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To remove arsenic from water we are developing a research project that applies magnetic separation methods. In order to increase the removal efficiency we are using magnetic aggregates. These magnetic aggregates are iron-based and were all (except for one) prepared by us. In this paper we report the preparation steps and some of the results of the characterization and absorption tests we have performed in order to conclude about its structure and efficiency in what concerns arsenic removal. Index Terms--Arsenic removal, characterization of magnetic materials, iron oxides, magnetic aggregates, magnetic separation, preparation of magnetic materials, testing.

A wide-bored conduction-cooled superconducting magnet with operating current of 116 A is designed, fabricated and tested for the material processing devices. A second-stage GM cryocooler with the second-stage cooling power of 1 W is used to cool the superconducting magnet from room temperature to 4.2 K.

Several different shell types Nb(sub 3)Sn coils are developed and installed in a mirror magnet configuration and tested at Fermilab. The results show that the previously suspect splice technique is adequate and is not responsible for the quench performance limitation.

The main quadrupole magnets in the Q1 (LQXA) and Q3 (LQXC) assemblies are MQXA elements designed and fabricated by KEK and Toshiba, while those in the Q2 (LQXB) assemblies are MQXB quadrupoles designed and fabricated by Fremilab. The cold test results of LQXB02 and an overview of the magnetic measurements results of the cold masses built up to date are presented.

The transition from a ferromagnetic to a superparamagnetic regime has been studied in a Cr-containing FINEMET-type alloy. Cr enhances the thermal stability of the alloy against nanocrystallization and reduces the Curie temperature of the remaining amorphous phase. Above room temperature, the temperature dependent hysteresis loop of a nanocrystalline sample can be described by a model of interacting superparamagnetic particles. The temperature dependence of the apparent magnetic moment of the particles obtained from the fittings is interpreted in an extended version of the model. Index Terms--Hysteresis, magnetic materials, magnetization processes.

New results on the giant magnetoimpedance effect in soft magnetic amorphous and nanocrystalline wires and microwires are presented. The relation between the magnitude of the effect and the dynamic surface magnetization processes is analyzed. The special role of magnetostriction is discussed with a special emphasis on the possibilities it offers for improving the magnetoimpedance response of wire-shaped materials. Index Terms--Amorphous glass-coated microwires, amorphous wires, giant magnetoimpedance, nanocrystaliine glass-coated microwires, nanocrystalline wires, soft magnetic materials.

This paper presents a tensile stress evaluation of steel plates by chaos of Barkhansen noise. The stress of magnetic materials affects magnetic domains, so the amount of the stress can be evaluated by Barkhansen noise. Barkhausen noise is a very complicated signal, so a special evaluation method is needed to use it. The quantitative change of Barkhausen noise after a tensile stress test can be found by the fractal dimension of the chaotic attractors constructed by the measured Barkhansen noise. Index Terms--Barkhausen noise, chaos, fractal dimension, tensile stress.

Composites have been prepared from Mn-Zn and Fe or [Fe.sub.25][Ni.sub.75] nanostructured powders, by melting in a planetary mill, compaction, and subsequent annealing. A solid state oxido-reduction reaction between iron and ferrite degrades the magnetic properties. On the other hand, Permalloy, which is more resistant to this reaction, results in soft magnetic nanocomposites which possess a magnetization higher than those of good ferrites. Index Terms--Composite media, ferrites, magnetic materials, powders.

We report striking transport behavior of magnetic tunnel junctions which are engineered to incorporate localized magnetic impurities inside the tunnel barrier. Such junctions exhibited zero-bias anomalies (giant conductance dip or equivalently, giant resistance peak) in dynamic conductance curves, and striking bias and temperature dependencies of tunneling magnetoresistance (TMR), i.e., suppression of TMR at zero-bias and the decrease of TMR with decreasing temperature. Logarithmic dependencies of the conductance on bias and temperature agree well with Applebaum's theory describing Kondo-type spin flip scattering between tunneling electrons and impurity spins. The systematic variation of the transport anomalies with oxidation time confirmed that an over-oxidation of the tunnel barrier leads to diffusion of Co (Fe) ions from the bottom electrode into the barrier, which is consistent with the Cabrera-Mott oxidation model. Index Terms--Kondo scattering, magnetic tunnel junction, zero-bias anomalies.

Exchange-biased electrodes IrMn/Ta(2 [Angstrom])/CoFe/ Al[O.sub.x] and IrMn/CoFe/Ta(2 [Angstrom])-Al[O.sub.x] used in a magnetic tunnel junction were annealed at 300[degrees]C to study the Mn diffusion charaeteristics. Auger electron spectroscopy and X-ray photoelectron spectroscopy analysis of the annealed electrodes show that the Ta diffusion barrier effectively blocked the Mn migration, regardless of the barrier location. Also concluded from the study was that the Mn migration is largely enhanced by the preferential oxidation of Mn. Index Terms--Diffusion processes, magnetic materials, tunneling magnetoresistance.

Cobalt dot arrays are fabricated by [Ga.sup.+] ion beam induced chemical vapor deposition (IBICVD) with an objective to explore size limitations. Dots of about 100-150 nm in diameter are obtained as flat islands. Characterization by means of magnetic force microscopy (MFM) and Lorentz transmission electron microscopy (LTEM) show the deposited structures exhibiting ferromagnetic properties. Index Terms--Cobalt, ion beam applications, magnetic materials, nanotechnology.

In this paper a new power supply is proposed to improve the characterization of soft magnetic materials at high flux density. The power supply consists of a high frequency switching power supply (PWM inverter) with a voltage regulator to control the distortion of the e.m.f. induced in the device under test (Epstein yoke, wound, core, etc.). The experimental results confirm the good features of the proposed solution for flux density values up to 1.9-2.1 T.

A magnetic-based nondestructive evaluation (NDE) method, which employs Barkhausen effect and measurement of hysteresis loops, is developed and used to correlate the magnetic and mechanical properties in ultra low carbon (ULC) steel. The NDE test equipment offers the capability to detect small deviations from linearity that occur in the stress-strain curve well below the 0.2% offset strain. Results show that three properties extracted from the experimental results, jumpsum and jumpsum rate (derived from the Barkhausen spectrum), and differential permeability (derived from the B-H loops), vary sensitively with small deformations well below the 0.2% offset strain in ULC steels; however coercivity is a slowly varying function of small applied strains. Index Terms--Barkhasuen effect, jumpsum method, mechanical properties, nondestructive testing.

Multi-segment cores have been developed by cutting standard MnZn ferrite cores into thin segments and then re-assembling the segments together. All the segments were separated by a thin film of air or insulation materials of microscopic dimensions. The core loss properties of these experimental samples have been investigated between the frequencies of 200 kHz to 2 MHz. The real and imaginary parts of the effective permeability have been determined from these measurements. Experiment results show that the multi-segment ferrite cores are effective in reducing the core loss by possible mechanisms of reduction in the internal electromagnetic field strength and of reduction in the influence of the magnetic skin effect. Index Terms--Core loss, dielectric loss, ferrites, skin effect.

Polycrystalline hexagonal ferrites (Y, Z and W-phases) were prepared by the usual ceramic sintering. Their complex permeability spectra were natural resonance type, and numerically separated into spin rotational and domain wall motion components. For the spin rotational component, it was found that the Snoek's product values of them were far beyond the product values of spinel ferrite. It enabled us to design the thin electromagnetic wave absorbers in the quasimicrowave region. Index Terms--Electromagnetic wave absorber, hexagonal ferrite, permeability, Snoek's product.

Grain growth behavior in correlation with magnetic loss has been investigated in Mn-Zn ferrites with the variation of additive content and particle size of the system. The powders of [([Mn.sub.0.76][Zn.sub.0.24]O).sub.0.94] [([Fe.sub.2][O.sub.3]).sub.1.06] composition and the average particle size of 0.94 [micro]m and 1.93 [micro]m are prepared by milling the calcined powder in an attritor. CaO and Si[O.sub.2] are chosen as the additives and their content is varied from 0-5 wt%, respectively. It has been found that the grain morphology and the magnetic loss are greatly dependent upon the amount of additives and the particle size of the system. There is an optimum content of the additives to produce normal grain structure and low magnetic loss. Under a sufficient driving force of the system (approximately, submicron-sized powders), the abnormal (duplex) grain structure is developed in the specimens with the additives in excess of the optimum value. The possible mechanism of such impurity-induced abnormal grain growth is explained from the observed faceted ferrite grains which has been known to have singular surface structure and their growth kinetics controlled by two-dimensional nucleation. It is suggested that the additives content along with particle size control is one of the important processing variables to obtain the low-loss Mn-Zn ferrites with fine and uniform grain structure. Index Terms--Abnormal grain, additives, magnetic loss, Mn-Zn ferrites.

In this paper, FeCoB amorphous thin films were deposited on glass substrates using a triode sputtering source under a uniform applied magnetic field. The as-deposited films exhibit a low coercivity of ~1.7 Oe, a high anisotropy field of ~37 Oe and 4[Pi] [M.sub.s] ~17.5 kG, when sputtered with a bias voltage of 180 V. The large anisotropy fields and saturations in these films result in a ferromagnetic resonance frequency as high as ~2.63 GHz, a relative permeability [micro]' of ~400-500 and a low dissipation [micro]' of 10-30 in the frequency range of 0.1-1 GHz. Upon subsequent annealing at 200-400 [degrees] C for 2 hrs, the magnetic properties of the films are found to be affected significantly. The magnetic properties of the as-deposited and the annealed films have been compared with a considering of the microstructure modification during annealing. Index Terms--UHF properties, soft magnetic properties, amorphous magnetic thin films, Fe-Co-B alloys.

The power loss characteristics of Mn-Zn ferrites were observed up to 1 MHz at 25 mT as a function of temperature. At 100 kHz the temperature at which the power loss minimum occurred was near 70 [degrees] C, at 500 kHz 50 [degrees] C and at 1 MHz even lower. The contribution of eddy current loss to the temperature dependence of the total power loss was negligibly small at 1 MHz because the resistivity is independent of temperature. The contribution of the residual loss due to magnetic rotation was significant and strongly temperature dependent at 1 MHz. The frequency where the residual loss starts to increase was in good agreement with the onset frequency of dissipation of the complex permeability. Index Terms--Mn-Zn ferrites, hysteresis loss, eddy current loss, residual loss.

We have systematically investigated the microstructural effects including grain size, precipitation, and structural order parameter on the high temperature magnetic and mechanical properties of FeCo-based commercial alloys. At high temperatures the equilibrium nonmagnetic precipitates significantly deteriorate the soft magnetic properties. Poor mechanical properties are mainly due to the nature of the ordered structure of FeCo alloys. Based on this understanding we have designed new magnetic composites by reinforcing FeCo alloys with high strength fibers. The magnetic and mechanical properties can thus be improved independently through optimizing the magnetic matrix and fiber network, respectively. These new magnetic composites show excellent soft magnetic and mechanical properties. In particularly, negligible creep has been observed at 600 [degrees] C. Index Terms--Magnetic composites magnetocrystalline anisotropy, soft magnetic materials, soft magnets.

The trend in both military and commercial markets for greater affordability has prompted the electromechanical designer toward higher speed and higher operating temperature devices. New magnetic materials are essential for the success of many of these power generation, distribution, and utilization systems. This manuscript briefly describes some of the applications for advanced high temperature magnets. Index Terms--Aerospace, electromechanical machines, high temperature, more electric aircraft.

A setup designed to measure the high frequency permeability of soft ferrite material under stress is presented. It is based on a coaxial cell, and allows measurements up to 6 GHz. Specific calculations are used to take into account the modifications in the line geometry and it is shown that the presented measurement technique maintains accuracy and robustness. Permeability spectra of soft [Ni.sub.0.48][Zn.sub.0.52] ferrite under quasi uniaxial parallel compressive stress illustrate the method. Index Terms--Magnetostriction, ferrite, high-frequency permeability, stress.

Giant Magnetostriction (GMS) reported until now in thin films using rare earth-transition metal [RM.sub.2] (R = Tb, Sm, and M = Fe, Co) compounds, presents in most of cases an isotropic or quasi-isotropic magnetoelastic (ME) behavior. A large change of the ME coefficient b under the lowest possible external field is required in order to improve the sensitivity of these materials which are interesting for their application in the microelectromechanical systems (MEMS). The present paper shows the possibility of improving strongly both the ME coefficient and sensitivity. Optimized ME properties are correlated with the sputtering parameters such as the RF power [P.sub.rf] and the sputtering gas pressure [P.sub.Ar]. The magnetostriction increases with [P.sub.rf] up to very large saturation values not observed until now in TbFe films ([Delta]l/l = 1300 ppm or [b.sup.[Gamma],2] = 50 MPa at 20 kOe) due to a structural change from amorphous at low [P.sub.rf] to crystallized phase at a high [P.sub.rf] as confirmed from XRD. When a bias magnetic field [H.sub.d] is applied on the film during deposition it is observed a strong change in the structural, elastic, magnetic and ME properties. [H.sub.d] keeps the amorphous phase even at high [P.sub.rf] which induces a reduction of the ME 'linewidth' but an increase of the GMS sensitivity. Index Terms--Thin films, Laves phases, giant magnetostriction, magnetoelastic sensitivity.

Composites of Terfenol-D with metal binders were produced by explosive compaction. Compacts produced from powders prepared this way had a soft phase and intimate contact and bonding between particles are achieved. [M.sub.s]/volume follows the expected trend based on the separate [M.sub.s]/volume values of the constituents added. Magnetostriction of compacts made from mixture of Cu coated terfenol-D powder and Cu powder at a compressive stress of about 18 MPa were 110 x [10.sup.-6] and 195 x [10.sup.-6] prior to and after stress relief anneal at 350 [degrees] C. This value is about 18% of that obtained with Terfenol-D. Magnetic alignment of powder during compaction can increase this to levels obtained in Terfenol-D-polymer composites. These composites had Young's moduli values in the range of 33-36 GPa and were strong and tough enough to withstand machining operation. Index Terms--Terfenol-D, magnetostrictive composites, metal binder, dynamic compaction.

We present a useful technique to calculate the magnetic response of hard magnetic materials to the application of magnetic fields. We consider that these materials can be described by means of Preisach-based models and the parameters defining the material are distributed according to a Gaussian function. We find that the utilization of a grid in a 'cobweb' style can help us to improve both accuracy and speed for this kind of simulations. We show the usefulness of this grid by solving in an easy way inverse type problems. Index Terms--Cobweb grid, hard magnetic materials, hysteresis modeling Preisach models.

Permalloy ([Ni.sub.80][Fe.sub.20]) wire-based structures (30 nm thick and 1 [multiplied by] w [multiplied by] 10 [micro]m wide) with junctions (crosses, networks, H-shapes, rectangular chains and ring chains) prepared on a GaAs (100) substrate were observed in both their demagnetized and remanent states by magnetic force microscopy (MFM) in order to investigate the role of junction geometry in domain formation. Except in ring chains, two classes of domain configuration are found at the junction: (i) a domain wall-like feature due to abrupt spin rotation and (ii) a triangle-shape domain consistent with a flux closure configuration. Ring chains, on the other hand, form vortex domains at every other junction. The MFM observations are compared with micromagnetic calculations which qualitatively support the magnetic domain configurations. Index Terms--Mesoscopic structures, magnetic domain configuration, magnetic force microscopy, micromagnetic calculation.

The effects of tensile stress and strain on magnetization and magnetic domains in silicon steel sheets were investigated. The strain-magnetization properties of plastic deformation regions under stress showed peculiar characteristics. We observed lancet domains in a sample after removing plastic stress, and found that the appearance of lancet domains was the cause of peculiar stress magnetization characteristics. Index Terms--Domain, lancet, magnetization, silicon iron.

We report variations in the coercivity of Co[Fe.sub.2][O.sub.4] nanoparticles as a function of particle size, temperature and light intensity. For 30 nm particles, this change in was 2300 Oe at 10K, 120 Oe at 170K, for a light intensity of under 2 milliwatts. The remanent magnetization was nearly unchanged by illumination. A simple model of optical absorption followed by electron transfer between [Co.sup.2+] and [Fe.sup.3+] ions is proposed. Index Terms--Cobalt ferrite, coercivity, photomagnetic effect, remanent magnetization.

We report on the domain wall magnetoresistance of Co and Ni nanowires of 45 nm on diameter or less. The enhancement of the resistance due to an isolated domain wall is clearly evidenced from magnetoresistance hysteresis loops obtained under parallel and perpendicular fields. The domain walls magnetoresistance effect is by one order of magnitude smaller in Ni than in Co and it was observed only at low temperature for Ni nanowires. The formation and motion of domain walls is demonstrated by MFM experiments. Index Terms--Domain wall magnetoresistance, spin relaxation, magnetic nanowire, magnetic structure imaging.

Pulsed-current controlled wall motion in 20 [micro]m wide x 200 [micro]m long x 160 nm thick patterned Permalloy strips was studied using magnetic force microscopy. By sequential imaging, the displacement of Bloch walls as far as 200 [micro]m along the strip was observed. The direction of motion was in the same direction as the carrier velocity, which reversed with current polarity. The displacement per pulse was dependent upon the sample thickness and current density, which suggests that the mechanism is a combination of s-d exchange and hydromagnetic domain drag forces. Index Terms--Permalloy, current pulse, domains, Bloch wall, s-d exchange, domain drag, MFM, magnetization switching.

The enhancement in signal-to-noise ratio and lateral resolution in MFM in going from ambient pressure to UHV is demonstrated. The performance of several cantilevers is evaluated using a patterned 50 nm thick permalloy film, with cross-tie as well as ~90 [degrees] domain walls, and a 200 nm thick permalioy film with perpendicular magnetization. The increase in the quality factor of the cantilever oscillation in UHV improves the sensitivity, consequently allowing less magnetic material on the tip to achieve the same signal-to-noise ratio. This reduction in magnetic volume sharpens the lateral resolution. We also demonstrate that the magnetic interaction can be so weak that a magnetic contrast is visible only under UHV conditions. Index Terms--Magnetic force microscopy, resolution, UHV.

The purpose of this paper is to present the results of stress damage observation using a new sensor and a high performance eddy current testing system. Selected digital signal processing algorithms were applied in order to enhance the obtained signals and extract parameters suitable for quantitative stress evaluation. The experimental verification of the developed technique is done and the selected results are presented. Index Terms--Nondestructive eddy current testing, magnetic sensors, iron based material, stress degradation evaluation.

The micromagnetic properties of a soft underlayer in perpendicular media are studied. It is shown that stray fields from a recording layer can substantially modify magnetic properties of soft underlayer material. The degree of modification is determined by the characteristic bit size in the recording layer and by the soft underlayer material magnetic characteristics. It is found that there exists a thin layer within a soft underlayer with reduced permeability. The effects of the presence of such a reduced permeability region within a soft underlayer on both reading and writing processes are discussed.

Analytical magnetic force microscopy has been applied to investigate the relationship between the soft magnetic underlayer and the microscopic magnetization structures of double layered perpendicular media. The magnetization structures of the CoCrPtTa perpendicular media with Co-Nb-Zr, Co-Ta-Zr, Fe-Ta-C, and Fe-Al-Si soft magnetic underlayers are compared. The medium with Co-Ta-Zr underlayer shows low medium noise and high resolution characteristics at high recording densities. The magnetization irregularities of perpendicular media are strongly affected by the soft magnetic underlayer material. Index Terms--Magnetization structure, perpendicular media, soft magnetic underlayer.

The purpose of this paper is to introduce a new eddy-current testing technique for surface or near-surface defect detection in nonmagnetic metals using giant magnetoresistive (GMR) sensors. It is shown that GMR-based eddy-current probes are able to accurately detect short surface-breaking cracks in conductive materials. The self-rectifying property of the GMR sensor used in this study leads to a simplified signal conditioning circuit, which can be fully integrated on a silicon chip with the GMR sensor. The ability to manufacture probes having small dimensions and high sensitivity (220 mV/mT) to low magnetic fields over a broad frequency range (from dc up to 1 MHz) enhances the spatial resolution of such an eddy-current testing (ECT) probe. Experimental results obtained by scanning two different probes over a slotted aluminum specimen are presented. General performance characteristics are demonstrated by measurements of surface and subsurface defects of different sizes and geometries. Dependence of the sensor output on orientation, liftoff distance, and excitation intensity is also investigated. Index Terms--Crack detection, eddy-current testing, giant magnetoresistance (GMR), magnetic sensors.