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The generalization of the Hilbert transform for three-dimensional magnetic fields in magnetic recording is presented. This generalization is based on the simultaneous use of 'magnetic charge' and 'electric current' models of the recording media. The Fourier representation of the 2-D Hilbert transform is discussed, along with its unique scaling properties. Index Terms--Fourier transform, Hilbert transform, magnetic recording, scaling.

The behavior of magnetoresistance in NiFe (permalloy) point junctions was investigated using an STM set-up, where the junction resistance was continuously varied from [10.sup.8] [OMEGA]-[10.sup.3] [OMEGA]. Our results reveal an enhancement of magnetoresistance of more than 80% at one conductance quantum, and the decaying magnetoresistance as one moves away from 12.9 k[OMEGA] to either the diffusive regime or the tunneling regime, as supported by independent theories on spin-dependent transport. The suppression of magnetoresistance with incorporation of a 35-nm-thick Au barrier was observed, as well as the dependence of magnetoreslstance on the relative orientations of the electrodes. Index Terms--Ballistic magnetoresistanee, magnetoresistance, scanning tunneling microscope (STM).

The switching characteristics of submicron permalloy elements were systematically studied as a function of interisland spacing. The result was an increase of the switching field with reduction in spacing, with a maximum value for near zero spacing. However, in overlapped segments, all elements switched simultaneously at lower fields than the maximum at zero spacing, The switching field depends on the number of connected segments as described by the Jacobs-Bean model, whereas the switching of the separated islands is governed mainly by the field emanating from the nearest-neighbor magnetic poles. The reversal behavior of the branched contiguous array was also studied. The angle between the branch axis and the easy axis played a critical role in establishing the switching field. The reversal field of the branched segment reached a minimum at 45[degrees] and a maximum at 90[degrees]. A coherent rotation model, which includes the effect of the array geometry, appears to explain the trends. Index Terms--Angle, array, coherent rotation, interisland spacing, permalloy, switching field.

The topographic and magnetic structures of patterned 20-nm-thick Fe films grown on Si (001), polycrystalline NiO, and Si[O.sub.2] substrates are compared by scanning tunneling microscopy/magnetic force microscopy measurements under ultrahigh vacuum conditions to investigate the influence of the different substrates. Iron grows as a polycrystalline film. The size of the crystailites decreases from Si to NiO and Si[O.sub.2] substrates, respectively, while the surface roughness increases. The increased disorder in the film structure does not necessarily lead to an increased disorder in the magnetic domain structure. Instead, the magnetic structure of iron on NiO is the most complex, which can be attributed to the exchange coupling to the substrate. The antiferromagnetic NiO crystallites exhibit no long range crystallographic ordering which leads to random magnetic orientation. More evidence of the influence of the exchange coupling is found when comparing the magnetic structures of iron on NiO and Si[O.sub.2] as a function of film thickness in the range of 0-10 nm. Index Terms--Magnetic force microscopy, patterned films, scanning tunneling microscopy, ultrahigh vacuum, ultrathin iron films.

In this paper, an advanced extraction technique of the response function of giant-magnetoresistive (GMR) head for use in spin-stand imaging is presented. The essence of this technique is the spatial averaging of readback signals of many identically written 'point-like' charges resulted from dc-trimmed transitions. As a result of the averaging, the noise generated by random fluctuations of medium properties is filtered out. This extraction technique also restores the symmetry of the head response function by employing a nonstandard dc-trimming procedure and a modified bias condition for the read process. By using the extracted head response function, we were able to reconstruct magnetization images of overwritten data with a misregistration of 50 nm. Index Terms--Giant-magnetoresistive (GMR) heads, head response function, magnetic imaging, spin--stand.

Spin-stand imaging technique was used for spatial and vectorial characterization of thermal relaxation of recorded magnetization patterns. The highest decay rates was found to occur at the central region of the track close to the magnetic transitions while the magnetization at track edges increased resulting in track broadening.

Testing of a new method of magnetic imaging on a spin-stand is presented. It is concluded that the developed spin-stand imaging technique has at least the same degree of resolution and accuracy as the magnetic force microscopy imaging technique.

Research into the distribution of the transverse element of magnetization of recorded tracks is presented. It is suggested that the spin-stand imaging method can give both qualitative and quantitative data about magnetization distributions on recorded tracks.

Extensive experimental testing of the Preisach modeling of superconducting hysteresis is reported. This testing demonstrates the remarkable accuracy of the Preisach model in predicting various branches of superconducting hysteresis for various histories and in the wide range of temperatures.

A study was conducted to analyze scaling and data collapse in magnetic viscosity. Experiments were carried out for high-coercivity thin-film CoCrPt recording media using a vibrating sample magnetometer. Viscosity measurements were performed for the states that correlated with points on the descending branch of the major hysteresis loops. Experimental results indicated that viscosity coefficient curves observed for different temperatures collapse onto one universal curve.

Type III solar radio bursts have been commonly observed in the solar wind and coronal plasmas. Electron beams accelerated in the Sun's atmosphere generate weakly magnetized Langmuir (upper-hybrid) wave turbulence producing in turn electromagnetic emissions at the electron plasma frequency ωp and its harmonic 2ωp, via successive processes involving interactions between the background plasma, the waves and the beam particles. The impact of the random density fluctuations inherent to the background plasma on these processes requires the development of novel approaches and models. Owing to a new theoretical modeling, the radiation efficiency of electromagnetic waves radiated at ωp from a plasma source with random density fluctuations and developed upper-hybrid wave turbulence is calculated analytically and numerically. It is shown that the maximum radiation efficiency at frequency ωp scales as the average level of density fluctuations and as the ratio (c/vT)-2 (where vT is the thermal velocity). These scaling laws are found owing to two different and novel methods of determination of the electromagnetic radiation by turbulent inhomogeneous plasma sources through waves' transformations on randomly fluctuating density irregularities. These results contribute significantly to the understanding of the processes involved in the generation of Type III solar radio bursts. Their presentation is preceded by a summary of previous studies on the dynamics of beam-driven Langmuir turbulence in inhomogeneous solar plasmas. [ABSTRACT FROM AUTHOR]

The article explains the impact of plasmon resonances on the enhancement of the magneto-optic effects observed in the metallic nanoparticles.

Imaging capabilities of etched (100) and (210) oriented garnet films are analyzed and compared. The studies have shown that the etching of out-of-plane (100) garnet films have resulted in drastic reduction in saturation fields and an increase in contrast and resolution of images produced by the etched films is observed.

The air-core designs of Ethernet transformers in which the reduction of winding magnetic coupling is compensated by increasing the cross-winding capacitance coupling are described. The studies have shown that the capacitive cross-winding coupling has resulted in desirable characteristics of air-core transformers that are similar to those of ferrite core Ethernet transformers.

BiPrGdLu garnet films epitaxially grown on (210)-oriented substrates, which can be used as magneto-optical imagers, are studied. The garnet films have shown the phenomena of easy magnetization plane and the reduction of thickness of the garnet films through chemical etching has increased the clarity and spatial resolution of magneto-optical imaging.

An iterative algorithm for hysteresis compensation in micropositioning applications is described. The results of the testing of this iterative algorithm in tracking problems related to magnetic recording are presented.

The liquid phase epitaxy and characterization of single crystal (210)-oriented thin garnet films with Bi substitution is described. It is shown that the increase in the amount of Pr has increased the in-plane orthorhombic anisotropy field, while the rare-earth substitution by Bi has affected the canted orthorhombic anisotropy.

A magnetic-field sensor is proposed that uses thin garnet films with in-plane magnetization and strong magneto-optical activity. The advantages of this sensor are its high intrinsic sensitivity and the possibility of tailoring the field range for linear response.

Experiments on current-induced domain-wall motion (CIDWM) in the case of the domain walls (DW) trapped within the nanoscale constrictions in patterned NiFe structures are performed. The direction of CIDWM is found to be along the direction of the electron motion in absence of an applied magnetic field and in the direction of the field when in the presence of even relatively weak fields.

The study of the magneto-optical effects in garnets with in-plane magnetization under rotating magnetic fields is presented. The result shows that the optical response of the samples can be used to precisely determine the orientation of the crystallographic axes.

A dynamic track-following technique is developed that enables real-time reading of on-track data from off-centered hard disks on a spin stand. This technique makes use of piezoelectric transducers to dynamically control the radial displacement of the read head to follow off-centered tracks.

The spin-stand imaging technique is developed for the imaging and diagnostics of whole-track hard disk data from off-centered disks. It is shown that the hard disk tracks are nearly sinusoidally modulated in he radical direction due to eccentricity.

The impact of substrate rotation rate on the characteristics of liquid phase epitaxy grown Bi:LuGaFe garnets is presented. The growth rate is increased by a factor of 2, Faraday effect by 50 percent and index of refraction by 1.6 * 10(super -2) due to the increase in the substrate rotation rate.

Texture and grain-size effects on the exchange bias in sputtered polycrystalline NiO/NiFe bilayers are discussed. It is consistent with a model that the exchange interaction is caused by the reorientation of the moments with AF layer spins rotating.

High-speed massive imaging of hard disk data is developed by using the spin-stand imaging technique. The developed technique is a potent tool for analyzing hard disk drives including read head characterization.

The scaling technique for measured head response function in spin-stand imaging is described. This scaling technique has been tested and the appreciable improvement of reconstructed images have been demonstrated.

A novel approach to the calculation of plasmon resonance in metallic nanoparticle located nearby a dielectric object is presented. The plasmon resonance problem for such structure is formulated as a constrained eigenvalue problem for specific coupled boundary integral equations. By solving this eigenvalue problem, the resonance frequencies (wavelengths) of the metallic nanoparticle as well as the corresponding plasmon modes are computed. In this paper, two examples of application are considered and a good agreement between the computational results and analytical solution as well as with available experimental and numerical data is demonstrated. [ABSTRACT FROM AUTHOR]

Enhancement of the Faraday rotation of rare-earth iron garnet thin films offers the promise for development of compact and higher performance polarization dependent optical devices. Faraday rotation enhancement has been achieved utilizing strong localized electric fields induced by the excitation of plasmon resonances in gold nanoparticles deposited on garnet films. This paper presents experimental results that reveal strong Faraday rotation enhancement in bismuth-doped garnet films with gold nanoparticles of various dimensions and separations deposited on the epitaxial films. Stronger enhancements can be obtained by increasing the height and relative spacing between the nanoparticles formed on the garnet film surfaces. [ABSTRACT FROM AUTHOR]

Vector Preisach models of hysteresis are employed to describe vectorial hysteretic behavior of type II superconductors. The results of experimental testing of accuracy of the vector Preisach models are reported for the case of high-Tc Y[Ba.sub.2] [Cu.sub.3] [O.sub.x] superconducting samples. Index Terms--High-Tc superconductor, Preisach model, superconductor hysteresis, Type II superconductor.

This paper presents experimental evidence for scaling and data collapse of the magnetic viscosity (creep) coefficient for type II superconductors. It is demonstrated that, by using appropriate scaling, the creep coefficient versus magnetic field curves observed at different temperatures collapse onto one 'universal' curve. This data collapse suggests a peculiar self-similar structure of the creep coefficient as a function of two variables: magnetic field and temperature. Index Terms--Superconducting hysteresis, creep, type II superconductors, high-Tc superconductors.

When injecting an electron beam with a significant pitch-angle in a magnetoplasma, one has to take care that the parallel velocity of the electrons measured in the plasma does not only depend on the acceleration potential between the anode and the cathode of the electron gun, but also on the amplitude of the ambient magnetic field. The latter can play an important role when the actual acceleration distance of electrons in the gun vicinity, determined partly by collective processes that lead to potential modification in the gun environment, is large enough. Consequently, the actual beam pitch-angle can be noticeably different from the orientation of the electron gun. Index Terms--Electron gun, laboratory modeling of space phenomena, modulated beam injection in magnetoplasmas, resonant beam-wave interaction, whistler waves.