ERASE AND WRITE WIDTHS FOR NARROW TRACK HIGH DENSITY FLEXIBLE STORAGE MEDIA APPLICATIONS

Kevin D. McKinstry, Mark L. Watson, and Larry E. Daby Storage Technology Corporation, Louisville, Colorado 80027-81 10, USA

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With the continued pressure on both the cost and capacity of archival storage requirements, current flexible media roadmaps now anticipate cartridge capacities in excess of 1 TB in the very near future. The increase in cartridge capacity can be achieved by increasing the linear data density and also the number of tracks written across the width of the tape. The planned increase in track density will require the recording head to write, and read, significantly narrower track widths than used in current flexible media products. Thus, as the track widths are decreased the width of the erase bands will become an increasing proportion of the overall effective written track width. It is therefore essential that both the erase band and effective write widths are fully characterized.

Although the effective width of the erase band critically depends on media magnetic and physical characteristics, it also depends on the write pole dimensional control. This places very significant demands on the head fabrication technologies at the wafer fabrication and head assembly capabilities. To overcome this, and to provide well-defined track width control, a novel ‘Inverted write head structure has been developed. In this design the narrow pole tip is patterned in the lower write pole to define the width of the trailing pole. As the lower pole has significantly less topography than the ‘top”pole, it has been found that the pole itself can be very accurately patterned, using a combined ion milling I etch process. Thus the combination of the improved field gradient and pole definition process enables very accurate track width control.

We report here the results of extensive investigations of the influence of the write head design and operating point on both the effective write width and erase band width. The effective erase band widths in both directions were found to be very strong functions of the write current for the media used in these tests, while the write width depended both on which pole the track was written with and write current. The relative dimension of the inverted pole also played an important role in determining the write width.

NARROW POLE WIDE POLE

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pTRACK PROFILES FOR INVESTIGATING SIDE EFFECTS OF ADVANCED SILICON HEADS FOR HELICAL SCAN TAPE SYSTEMS

A. Hozoi”, J. P. J. Groenland”, J.C. Lodder”, J.B. Albertinib ‘Systems & Materials f o r Information storage (SMI), MESA’ Research Institute,

University of Twente, P.O. Box 21 7, 7500 AE Enschede, The Netherlands bAlditech, CEA-LETI, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France

Track and ptrack scans are common techniques applied in hard disk systems for investigating side writing and side reading, but also for characterizing the response of MR read heads. These methods are less implemented in tape systems, where the contact recording mode and the flexible medium make it difficult to obtain a smooth relative movement between head and medium. Positioning instability generates fluctuations in track profiles [I]. We optimized an experimental system, using helical scan type heads and tape wound on a rotary drum, for measuring submicron track profiles. Writing and reading operations are performed with the same helical scan silicon (HSS) head, fabricated with advanced thin film technology. HSS heads feature unique properties such as an integrated solenoid coil (DC resistance < 8 Q, for 40 turns), and very small pole widths. The very good alignment of the polar pieces is expected to minimize side effects. In this paper, we report about ptrack profile measurements applied for investigating track edge behavior of HSS heads in combination with MP and ME tapes. Heads with optical pole widths as narrow as 3.3 pm, and 0.1 1 pm gap length have been studied. Narrower tracks are obtained by recording a first track and partially erasing it from one side by writing a second track at a different wavelength (Fig. 1). The accuracy of the positioning achieved in our system, better than 0.1 pm with all precautions, allows using this method for side erasure measurements. Using a 0.5 Fm wavelength track to partially overwrite a 0.4 pm wavelength we find a side erasure band of 0.3 pm (with MP tape, H, = 135 W m ) . Results can be compared with MFM observations-and qualitative agreement is proved. We also describe novel profiling methods for quantifying side reading, and report experimental results. The difference between the side erasure band (SEB) and the side reading band (SRB) can be determined by writing a track in the middle of two adjacent tracks having different wavelengths (Fig. 2). All wavelengths are read during the same scan.

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Cfoss-track position (pm) Cross-track position (pm)

Fig. 1. Side erasure measured by profiling Fig. 2. Novel profiling method for two overlapped tracks and their MFM image.

[ l ] S. Fukuda et al., IEEE Trans. M a p . 36, 2499-2501, (2000).

measuring edge effects.

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