Mohamad Towfik Krounbi

Beyond discrete tracks : other aspects of patterned media

The surface of a thin‐film disk can be patterned using standard lithographic techniques to form discrete tracks as narrow as 0.5 μm. These studies have been extended to patterns formed when an etched track is broken into discrete segments by etching away some portions of a discrete track. Abrupt changes in the magnetization can be obtained by dc erasing the medium, giving readback signals with ∼50% of the amplitude of conventional transitions when the gap of the readback head is aligned with the edge of the media pattern. The implications of these results for servo and read‐only applications are discussed.

Recording characteristics of submicron discrete magnetic tracks

Discrete magnetic tracks with widths as narrow as 0.5 μm have been formed by etching the surface of Co-alloy film disks. Transitions can be written and read back from widely spaced discrete tracks using conventional heads. A linear variation of pulse area with track width is observed for isolated pulses. Noise measurements for tracks that are either dc erased or written with transition densities up to 3000 flux reversals/mm show a linear variation of media noise with (track width)1/2, in agreement with the behavior expected for media noise uncorrelated across the width of the track.

The study of recessed MR sensors with un-laminated and multi-laminated flux-guides

The authors have fabricated unshielded and shielded magnetoresistive (MR) sensors with various flux-guide configurations and studied their behavior using MR response and Kerr effect techniques. Results show interesting effects involving interactions of the MR sensor with the flux-guides and with the shielding environment, ranging from transverse bias enhancement effects of shields and flux-guides to the excitation of multidomain states in unshielded MR sensors by strong signal flux from the long back flux-guides. The multilaminated flux-guides are shown to be much better in noise behavior compared to the unlaminated flux-guides, although small amounts of jumps are still present, as expected from edge-curling wall magnetics. The presence of a long back flux-guide enhances the read sensitivity distinctly, but might also render flux-guide noise problems more critical in the operation of the sensor. >

Reduction of edge noise in thin film metal media using discrete tracks

Discrete tracks were used to determine the importance of edge effects in the recording performance of thin-film metal media. A small reduction of signal amplitude is observed when the discrete track width exceeds the head width, and the edges of a conventional track contribute noise but no signal to the readback process. Direct measurements of the error rate as a function of distance off-track show very similar values for discrete and conventional tracks of comparable width. This indicates that edge effects are not a significant source of errors for this particular head/disk combination. >

Inductive write heads using high moment pole materials for ultrahigh areal density demonstrations

In this paper, the high moment materials and their applications in the write heads for these areal density demonstrations will be discussed. Due to high intrinsic magnetic anisotropy and magnetostriction, which is typically about 4.5x10/sup 5/, FeCoN films exhibit typical coercivity in excess of 50 Oe, and isotropic in-plane magnetic properties, under un-optimised process conditions. A typical hysteresis loop of the film is shown.

A design concept of array heads

This paper describes a novel design concept and experimental hardware data of array heads for close-packed track recording. The heads are batch fabricated on wafers in a linear fashion. These 60-turn thin-film inductive heads are designed with 6 /spl mu/m pitch helical coils and planar side-by-side P1/G/P2 yokes structure. The linear head array is placed along the upstream-to-downstream direction of the track. By skewing the array slightly off the track direction, each head of the array aligns to an individual track. In this case, the track pitch is about 5 /spl mu/m, which is the yoke height. With this head arrangement, even though a thermal expansion causes the head-to-head distance to increase along the upstream-downstream direction, it does not cause a thermal induced track misregistration problem. The increased head-to-head distance only affects the timing of signals between tracks, which can be compensated by the channel electronics. Thus, the thermal induced track misregistration problem is eliminated using this design. The guard bands between tracks are not necessary, and a close-packed track recording is possible. A state of the art head impedance of the 60-turn head is obtained: 11 /spl Omega/ and 0.40 /spl mu/H. The gap-to-gap pitch is 100 /spl mu/m. The overall head-to-head isolation is greater than 50 dB at 10 MHz. Such a large isolation is realized by suppressing the capacitive coupling between lead wires using a ground plane and grounded wall structures. The tight winding of the helical coils reduces the magnetic coupling between the heads.

Thin film head with staggered pole tips

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. >

Batch-processed close-track array heads (abstract)

This article describes novel array heads for close packed track recording. The heads are batch fabricated on wafers in a linear fashion (Fig. 1). These 60-turn thin-film inductive heads are designed with 6 μm pitch helical coils and planar side-by-side P1/G/P2 yoke structures. The linear head array is placed along the upstream-to-downstream direction of the track. By skewing the array slightly off the track direction, each head of the array aligns to an individual track (Fig. 2). In this case, the track pitch is about 5 μm, which is the yoke height. With this head arrangement, even though thermal expansion causes the head-to-head distance to increase along the upstream–downstream direction, it does not cause a thermally induced track misregistration problem. The increased head-to-head distance only affects the timing of signals between tracks, which can be compensated by the channel electronics. Thus, the thermally induced track misregistration problem is eliminated using this design. The guardbands betwe...