薄膜ヘッドのオフトラック特性とトラック端部の媒体磁化分布の観察

Until now, the return-path core of single-pole thin film heads for perpendicular magnetic recording have been located at a finite distance from the main pole in the head scanning direc- tion. In this type of head, distortion of the reproduced waveform is introduced by the extra pulse appearing when the return path core comes into direct contact with the medium. In order to eliminate this distortion, we developed a single-pole thin film head with a new shape, called a FiTR head (single-pole thin Film head with Transverse Return flux path core), with the return-path core set at a definite distance to one side in the track width direction. The recording field distribution and reproduction characteristics of the head were investigated in simulations and experiments. The new thin film head has high sensitivity and an excellent recording field distribution. The reproduced waveform of the head is free of distortion.

A linear, statistical model is described which predicts the power spectrum of measured noise in bulk-demagnetized (i.e. AC-erased) thin-film magnetic recording media. It is shown that the noise is the result of magnetic flux which is ascribed to erasure-induced transitions along the track length in the medium. The noise power spectrum for a rigid disk medium is shown to correspond to the power spectrum of Poisson-distributed induced transitions along the track length, while noise along the track width is sufficiently described in terms of a uniform, average magnetization with small variance. Experimental data from two thin-film disks are used with the model to estimate the Poisson parameter for each disk. It is demonstrated that AC-erased noise from particulate media can be considered as a limiting case of the Poisson model. >

In this work, we present an analytical study of temperature rise due to Joule heating in magnetoresistive heads. Using a transmission-line type model and proper boundary conditions, we derived an analytical formula, including thermal resistance, finite track width and conducting lead effects. Results show the temperature rise due to Joule heat is non-uniform along the MR track width direction: the temperature rise has its peak at the center and decreases rapidly off the track. The averaged temperature rise, which is what one measures experimentally, is 20% lower than the maximum temperature rise at 2 /spl mu/m track width. Although the temperature distribution also depends on thermal conductivities of both MR and lead materials, it more strongly depends on the thickness and thermal conductivity of the gap dielectric material.

A novel scheme essentially eliminates side-reading while maintaining on-track magnetic sensitivity for spin-valve read heads. By directly patterning a magnetic layer that is antiparallelly coupled with the free layer beyond the track edges, the magnetic torque generated by signal field in the wing regions of the free layer can be counterbalanced by the torque generated by the patterned layer via the antiparallel coupling. The magnetic read width of the sensor becomes essentially the same as the physical track width for track widths as low as 50 nm. With this scheme, the on-track magnetic sensitivity exhibits virtually no reduction as track width reduces from 200 to 50 nm. In addition, the scheme enables recessing the contact leads from the track edges to reduce shield-to-shield widening at the track edges.

This paper describes a design for a near field hybrid recording system that uses a mode index waveguide lens in place of a SIL or optical fiber. The mode index waveguide lens is fabricated on the back of an air bearing slider with a thin film magnetic head and giant magneto resistance (GMR) sensor for reading and writing. The optical spot from the waveguide heats the media to its Curie temperature such that within the spot a region with a reduced coercive field (`Curie cylinder') is created. The thin film head then applies a magnetic field to switch the magnetization within the Curie cylinder thereby recording a written mark. In the system proposed here, the track width of the optical spot is less than that of the thin film head and as such defines the recording track width. A GMR sensor is used to sense the flux leakage from the surface of the media and may also be laser assisted. Calculations predict an aerial density of 70 Gbits/inch<SUP>2</SUP> when using a simple mode index lens fabricated from a SiO<SUB>2</SUB>/SiN<SUB>x</SUB>/SiO<SUB>2</SUB> waveguide. Furthermore, by using advanced lens designs and innovative materials, the track width can be reduced further thereby offering a promising way to achieve 500 Gb/inch<SUP>2</SUP>.

The feasibility of high track density recording in a perpendicular magnetic recording system has been investigated. The properties of the magnetic field of a single pole type (SPT) head having a narrow track width were studied by using a large scale model of a head and a medium. The y-field gradient of the SPT head near the track edge is steeper than the x-field gradient of a ring head, and it was confirmed by Bitter technique that the recorded track width acculately coincides with the width of the main pole of the SPT head. Perpendicular recording using the SPT head also has superior off-track characteristics and the crosstalk signal is hardly detected even at very narrow track pitches. From a magnetics point of view, no problems exist in narrowing the track width of the SPT head in perpendicular recording. Narrow track recording and reproducing with SPT head of only 6.5 μm in track width could be achieved with sufficient signal to noise ratio in perpendicular flexible disk systems.

The authors propose a cost-effective approach to reduce write track widths down to the sub-micron range. Thin-film heads with staggered pole tips, such that the track width is defined by the overlap of pole tips, have been fabricated with processes similar to the conventional thin-film head process. Both the transverse and the longitudinal configurations have been examined. Heads of both configurations have worked well, achieving satisfactory overwrite performance and track definition. Narrow track write heads capable of writing transitions as narrow as 0.7 mu m have been demonstrated. such sub-micron write heads hold potential for achieving high track densities in conjunction with magnetoresistive read heads. >

Narrow track recording in a double-layer perpendicular film medium is studied via micromagnetic modeling. A 3-D probe head field with a track width W=1.5 mu m is used for recording simulations. Recordings of multiple consecutive transitions are simulated. Edge transition patterns and edge overwrite properties are characterized. Simulated transition magnetization pattern at track edges turns towards to the head motion direction and extends to the next transition front. Edge overwrite is studied by simulating recording of a new track over a previously recorded track. It is found that the edges of the new track exhibit no separations with the overwritten track and the intertrack edge of newly recorded transitions is strongly modified by the previously written transitions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sputter deposition is a facile and widely used technique for fabricating thin-film materials. Electrochemical dealloying, on the other hand, is a promising method for creating nanoporosity, and therefore increasing surface area, in metallic materials. Surprisingly, little work has been done on the application of electrochemical dealloying to sputter-deposited thin films. Here, we prepare FexCu1–x thin films by sputter deposition to be then electrochemically treated to create porosity. We investigate the structural and magnetic properties of as-sputtered and electrochemically treated films. We find that the morphology, crystal structure, and magnetic properties are highly dependent on initial film composition. For high copper content films (Fe29Cu71), relative Cu content is found to decrease during the dealloying process. For these films, the crystal structure is not greatly affected by the induced porosity and the porous films show increased saturation magnetization. However, for the more Fe-rich compositions (Fe63Cu37), we find that Fe is preferentially lost and making the films nanoporous induces a crystal structure change from body-centered cubic (bcc) to a mixture of face-centered cubic (fcc) and bccphases. These same porous films show a decrease in saturation magnetization and a large increase in coercivity compared to the as-sputtered films. These films are attractive as high-surface-area magnetic components because of the tunability of their magnetic properties and their high surface area due to porosity. To the best of our knowledge, these results constitute the first example of nanoporous, magnetic thin films by prepared by sputtering and subsequent electrochemical treatment.

For long durability of magnetic media and head sliders, protective overcoats of hydrogenated amorphous carbon (a-C:H) are generally used. In this study, microtribological studies of hydrogenated amorphous carbon coatings deposited on a single-crystal silicon using three different deposition techniques—sputtering, ion beam and cathodic arc—were studied using atomic force/friction force microscopy (AFM/FFM). Roughnesses of all coatings at two scan sizes of 1 μm × 1 μm and 10 μm × 10 μm are comparable. Surface topography of sputtered carbon coating shows some particulates on the surface. Cathodic arc carbon coating exhibits the lowest coefficient of friction value followed by ion beam and sputtered carbon coatings. Microscratch and wear resistance and nanohardness of cathodic arc carbon coating are superior to those of ion beam and sputtered carbon coatings. Cathodic arc deposited carbon coatings are potential candidates for magnetic disks and heads.

Environmental magnetism methods were applied to surface lake sediments from seven basins located in a climosequence within the Transmexican Volcanic Belt and the Los Tuxtlas Volcanic Field in Central Mexico. The main aims are: 1) to determine the characteristics of magnetic mineralogy, 2) Evaluate the influence of climatic conditions and the geological age of source rocks on these characteristics. 3) Explore the relationship between magnetic mineral properties, climate and catchment age. 4) Integrate existing data from soil and paleosol profiles to provide a broader understanding of environmental and climatic controls on magnetic mineralogy. Results were compared to previous soil environmental magnetism analyses. Five end-members of magnetic components are recognized: 1) detrital partially oxidized Ti-magnetite, 2) pedogenic detrital magnetite, 3) authigenic magnetite formed from both biotic and abiotic processes, 4) detrital and 5) pedogenic hematite. The concentration of magnetic minerals and the distribution of grain sizes are closely linked to climatic regimes and hydrological dynamics. Lakes located in humid regions exhibit the highest concentration of magnetic mineral values, reflecting enhanced detrital input driven by rainfall-induced sediment flux. The observed differences between the magnetic parameters of soils and lacustrine sediments suggest that additional authigenic processes take place within the lakes, expanding the range of magnetic grain sizes and coercivities. This effect is particularly pronounced in warm and humid climates, where maghemitization and the mixing of detrital and authigenic components are more complex. Older basins (>1 Ma) are enriched in fine-grained (SD and SP) pedogenic magnetite and hematite, indicating a substantial soil-derived contribution . Métodos de magnetismo ambiental fueron aplicados a sedimentos superficiales de lagos de siete cuencas ubicadas en una clímosecuencia dentro de la Faja Volcánica Transmexicana y el Campo Volcánico de Los Tuxtlas en el centro de México. Los objetivos principales son: 1) determinar las características de la mineralogía magnética, 2) evaluar la influencia de las condiciones climáticas y la edad geológica de las rocas fuente en estas características. 3) explorar la relación entre las propiedades minerales magnéticas, el clima y la edad de la cuenca. 4) integrar datos existentes de perfiles de suelos y paleosuelos para proporcionar una comprensión más amplia de los controles ambientales y climáticos en la mineralogía magnética. Los resultados se compararon con análisis previos de magnetismo ambiental de suelos. Se reconocen cinco miembros finales de los componentes magnéticos: 1)Ti- magnetita detrítica parcialmente oxidada, 2) magnetita detrítica pedogénica, 3) magnetita autigénica formada a partir de procesos bióticos y abióticos, 4) hematita detrítica y 5) pedogénica. La concentración de minerales magnéticos y la distribución de los tamaños de grano están estrechamente vinculadas a los regímenes climáticos y la dinámica hidrológica. Los lagos ubicados en regiones húmedas exhiben la mayor concentración de valores minerales magnéticos, lo que refleja un mayor aporte detrítico impulsado por el flujo de sedimentos inducido por la lluvia. Las diferencias observadas entre los parámetros magnéticos de los suelos y los sedimentos lacustres sugieren que dentro de los lagos tienen lugar procesos autigénicos adicionales, lo que amplía el rango de tamaños de grano magnético y coercitividades. Este efecto es particularmente pronunciado en climas cálidos y húmedos, donde la maghemitización y la mezcla de componentes detríticos y autigénicos son más complejas. Las cuencas más antiguas (>1 Ma) están enriquecidas en magnetita y hematita pedógena de grano fino (SD y SP), lo que indica una contribución sustancial derivada del suelo. • Increase in coercivity suggests greater degree of maghemitization in warmer climates • High DP in coercivity suggests the presence of soft biogenic magnetite in samples • Higher concentration of SP and SD suggest more extensive pedogenesis

For the MR strips stabilized by the permanent magnet films, we numerically analyze the effects of the leakage field of the permanent magnet films on the bias angle in the MR films. Using the magnet films as the domain control films, magnetization rotation in the MR films at the track edges is suppressed by their leakage fields and will in turn decrease the effective track width. The decrease effective track width is thought to be due to the large leakage field especially at the track edges, so we examined some cases of decreasing the leakage field at track edges. Among the cases, the effective track width was most effectively enlarged when the distance between the magnet films was widened compared with the spacing of the leads. >

In order to improve off-track capability and thus to achieve higher track density, both sides of the upper and lower pole tips of inductive thin film heads were trimmed to become nearly the same in width, through photolithography and ion milling processes at the air bearing surface. The off-track capability improvement attained by the pole trimming was experimentally estimated by performing off-track profile evaluation and measurement. The difference between the effective track width and the upper pole width, which represents the amount of track side writing and side crosstalk effect, was found to be reduced to 68% of that seen in conventional thin film heads. It was also found that the track interval can be squeezed by as much as 1.0 /spl mu/m more than conventional thin film heads, based on the 747 curve comparison. >

Co-Pt cylindrical micromagnets with 2-/spl mu/m diameter have been successfully fabricated by electroplating through resist masks onto Cu[111] seed layers. The influence of the applied current density and cylinder height on the magnetic properties have been investigated. Both coercivity and retentivity increase with increasing aspect ratio, due to the combined effect of the decreasing demagnetizing field and the increasing perpendicular crystalline anisotropy of Co-Pt, which grows preferentially with HCP(0001) orientation. Values as high as 4.3 kOe for the coercivity and 6.9 kG for retentivity have been observed. Large energy products up to 5.38 MGOe (42.83 kJ/m/sup 3/) were attained, rendering these structures potential candidates for hard magnetic components in microelectromechanical systems.

Multitrack yoke-type MR readout heads having a single shared front fluxguide with a highly anisotropic permeability, have been designed and evaluated. The well defined microtrack response profiles of these heads show that the anisotropy of the permeability confines the flux-detection to the area on tape in between the contact leads of the MR element. This can be exploited in "full-density" tape recording heads which read directly a number of adjacent tracks.