits on our free energy series in order to estimate the dominant singularity. These results are not consistent with either F≂ξ−2 or a transition at temperatures above Tc. Using these estimates of the leading singularity, we have extrapolated partial sums of our specific heat series for temperatures above Tc, thereby locating the specific heat peak.
Transverse susceptibility of easy-axis ferromagnets near T
C
Authors: Suter R. M. , Karnezos M. , Friedberg S. A.
Published: February 2003

We study the temperature dependence of the zero field transverse susceptibility χ⊥ of NiZrF6⋅6H2O and three isostructural compounds, NiMF6⋅6H2O with M=Si, Ti, Sn. Since these materials are easy axis ferromagnets, χ⊥ is a nonordering susceptibility. Thus, in mean field theory χ⊥ is at most weakly temperature dependent near TC, but in theories including fluctuations, χ⊥ is predicted to have cusp-like behavior at TC. All the compounds studied here have peaks in χ⊥ in the neighborhood of TC. We find that, in the most Ising-like case, NiZrF6⋅6H2O, the first fluctuation term in a 1/z expansion, with z being the number of nearest neighbors, provides a good fit to the data. Even in the less-anisotropic cases, this procedure is qualitatively satisfactory.
Magnetoelastic effects in ferromagnetic resonance
Authors: Tyagi Somdev
Published: February 2003

Ferromagnetic resonance (FMR) at ∼9.4 GHz as a function of hydrostatic pressure to about 10 kbars and uniaxial stress has been studied in two amorphous alloys, Metglas 2826 (Fe40Ni40P14B6) and 2826B (Fe29Ni49P14B6Si2). The pressure dependence of g and the saturation magnetization, Ms has been determined from the hydrostatic pressure dependent FMR measurements, while the stress-induced changes in the FMR line positions have been used to determine the linear saturation magnetostriction coefficient λs.
Fluctuations of the magnetic field generated by permanent magnets
Authors: Schloemann Ernst
Published: February 2003

The short-term stability of the magnetic field generated by permanent magnets is calculated on the basis of spin-wave theory. The results indicate that the relative rms fluctuation of the magnetic field is inversely proportional to V1/2H1/4e , where V is the magnet volume and He the effective magnetic field inside the magnet. For SmCo5 at room temperature the relative rms fluctuation of the magnetic field is calculated to be approximately 0.2×10−11 for V=1 cm3, and He =240 kOe.
Single crystal susceptibility measurements on CuCl2⋅2DMSO, A 1-D S=1/2 quasi-Heisenberg antiferromagnet
Authors: Landee C. P. , Lamas A. C. , Greeney R. E. , Gahlawat P. S.
Published: February 2003

We report the results of magnetic susceptibility investigations of single crystals of CuCl2⋅2DMSO and of a polycrystalline sample of CuBr2⋅2DMSO, [DMSO=(CH3)2SO] two isostructural, orthorhombic linear chain S=1/2 compounds. The principal susceptibilities of the chloride all show rounded maxima near 11 K, then gradually decrease at different rates at lower temperatures. There is no indication of long range ordering above 2 K. All three susceptibilities show evidence of uniaxial anisotropy contributions within the exchange Hamiltonian with the b axis corresponding to the magnetic easy axis. The data are interpreted in terms of the results of Bücher and Honerkamp with an antiferromagnetic exchange constant of −8.2 K and 10% Ising-like anisotropy. The susceptibility of the bromide can be described as a Heisenberg antiferromagnetic chain with J/k=−11.0(2) K above 40 K but at lower temperatures the susceptibility rises as if 7% of the moments were paramagnetic. Since this behavior is observed in different batches, it may have its origin in spin canting.
Susceptibilities of the diluted simple-cubic S=1/2 X
Y antiferromagnet: [Co1−xZnx(C5H5NO)6](NO3)2 (abstract)
Authors: Carlin Richard L. , Lambrecht A. , Burriel R.
Published: February 2003

The specific heat [J. Bartolme, H. A. Algra, L. J. de Jongh, and R. L. Carlin, Physica B 94, 60 (1978)] and ac susceptibility [A. van der Bilt, K. O. Joung, R. L. Carlin, and L. J. de Jongh, Phys. Rev. B 24, 445 (1981)] of [Co(C5H5NO)6](NO3)2 and the specific heat of the zinc-diluted perchlorate analog [H. A. Algra, L. J. de Jongh, and J. Reedijk, Phys. Rev. Lett. 42, 606 (1979)] have previously been reported and analyzed in terms of the XY magnetic model. New data on the zero-field ac susceptibilities of single crystals of diluted [Co1−xZnx(C5H5NO)6](NO3)2 will be reported for 0.19<x<0.87. A phenomenological interpretation of data will be presented.
V/Fe composition-modulated structures
Authors: Wong H. K. , Yang H. Q. , Jin B. Y. , Shen Y. H. , Cao W. Z. , Ketterson J. B. , Hilliard J. E.
Published: February 2003

V/Fe composition-modulated structures have been grown on the (0001) surface of a sapphire substrate in an UHV evaporator. X-ray θ-2θ scans showed that the samples had a bcc (110) texture with a strong composition modulation. Samples with three atomic planes of Fe separated by thick layers of V showed a linear temperature dependence of the saturation magnetization over the range 5–400 K. This behavior is expected for the Bloch spin wave contribution to the magnetization of a 2D ferromagnet. Hysteresis measurements also confirmed that the samples were ferromagnetic. Superconductivity has been seen in samples with very thick V layers.
Magnetic properties of iron-implanted graphite
Authors: Koon N. C. , Pehrsson P. , Weber D. , Schindler A. I.
Published: February 2003

We have measured the magnetic properties of highly oriented pyrolytic graphite (HOPG) implanted with fluences of 25-keV iron atoms ranging from 1016 to 1017 atoms/cm2. The lowest fluence specimen was paramagnetic down to 2 K, with evidence for clusters of only a few spins, while the highest fluence specimen was clearly ferromagnetic, with magnetization curves resembling those of a set of randomly oriented soft magnetic planes. The critical fluence for formation of a ferromagnetic state appears to be between 1 and 3×1016 atoms/cm2 at 25 keV. These results can be qualitatively understood based on the critical density for percolation of near neighbor exchange interactions.
Surface anisotropy effects in the spontaneous magnetization of a semi-infinite ferromagnet (abstract)
Authors: Rado George T.
Published: February 2003

An early theory1 of the temperature and position dependence of the spontaneous magnetization near the surface of a semi-infinite ferromagnet is generalized by including the effects of surface anisotropy. Using the surface anisotropy constants Ks and Kss defined [G. T. Rado, Phys. Rev. B 26, 295 (1982)] for a {110} surface of a bcc crystal, we find that for Ks≠0, Kss≠0 the excitations at low temperatures are combined volume and surface spin waves and that at the ferromagnetic surface the deviation M0−MT of the spontaneous magnetization at temperature T from its value at 0 °K is proportional to T3/2. Such a T dependence was obtained previously1 for Ks=Kss =0 on the basis of the pure volume waves. Next we refine the conditions2 under which the entire early theory1 remains valid when Ks≠0 and Kss≠0. Finally, we consider the special case Ks =0, Kss>0 and predict that here volume and surface spin waves (both are thermally excited) can exist independently and that at the ferromagnetic surface the T dependence of M0−MT has a T3/2 component due to volume waves but a quasilinear component due to surface waves. No quasilinear component of the T dependence at the surface of a semi-infinite ferromagnet at low T has been predicted previously. Because of the lack of existing evidence for the (effective) surface anisotropy determining the type of T dependence of M0−MT at a ferromagnetic surface, the present theory may help explain why the experimentally observed3 T dependence at a {110} Fe surface is proportional T3/2 when the Fe is covered with Ag but quasilinear when it is covered with MnF2. A full account of this work will be published elsewhere.
MSFVW beam steering and spreading over large path lengths
Authors: Floyd R. E. , Sethares J. C.
Published: February 2003

The propagation characterisics of magnetostatic forward volume waves (MSFVW) have been investigated in the 2–6 GHz range. The waves were propagated in 2-in. diameter YIG La-doped films of varying thickness (20, 30, 40 μm). The waves were launched by microstrip transducers on an alumina substrate. Receiver transducers were also on the substrate, but placed 1 in. away, in a semicircle with 10° between each of them. Network analyzer measurements were taken of the devices, and comparisons of output channels show that there is a wide spreading of the MSFVW beam, especially the longer wavelengths. The films also exhibited some natural beam steering. The channel which exhibited the least insertion loss was not always the channel parallel to the input. In an attempt to improve beam spreading, a Permalloy technique was used for concentrating dc fields. With this technique the main beam could be guided to either of two receiving transducers. Results have also been obtained for oblique incidence of these volume waves on a closely spaced metallized surface. Some steering effects due to boundary conditions were found. This effect may have device applications for frequency selective steering.
Temperature dependent magnetic properties of the 1.2-μm bubble diameter compositions (La,Sm,Lu,Tm)3(Fe,Ga)5O12 and (La,Sm,Lu,Tm,Ca)3(Fe,Ge)5O12
Authors: Gualtieri D. M. , Tumelty P. F.
Published: February 2003

Magnetic garnet films of composition (La,Sm,Lu,Tm)3(Fe,Ga)5O12 and (La,Sm,Lu,Tm,Ca)3 (Fe,Ge)5O12 were grown on (111)-oriented substrates of Gd3Ga5O12 to meet a typical as-grown room-temperature specification for a device utilizing bubbles of 1.2-μm nominal diameter: 0.90–1.30 μm thickness, 1.00–1.40 μm stripe width, 300–350 Oe collapse field, 1800–2200 Oe anisotropy field, Q>2.8, film/substrate lattice constant mismatch <0.3 pm, and the magnitude of the temperature coefficient of the bubble collapse field measured at 50 °C between 0.21% and 0.23% °C−1. Films were grown at about 960 °C from a PbO/B2O3 flux using the isothermal dipping technique with rotation. Growth rate was adjusted in the range 0.40–0.95 μm min−1 to attain a desired characteristic length of 0.130–0.145 μm. The role of Tm is to reduce the magnetization at a given Curie temperature, which allows films to be grown at a Curie temperature of 470 K and a magnetization of 680 G for the Ga-substituted composition, and a Curie temperature of 493 K and a magnetization of 660 G for the (Ca,Ge)-substituted composition. Film properties were measured over a temperature range of −20 to +100 °C by optical and FMR techniques. The temperature coefficient of the anisotropy field is nearly constant from −20 to +100 °C and has a value of about −0.7% °C−1 in both compositions.
Effective mobility limit in small-bubble, low-damping bubble materials
Authors: Slusky S. E. G. , Ballintine J. E.
Published: February 2003

Examination of the implications of the basic equations that govern the motion of bubbles with nonzero winding number (S) yields an unexpected result. Bubble velocity is limited to the speed implied by the effective wall mobility γr/2S, no matter how large the actual wall mobility. For large bubbles, this limit will not usually be significant. However, for small bubbles (r less than 1 μm) in low-damping materials, this limit will profoundly affect the bubble motion. We present a derivation of the effect and experimental confirmation of it.
Dysprosium containing bubble garnet composition for ion-implanted contiguous disk devices
Authors: Makino H. , Okada O. , Hidaka Y.
Published: February 2003

A new bubble garnet composition containing dysprosium (DySmLuBiCa)3(FeGe)5O12 has been investigated for use in 4-μm period ion-implanted contiguous disk (CD) devices. The most significant property of the material is its low value of difference in magnetostriction constants, δλ(=λ100−λ111=+1.4×10−6). The low δλ is attained by substituting Dy ions into the dodecahedral sites. The Gilbert damping parameter α is moderate. The present Dy-containing garnet showed several favorable characteristics with respect to bubble propagation in 4-μm period He+ implanted CD devices. Those characteristics are (1) small minimum drive field, (2) suppression of bubble jumping to adjacent CD ‘‘good’’ tracks, even in 6-μm loop period, (3) smooth followup of bubble positions to drive field directions, and so on. These characteristics in bubble propagation along CD tracks are interpreted by the in-plane magnetization reversal at the pattern edge, which is related to δλ and stress relief. Smaller δλ decreases threefold symmetric behavior of charged wall movement along pattern edges.
High Curie temperature drive layer materials for ion-implanted magnetic bubble devices
Authors: Fratello V. J. , Wolfe R. , Blank S. L. , Nelson T. J.
Published: February 2003

Ion implantation of bubble garnets can lower the Curie temperature by 70 °C or more, thus limiting high temperature operation of devices with ion-implanted propagation patterns. Therefore, we made double-layer materials with a conventional 2-μm bubble storage layer capped by an ion-implantable drive layer of high Curie temperature, high magnetostriction material. Contiguous disk test patterns were implanted with varying doses of a typical triple implant. Quality of propagation was judged by quasistatic tests on 8-μm period major and minor loops. Variations of magnetization, uniaxial anisotropy, implant dose, and magnetostriction were investigated to ensure optimum flux matching, good charged wall coupling, and wide operating margins. The most successful drive layer compositions were in the systems (SmDyLuCa)3 (FeSi)5O12 and (BiGdTmCa)3(FeSi)5O12 and had Curie temperatures 25–44 °C higher than the storage layers.
Temperature dependence of anisotropy fields in deuterium implanted garnet films
Authors: Krafft C. S. , Kryder M. H.
Published: February 2003

The total implantation-induced uniaxial anisotropy field change ΔHE, and that portion attributed to the magnetostriction ΔHσ have been measured in deuterium implanted garnet films from 20 to 180 °C. No saturation in ΔHE was observed for the highest strain measured, 2.2%. ΔHE and ΔHσ were found to decrease nearly linearly with increasing temperature. The ratio ΔHσ/ΔHE was approximately 0.4. In films which were implanted with doses up to 1×1016 D+2/cm2,4πMs(I) decreased more than λ111(I) relative to their nonimplanted values, although λ111(I) decreased faster than 4πMs(I). The quantity λ111/Ms(B) in the bulk and λ111/Ms(I) in the implanted layer had different temperature dependences, which depended on the amount of implant-induced damage.
Mössbauer study of H+ and Ne+ implanted YIG
Authors: Marest G. , Perez A. , Ponthenier J. L. , Gerard P. , Robertson J. M.
Published: February 2003

Conversion electron Mössbauer spectroscopy (CEMS) measurements have been performed on Y3Fe5O12 (YIG) enriched by 25%57Fe. Samples were implanted with H+ and Ne+, respectively. For the hydrogen implantation, two kinds of samples were used, one with a thin SiO2 layer and the other without this layer. A comparison of the H+ and Ne+ as implanted samples has confirmed the anomalous character of the H+ implantation. The study of the influence of the presence or not of the silica layer is still a pending problem.
High sensitivity apparatus for low optical absorption measurements
Authors: Nistor L. C. , Nistor S. V. , Teodorescu V.
Published: February 2003

The paper describes a laser calorimetric apparatus constructed and calibrated for measuring very low absorption coefficients of transparent materials. By using miniature thermistors as temperature sensors the sensitivity has been increased by at least two orders of magnitude compared with thermocouple calorimetry. Such a high sensitivity opens new experimental possibilities, like performing absorption measurements on highly transparent materials with low power cw lasers or with a single laser shot in the pulsed regime.
Frequency control of an optically pumped Na2 laser
Authors: Man C. N. , Brillet A.
Published: February 2003

The electronic control of a Na2 dimer laser and of its argon-ion pump is described. This leads to an extremely narrow emission linewidth (less than 200 Hz) as well as a good amplitude stability and a tunability of a few GHz around each line center.
Linear electro-optic effects in zincblende-type semiconductors: Key properties of InGaAsP relevant to device design
Authors: Adachi Sadao , Oe Kunishige
Published: February 2003

General expressions are derived for the dispersion of linear electro-optic coefficients in terms of electric-field-induced modulations of the electronic energy-band structures. The theoretical predictions are compared with existing linear electro-optic dispersion data in materials of a number of the II-VI and III-V binary compounds below the direct-band edge. It is found that the calculations show a quite good agreement with these experimental data. This model is applied to In1−x Gax Asy P1−y quaternaries lattice matched to InP. The dispersion of the nonlinear optical (optical rectification) coefficients is also obtained on the basis of this model. The present results allow us to design a wide variety of optoelectronic devices.
Some parametrizations useful for determining the specific surfaces and the angularities of amorphous samples
Authors: Ciccariello S.
Published: February 2003

The conditions which must be met by any parametrization of the correlation function of amorphous samples so that it can be physically consistent are briefly discussed. Three examples are explicitly worked out. They correspond to simple analytical expressions both for the correlation function and for the scattered intensity. They are used for determining the specific surfaces and the angularities of some two-component samples already analyzed using standard procedures. The results are satisfactory and indicate that the aforesaid parametrizations could be successfully used also in the case of three-component samples.
Limitation of accelerating process in the partly neutralized relativistic electron hollow beam
Authors: Chen H. C.
Published: February 2003

A fluid-Maxwell thoery of the diocotron instability is developed for a relativistic electron hollow beam which is assumed in rigid-rotor and cold laminar flow equilibria. Stability analysis is performed for a sharp boundary electron density profile including the influence of positive ions which can accumulate in a long pulse device, and which form a partially neutralizing background. In the case of the strong magnetic field and tenuous electron beam (plasma frequency ωpb ≪gyrofrequency ωc) a partially neutralizing ion background staying uniformly within the beam annulus (R1<r<R2) has a stabilizing effect on the diocotron instability, R1 and R2 are the inner and outer radius of the annular hollow beam, respectively. However, the ions accumulating in the center of the beam (0<r<R1) have a destabilizing effect on the diocotron instability. Most importantly the kink mode becomes unstable with a growth rate several tenths of the diocotron frequency ωD ≡ ω2pb/2γ2ωc, where γ is the relativistic scaling factor.
Scattering of electromagnetic waves from a randomly perturbed quasiperiodic surface
Authors: Shin R. T. , Kong J. A.
Published: February 2003

The scattering of electromagnetic waves from a randomly perturbed quasiperiodic surface is studied for active remote sensing of plowed fields. The Kirchoff approximation is used. The narrow-band Gaussian random variation around the spatial frequency of the sinusoidal variation is used to introduce the quasiperiodicity. The physical optics integral is evaluated to obtain closed form solutions for coherent and incoherent bistatic scattering coefficients. In the geometrical optics limit, it is shown that the bistatic scattering coefficients are proportional to the probability of the occurrence of the slopes which will specularly reflect the incident wave to the observation direction. The theoretical results are illustrated for the various cases by plotting backscattering cross sections as a function of the angle of incidence. It is shown that there is a large difference between the cases where the incident wave vector is parallel or perpendicular to the row direction. When the incident wave vector is perpendicular to the row direction, the maximum value of the backscattering cross section does not necessary occur at normal incidence. The scattering coefficients can be interpreted as a convolution of the scattering patterns for the sinusoidal and the random rough surfaces. For the backscattering cross sections we observe the occurrence of peaks whose relative magnitudes and the locations are explained in terms of the scattering patterns for sinusoidal surfaces.
Frequency dependence of the pulsed high-pressure sodium arc spectrum
Authors: Dakin James T. , Rautenberg Theodore H.
Published: February 2003

Spectral energy distributions are calculated and measured for a wall-stabilized high-pressure Na-Hg-Xe arc in pulsed operation. These and other quantities are studied as a function of the pulsing frequency over the range 500–5000 Hz, and as a function of duty cycle over the range 25%–100% for a fixed power input of 150 W. The arc is contained in a 5.5-mm-diam channel with an electrode separation of 39 mm containing a gas mixture of 100-Torr Na, 470-Torr Hg, and 190-Torr Xe. The fully time-dependent energy balance model assumes local thermodynamic equilibrium and one-dimensional cylindrical symmetry. The radiation transport calculation includes the effects of 28 Na lines in the visible and infrared, 20 of which are treated as optically thick. The amount of nonresonance Na radiation in the spectrum is found to be maximum at the lowest frequency and duty cycle. Under these conditions the model shows the arc center temperature to be lowest prior to the pulse, but to reach the highest peak values well before the end of the power pulse.
Collapse of multiple gas bubbles by a shock wave and induced impulsive pressure
Authors: Tomita Yukio , Shima Akira , Ohno Takashi
Published: February 2003

The problem of bubble-bubble interaction is studied experimentally. The motions of multiple gas bubbles attached to a solid wall by a shock wave are observed by using a high speed camera, and the induced impulsive pressures are measured. On the basis of these results, the effects of number and configuration of gas bubbles on the collapsing process and the impulsive pressure are clarified. The maximum impulsive pressure quickly decreases with reducing the interval beteween bubbles due to significant interaction. The direction of a liquid jet formed within a bubble is determined as a resultant of effects such as shock direction, shock strength, and interactions between bubbles and between a bubble and a solid wall.
Multiple scattering formalism: Application to scattering by two spheres
Authors: Domany Eytan , Entin-Wohlman Ora , Mizrachi Leah
Published: February 2003

We present a multiple scattering formalism that was developed in order to calculate elastic wave scattering by complex defects. The formalism is based on an expansion of the T matrix in terms of single scatterer T matrices; we include all single and double scattering processes. The method has been numerically implemented for the case of two spherical cavities; the interaction terms were found to be small, which indicates that other problems of interest, such as a subsurface spherical cavity or crack can also be treated.
Application of multiple scattering theory to subsurface defects
Authors: Domany Eytan , Entin-Wohlman Ora
Published: February 2003

A recently developed multiple scattering formalism is applied to treat scattering of elastic waves by subsurface defects. In particular, the problem of a spherical cavity near a stress-free surface is treated.
Enhanced growth mechanism and superconducting properties of V3Si layers formed by sputter-deposited V films on SiO2 substrates
Authors: Oya Gin-ichiro , Akada Katsuhiro , Kazumi Jiro , Sawada Yasuji , Onodera Yutaka
Published: February 2003

An enhanced growth of V3Si layers by rf-sputter deposition of V films on fused silica substrates held at temperatures between ∼350 and ∼850 °C has been found. The growth rate at 500 °C shows a (time)1/2 dependence and is as high as ∼1.8×10−14 cm2/sec. The activation energy is estimated to be as low as ∼1 eV. The enhanced growth is attributed to the formation of intermediate V-Si-O layers and to the presence of lattice defects induced in the V films by the sputter-deposition process. The superconducting transition onset temperatures of the V3Si increases with increasing thickness up to 16.9 K. The layers formed at 500 and at 600 °C have critical current densities of (2–7)×105 A/cm2 at 4.2 K in applied magnetic fields lower than 35 kOe. These layers show different angular dependences of critical currents with respect to field direction. This difference is related to the different growth morphologies of the V3Si layers.
A numerical solution of cylindrical coordinate Laplace’s equation with mixed boundary conditions along the axis of symmetry: Application to intracerebral stimulating electrodes
Authors: Church P. , Leduc A. , Beique R. A. , Derome J. R.
Published: February 2003

A numerical solution method of Laplace’s equation with cylindrical symmetry and mixed boundary conditions along the Z coordinate is presented. The method is based on an iterative process. It is applied to the evaluation of current density distribution in the region surrounding electrodes used for intracerebral electrical stimulations. The procedure converges quickly and after only twelve iterations the boundary conditions are satisfied within an accuracy of 0.1%. The convergence criterion is discussed and the results obtained on the current density distribution are presented.
Damage around the ion path in cellulose triacetate. I. Total evaluation
Authors: Vareille J. C. , Decossas J. L. , Moliton J. P. , Teyssier J. L.
Published: February 2003

Using the ‘‘scavenger technique’’ linked to visible spectroscopy, we evaluate the total number of radicals produced by one ion around its trajectory. This evaluation is achieved by the intermediary of a fictitious cylindrical volume containing all the various radicals likely to be produced whose radius a is determined by means of statistical calculation applied to the spectroscopical results. Then we compare the values of a calculated for various ions with different energies.
Damage around the ion path in cellulose triacetate. II. A track model
Authors: Decossas J. L. , Vareille J. C. , Moliton J. P. , Teyssier J. L.
Published: February 2003

In this paper, a model of an ion track is proposed. It is justified by experimental results obtained by electron microscopy. These results show that a track is composed of two parts: (i) a core in which the material is totally destroyed, and (ii) a ‘‘halo’’ in which the damage decreases when the distance from the ion path increases. The overall results given in paper I and the calculation of deposited energy density of Fain [J. Fain, M. Monnin, and M. Montret, Proceedings of the 8th International Conference on Nuclear Photo., S.S.N.T.D., Bucarest (1972), p. 34, and J. Fain, M. Monnin, and M. Montret, Radiat. Res. 57, 379 (1974)] led us to the volume density of free radicals at every point inside the latent track. The core radius is established for ions of Z≤18 and E≤10 MeV/amu. A great density of damage close to the ion path is shown, and the influence of this phenomenon on track etching is studied.
Consequences of sputtering with molecular ions
Authors: Zalm P. C. , Beckers L. J.
Published: February 2003

According to Sigmund’s linear cascade theory of sputtering, the yield for elemental collision partners is given by Y(E)=Cpt Sn(E/Ept), where Cpt and Ept are characteristic constants depending on projectile and target parameters and Sn is the reduced nuclear stopping. We show that under fairly general assumptions a similar relation holds for the physical sputtering yield of elemental targets bombarded by complex (molecular) ions. The characteristic constants must then be taken as the sum of those of the ion’s constituent particles. Complex ion yields (e.g., of CF+n≤3 on Si) are currently being compared with results for noble gas ions of approximately equal mass. ‘‘Chemical enhancement effects’’ are thus being ‘‘deduced’’ from Reactive Ion Beam Etching (RIBE) experiments. We show that with the proposed model description no such evidence can reliably be extracted from existing RIBE data. Finally, we present sputtering yield data for SO+ ions on Si (0.1–15 keV) at temperatures of 300, 700, and 1100 K to elucidate the above remarks and to show that chemical contributions can, at least partially, be isolated.