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The objective of this research is to calculate the minimum parameters required to make low-field low-size nano nuclear magnetic resonance (NanoNMR) a viable technology and potentially one of the future Lab-On-Chip technologies. By low field we signify an externally applied magnetic field of less than 0.5 T, and by low size we mean a magnet whose largest physical dimension does not exceed 25 mm. The goal is to develop small and cost-effective NMR spectrometers that can be used at room temperature in a small office environment. In this paper, tunneling magneto resistance (TMR) devices are used to sense the NMR signal. The parameters that are calculated are: minimum sample size and concentration required to obtain an adequate NMR signal, TMR sensor size, and its distance to the sample, RF coil size, RF frequency, and power. The nanoscale TMR sensors proposed in this paper were designed using an in-house developed software tool. The optimally calculated TMR sensors have [Fe.sub.50] [Co.sub.50] PL and FL layers, an area of 100 nm x 100 nm, a 0.3-nm-thick [Al.sub.2][O.sub.3] barrier and is biased at 200 mV. Index Terms--Nuclear magnetic resonance (NMR), giant magneto-resistance (GMR), tunneling magneto resistance (TMR), nano(NMR), lab-on-chip.

Today, conventional magnetic recording schemes are coming to an end because of the superparamagnetic limit. Heat-assisted magnetic recording (HAMR) may ultimately extend data densities beyond 1 TB/[in.sup.2]. HAMR systems utilize the phenomenon during which the magnetic properties of the recording media could be locally modified via heating (optionally, by an optical source in the near field) to temperature in the vicinity of the Curie value of the media material. As a result, heat induced by the optical source can temporarily reduce the magnetic coercivity of high anisotropy material to a level attainable by the magnetic writing head, thus making it feasible to record on relatively small ultra-high anisotropy (and thermally stable) grains, consequently enhancing the a real density dramatically. The key challenge is to develop a near-field transducer capable of delivering over 50 nW into a spot diameter of 30 nm. Traditional fiber schemes are barely capable of 0.1 nW. To resolve the issue, a laser diode could be placed with the emitting edge only a few nanometers away from the recording media. The light can propagate through a nanoaperture on the surface of an aluminum-coated emitting edge. This paper will present an experimental study of recording characteristics of various near-field transducers fabricated via focused ion beam (FIB). To count the number of photons emitted in the near field, a scanning near-field optical microscopy system has been implemented. The experiments indicate that the FIB-fabricated transducers could deliver power of over a few microwatt into a 30-nm spot (Fig. 7). Index Terms--Focused ion beam, heat-assisted magnetic recording (HAMR), scanning near-field optical microscopy.

The playback characteristics of common magnetoresistive heads applied in magnetic recording systems are examined based on bit-patterned medium. The results reveal that analytical solution for a pointlike reader is used to elucidate the playback resolution limits for given patterned medium morphology.

Playback characteristics of common magnetoresistive heads applied in magnetic recording systems are examined based on bit-patterned medium. Analytical solution for a pointlike reader is used to elucidate the playback resolution limits for given patterned medium morphology.

The selected aspects of the recording physics of magnetic data storage specific to writing and reading in patterned medium are discussed. The influence of a recording layer design on playback resolution is evaluated, which offers guidelines for the design and optimization of patterned magnetic recording medium.

The magnetization dynamics of soft underlayers (SULs) within perpendicular magnetic recording media were examined with the help of time-resolved Kerr imaging. The film switching speeds were found to be similar to the switching speed of the driving head for both longitudinal and perpendicular heads in the SUL films without media.

Cobalt ferrite Co[Fe.sub.2][O.sub.4] crystalline nanoparticles (50-100 nm) were produced by carbon combustion synthesis of oxides (CCSO). In this combustion synthesis process, the exothermic oxidation of carbon generates a thermal reaction wave that propagates through the solid reactants mixture of CoO and [Fe.sub.2][O.sub.3] converting it to cobalt ferrite. The extensive emission of C[O.sub.2] increased the porosity and friability of the product. The quenching front method combined with XRD and VSM characterization revealed that crystalline Co[Fe.sub.2][O.sub.4] particles formed in the early stage of the combustion, before the temperature reached its maximum. The maximum value of the coercivity of the quenched product within the front region was 940 Oe with a magnetization of 15 emu/g. The as-synthesized ferrites had hard magnetic properties with coercivity of 700 Oe and saturation magnetization of up to 47 emu/g. Index Terms--Carbon combustion, cobalt ferrites, nanostructured materials.

Selected aspects of the recording physics of data storage systems based on patterned magnetic recording medium are discussed. The micromagnetic study of the magnetization reversal in patterned magnetic recording medium is presented. The effects of bit size, head/medium misregistration, bit-to-bit spacing, soft underlayer (SUL) patterning, and side wall roughness on magnetization reversal are explored. The results offer the guidelines for the design and optimization of patterned magnetic recording medium. Index Terms--Bit magnetization reversal, micromagnetics, patterned medium recording.

Magnetoresistive playback off bit patterned magnetic recording media is studied. Three playback configurations are compared: not shielded sensors, shielded sensors commonly used in magnetic recording systems, and shielded differential sensors. Influence of patterned medium parameters including bit-filling ratio, bit shape, bit position jitter, bit-size variation on the playback signal is studied. Playback signal amplitude, D50, and signal-to-noise ratio are used to compare different playback sensor configurations. It is found that in general, shielded differential readers offer superior performance as compared to both shielded single sensor readers and not shielded readers. Index Terms--Bit patterned medium recording, differential playback heads, magnetic recording, magnetoresistive playback.

Using a Heisenberg model along with Monte Carlo, it is demonstrated that localized domain walls can be formed inside nanoconstrictions. The origin of the localized domain wall lies in the competition between atomic-scale exchange and the shape anisotropy. This leads to high sensitivity of the domain wall width on the shape of the nanoconstriction. Moreover, it is shown that ferromagnetic ordering is considerably reduced in these localized domain walls. Index Terms--Localized domain wall, nanoconstriction, scattering, spin disorder.

This work addresses the recording physics of narrow-gap single-pole heads (SPED in perpendicular recording. It is found that narrow-gap SPHs have reduced sensitivity with respect to nonzero skew angles. It is shown that while the efficiency of a narrow-gap SPH is generally reduced, even for the case of a gapless $PH, the efficiency differs from the efficiency of a 1-[micro]m-thick gap SPH only by a factor of two. The design parameter space for a narrow-gap SPH is investigated. Index Terms--Magnetic recording heads, perpendicular magnetic recording, single-pole magnetic recording heads.

This paper addresses the recording layer influence on the dynamics of soft underlayer (SUL) films. The static magnetic properties of soft magnetic films magnetostatically coupled to hard magnetic layers are correlated with their dynamic characteristics. The dynamic behavior is studied both theoretically and via direct experimental observation of the magnetization switching in a soft underlayer driven by a recording head. It is found that the dynamics of a SUL can be strongly influenced by magnetostatic coupling to a recording layer. Index Terms--Perpendicular magnetic recording media, scanning Kerr microscopy, soft underlayer (SUL) dynamics.

Application of reflection high-energy electron diffraction (RHEED) to texture determination is demonstrated for magnetic thin film applications. It is shown that both texture orientation and texture angular dispersion extracted from RHEED patterns are in agreement with the data obtained using x-ray diffraction.

Thin film perpendicular playback yoke-GMR heads capable of reading at a density of 100 Gbit/[in.sup.2] have been designed using 3D boundary element reciprocity modeling. Two basic head types are considered, a single pole and a ring-type geometry. The influence on the playback voltage and [D.sub.50] of the throat height, fly height, and permeability are studied. Isolated pulse response, roll-off curves, and off-track profiles are calculated. Media with and without a soft underlayer are also considered. The simulations show that of the designs studied the ring head in combination with the media without a soft underlayer has playback properties suitable for this density.

An ultrahigh anisotropy [L1.sub.0] phase is generated in order to perform magnetic force microscopy (MFM) imaging with the probe on magnetic tracks with linear densities ranging from 200 to 1200 KFCI. The results have shown sub-20-nm lateral resolution in ambient conditions and magnetic tracks and the focused ion beam (FIB)-fabricated FePt probe to be ideal for high-quality MFM study of next-generation recording media.

Micromagnetic modeling is used to study the physics of magnetic signal propagation in one-dimensional antiferromagentically coupled nanomagnetic arrays. The results have shown the possibility of successful signal propagation of magnetic cellular automata (MCA) at 2 GHz clocking field frequency with unlimited channel length.

The correlation between the magnetic properties and the microstructural and chemical composition modifications of Co/Pd magnetic multilayers upon annealing in ultrahigh vacuum is described. The studies have shown that the vacuum annealing under optimal conditions has improved the magnetic properties of Co/Pd multilayers for applications in ultrahigh density magnetic recording.

Magnetic force microscopy is used for studying the formation of stripe domains in Permalloy ([Ni.sub.80][Fe.sub.20]) thin films. The results have shown that the perpendicular anisotropy responsible for the formation of stripe domains have resulted from strain-caused magnetostriction and the thin-film microstructure shape effect.

A study was conducted to examine the physics of magnetization reversal in patterned high anisotropy [(Co/Pd).sub.n] magnetic multilayer arrays with varied magnetic island size, pitch, recording layer thickness, and the underlying multilayer magnetic properties. The findings suggested that ratio of switched magnetic islands to the total number of islands for a given reversing field depends strongly on the magnetic island geometry.

[(Co/Pd).sub.N] multilayers are deposited by magnetron sputtering and patterned into large periodic arrays in order to enable controlled domain wall injection for quantitative comparison of magnetic anisotropy energies. The studies have shown that the degree of d-shell hybridization at Co/Pd has interfaced directly that is correlated with the magnitude of magnetic anisotropy.

[He.sup.+]ion irradiation of continuous and patterned [(Co/Pd).sub.n] magnetic multilayer films is analyzed as a mean to control magnetic anisotropy and also evaluate possible ion irradiation damage involved in ion-beam proximity lithography patterning. The decrease in coercivity with increasing irradiation dose is more pronounced in samples with more bilayers.

The recording physics of playback in perpendicular recording systems are investigated. It is demonstrated that differential reader configurations possess advantageous playback characteristics in terms of higher playback amplitude, improved spatial resolution, and reduced sensitivity to fly height variation.

The physics of the playback process in perpendicular recording is explored. It is shown that due to the existence of effectively two layers of the magnetic charges in a perpendicular medium, the stray field sensed by a reader rolls off with the areal density essentially differently than it does in longitudinal recording.

The signal-to-noise ratio is extracted from the magnetic force microscopy images by using the autocorrelation method and is compared for determining the different aging conditions. It is found that the severity of the aging process is higher for low-density bit patterns due to the higher value of demagnetizing fields for large bits.

The magnetic force microscopy (MFM) was performed on two double-layered perpendicular media. Transition data was isolated from MFM images and analyzed for average noise along and across the track.

Using 3D modeling, guidelines for ultra-high density perpendicular recording were defined. The concepts developed to choose dimensions and materials were verified experimentally using MFM and spin-stand experiments with a 60 nm wide focused ion beam (FIB) trimmed head. Index Terms--Focused ion beam (FIB), magnetic recording with densities above 100 Gbit/[in.sup.2], perpendicular recording.

CoCrPtTa/Ti bilayer thin films have been sputter deposited onto both glass and Al substrates under high sputtering rate in a manufacturing environment. From microstructure and magnetic property studies, it is found that Cr segregation and stacking fault density are the two major issues in obtaining high quality perpendicular media. (0002) texture orientation spread and c lattice parameter remain almost constant within the variation range of the deposition parameters, though there is a small distinction between the media on glass and those on Al substrates. Index Terms--Co-alloy, magnetic properties, microstructure, perpendicular media, sputtering rate.