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Research is presented concerning the use of grazing incidence x-ray reflectometry to investigate the usage of surface oxidation as a diffusion barrier. The deposition of Al on ferromagnetic metals is discussed.

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 topographic and electronic structure of 10-20-nm-thick permalloy films has been investigated under ultrahigh vacuum conditions. The films were characterized using scanning tunneling microscopy/spectroscopy. Permalloy grows as a polycrystalline film. The size of the crystallites is in the range of 5-20 nm for the permalloy films. The spectroscopic data show a distinct minority electron state, which can be assigned to the presence of iron in the permalloy surface. It was found that the state not only decays but also shifts in position when moving the STM tip away from the center position of the iron atoms. Index Terms--Chemical identification, permalloy, scanning tunneling microscopy, scanning tunneling spectroscopy.

In this work, we study the elastoresistance of CoFe/Cu antiferromagnetically coupled giant magnetoresistive films. This refers to variations in resistivity due to strain-induced changes in magnetization. This type of phenomenon, observed on a multilayer, originates mainly from the inverse magnetostriction effect, taking place within the magnetic layers. Since these magnetizations are coupled, strain induces an overall effect on the film resistivity. Our measurements reveal that these effects lead to enhanced strain sensitivity in comparison to films made of the materials the materials that compose the multilayer. Index Terms--Giant magnetoresistance, magnetoelasticity, strain measurement.

The effectiveness of Al, Au, Cu, Ni, Fe, and Ta films with thicknesses up to 4 nm for protecting a Co surface from oxidation in air at room temperature is investigated. It was seen that the best choices for protecting Co from oxidation were Al and Ta and Au was not very effective for protecting Co.

Both ferromagnetic (FM) and charge-ordered domain structures of [([La.sub.1-x][Pr.sub.x]).sub.0.67][Ca.sub.0.33]Mn[O.sub.3] thin film were detected by magnetic force microscopy (MFM) and electric force microscopy (EFM) operated at low temperatures near the peak resistance temperature ([T.sub.p]). The in-plane-like FM domains of submicrometer size emerge below [T.sub.p], and their magnetic interaction with an MFM tip becomes stronger as the temperature is reduced. Charge-ordered insulating regions have the strong electrostatic interaction with an EFM tip near [T.sub.p], and the interaction correlates well with the temperature dependence of resistivity of the film. Index Terms--Charge ordering, colossal magnetoresistance, EFM, low temperature, magnetic domain, MFM.

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.

The correlation of the topographic and magnetic structure of as grown ultrathin iron films on a polycrystalline NiO substrate under ultrahigh vacuum (UHV) conditions is examined. The interaction between the iron crystallites increases with growing film thickness resulting in larger domains with average size of 200 nm up to a film thickness of 15 nm.

It has been possible to convert a commercial magnetic force microscope to operate at low temperatures. The efficiency of the technique to investigate paramagnetic to ferromagnetic transition in colossal magnetoresistive materials has been demonstrated.

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.

The static and dynamic magnetic properties of structures are investigated by complementary techniques such as magneto-optic Kerr effect (MOKE), magnetic force microscopy (MFM) and Brillouin light scattering (BLS). Electron-beams lithography is exploited to prepare arrays of identical, micron-sized square-shaped dots with precise control over the particle shape, orientation, and spacing.

The conditions that lead to specific domain configurations and the associated switching characteristics of small permalloy islands were studied by using magnetic force microscopy. The studies involving, in situ applied field similarly revealed the mechanisms of the reversal processes for each of the configurations, which correlated quite well with the values of the switching fields.

A study was conducted to analyze the magnetization distributions of an array of small NiFe elements. Lorentz transmission electron microscopy and magnetic force microscopy were utilized to carry out the analysis. The samples were made using electron beam lithography and lift-off patterning on electron transparent Si3Ni4 membrane substrates. Experimental results indicated different facets of the magnetization distributions on soft magnetic thin films.

A study was conducted to analyze the magnetization reversal process in an array micron sized NiFe patters using magnetic force microscopy during the presence of external fields. The behavior of the magnetization distribution correlated with the aspect ratio and the direction of the applied fields. In addition, magnetic behavior was characterized as an external field applied along the hard axis.

The Magnetic Force Microscopy (MFM) image reconstruction technique has overcome difficulties in interpreting MFM images of data tracks written on longitudinal recording media. In this work, MFM image reconstruction is used to study the vector magnetization components of closely spaced tracks. Untrimmed and Focused-Ion Beam (FIB) milled, trimmed thin-film inductive heads of widths 4.5[[micro]meter] and 2.5[[micro]meter] are used to write tracks with wavelengths ranging from 0.75[[micro]meter] to 3[[micro]meter]. In order to analyze the limitations of high density recording, the magnetization at the edges of neighboring tracks is considered. It is shown that the width of the cross-track component of magnetization is strongly dependent on the relative phase difference of adjacent tracks, the track width, and the linear recording density.

The role of stress on magnetic properties of epitaxial ([La.sub.0.7][Sr.sub.0.3])Mn[O.sub.3] (LSMO) films has been studied. We have investigated 1100 [Angstrom] thick LSMO films deposited on LaAl[O.sub.3] (Sample L, under a compressive stress) and SrTi[O.sub.3] (Sample S, under a tensile stress) using the magnetic force microscopy (MFM), DC hysteresis loop, ferromagnetic resonance (FMR) measurements. The magnetic force microscope image of Sample L shows a 'maze-like' pattern indicating a sizable out-of-plane magnetization, while the magnetic image of Sample S shows a 'feather-like' pattern indicative of an in-plane magnetization. The hysteresis loop and ferromagnetic resonance measurements give quantitative evidence for the role of the lattice mismatch between the film and the substrate in the magnetic anisotropy of the two films. Our systematic examination of various thickness LSMO films on LaAl[O.sub.3] reveals that the maze pattern is exhibited only between 500 [Angstrom] and 1700 [Angstrom] thick films. Despite of larger anisotropy, no maze pattern is observed in films thinner than 360 [Angstrom].

Patterns of submicron cobalt islands were created on silicon by using self-assembled co-polymers as etching masks. The synthesis conditions were varied to create specific magnetic island morphologies. The magnetic structure and magnetization reversal of interconnected, as well as interacting and non-interacting islands were systematically studied using magnetic force microscopy. Differences in magnetic characteristics were observed and correlated with the thin film morphologies. The result of these studies include the transition from single to multidomain configuration as a function of island size, domain boundary characteristics near coercivity, evidence of magnetization rotation with increasing reverse magnetic field, and evidence of collective switching behavior in interacting single domain islands.

A novel experimental technique of magnetic biasing for the Magnetic Force Microscopy (MFM) imaging is introduced. This technique enforces linearity of the imaging system and, in this way, it facilitates the interpretation of images of magnetization patterns. The technique of numerical reconstruction of the curl-free vector magnetization from a raw image obtained by the linearized MFM system is presented. An example is given which demonstrates the significant difference between the reconstructed magnetization and the raw image. This stresses the usefulness of magnetic biasing and image reconstruction for MFM image interpretation.

Two component-selective in vector functions Hx and Hy directly monitor the arrangement of recorded patterns in magnetic systems. In-plane Hx images identify lateral side written forms and Hy images identify dark and bright spots on the track edge. Two transversely oriented magnetic dipole fringing fields are detected as functions of the recording wavelength.

The magnetic force scanning tunneling microscope was used to obtain images of three distinct cartesian components of the vector magnetic field produced by a magnetized surface. The various combinations of orthogonal magnetic-field components were two-dimensionally mapped. Unusual recorded magnetization pattern characteristics were observed.

Fourier series transformations and uniform magnetization properties are used to directly calculate magnetic fields generated from recorded surfaces containing multiple tracks. Calculated longitudinal and vertical recording solutions are used to compute transition lengths, track separation and head registrations as functions of the output voltage.

A newly developed vector Preisach-type model of hysteresis is applied to the computation of static magnetic fields in media with hysteresis. Time stepping technique is used to trace the time evolution of local magnetic fields which form the history of magnetizing process. At each time step, the magnetostatic problem is formulated in terms of an integral equation and an efficient iterative algorithm is employed for solving this problem. The technique has been used to simulate some magnetic recording processes. Sample results of these simulations are given in the paper.

The characteristics of magnetization patterns on rigid thin film disk media with wavelengths ranging from 20 to 1 micrometer were investigated using magnetic force scanning tunneling microscopy. The results showed that there were two major effects to which signal loss was attributable: magnetization reduction and the formation of bit clusters in the material. The tracks gradually lost their ability to retain the recorded pattern as the wavelength decreased.

The magnetic field distributions of overwritten patterns on rigid thin film disks were investigated using magnetic force scanning tunneling microscopy. The results showed that at high densities and offsets smaller than 2 micrometers, track width modulation was induced along the edges by overwritten transitions. These effects were less conspicuous at low densities.

A new technique for the imaging of magnetization patterns is presented. The method is based on magnetic force scanning tunneling microscopy and the measurements were analyzed using a point charge model. The results showed that the point charge model was an accurate tool for the calculation of the probe impulse response.

A point charge model was used for magnetization image reconstruction of data obtained by a magnetic force scanning tunneling microscope. The results showed that the technique is effective for processing and reconstructing magnetic force scanning tunneling microscopy images. The reconstructed image was very different from the recorded magnetization pattern although it accurately reflected its nature.

We have made a theoretical analysis of the interaction between a flexible triangular probe and a typical magnetic pattern on a recorded surface. The use of this analysis allows the measurement of the magnetic fields of the recorded patterns imaged by a tunneling magnetic force microscope.

The magnetic force scanning tunneling microscopy is briefly discussed and demonstrated to successfully image overwritten data on commercial rigid magnetic disks. In particular, clear images of unerased remnants of the previously stored data are presented. These unerased data are attributed to slight radial deviations in write head tracking due to the intrinsic limitations in the electromechanical positioning of the head.

Scanning tunneling spectroscopy and microscopy is used for correlating the local density of electronic states with the topography of Fe on MgO and MgO on Fe. The studies have shown that at one monolayer, the measured density of states is different from either very thick or very thin MgO, suggesting the possibility of an interfacial layer that are distinct from the Fe (100) and MgO (100) surfaces.

The magnetization reversal process and the spectrum of magnetic excitations of NiFe/Cu/NiFe circular nanorings are examined by magneto-optic Kerr effect, magnetic force microscopy and Brillouin light scattering (BLS). The presence of dipolar coupling between the layers has caused the appearance of either in-phase (IP) (acoustic) or out-of-phase (OP) (optical) modes, resulting in an eigenmode spectrum.

Ultrahigh vacuum (UHV) high resolution scanning probe microscopy is used to investigate the growth and magnetic properties of epitaxial Fe films on MgO(001) at different substrate deposition temperatures. The magnetic properties are dependent on the film thickness, whereas magnetic structures have changed from complex patterns to well ordered magnetic ripples and domain walls at higher coverage.

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 domain wall resistance in Ni80Fe20 nanowires containing narrow constrictions down to 15nm in width is discussed. The overall anisotropic magnetoresistance of the structure dominates wider constrictions and constrictions narrower than ~40 nm display an additional contribution from a domain wall.

The results of half-metallic ferromagnets formed by atomic nanocontact of CrO2-CrO2 and CrO2-Ni that show as much as 400% magnetoconductance are presented. The conductance is proportional to the area of the nanocontact times the transmittivity of the nanocontact and the transmittivity of the nanocontact is approximately inversely proportional to the bulk resistivity of the material.

Provides information on a technique for calibrating the force gradients and probe magnetic moment in phase-contrast magnetic force microscopy (MFM). Advantages of MFM in understanding surface magnetism; Method used to get an effective magnetic moment of the probe; Workability of this calibration method.