Ampex Corp: Digital Storage Message Board

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Technology Stocks : Ampex Corp: Digital Storage

AMPX 8.540

-2.0%

Dec 24 12:59 PM EST

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To: Wayne Umfleet who wrote (2602)	4/16/1997 4:18:00 PM
From: Gus	of 3256

KM was the subject of a seminar, part of a weekly series, conducted yesterday at the Center for Magnetic Recording Research (CMRR) at the University of California, San Diego. "Keepered Longitudinal Recording Media" Tom Coughlin, Ampex Corporation sdphln.ucsd.edu Abstract: Soft magnetic layers adjacent to the hard magnetic storage layer of recording media enhance the magnetic reproduction process resulting in greater areal densities and head performance. The soft magnetic "keeper" layer reduces the demagnetization field of the recorded transitions resulting in a narrower transition length. The reduced demagnetization field also increases the stability of the recorded transitions to thermal demagnetization. The thermal stability improvement has been demonstrated experimentally with low Mrt media at the University of Minnesota. This effect may make soft magnetic layers a necessary part of very high density magnetic recording media. Since the keeper layer shunts the transition flux, a bias field must be applied to the keeper layer in order to read-back the recorded signal. With an inductive head the bias field saturates a region of the keeper releasing and shaping the recorded transitions. The bias introduces asymmetries into the reproduced signal which are a function of the bias field. Both TPI and BPI improvements have been demonstrated using keepered media. The unsaturated keeper acts as a magnetic shield reducing the reproduce effects of magnetic discontinuities such as negative undershoots from finite pole tip heads as well as adjacent transition and track pick-up. There is evidence that the keeper layer may interact with head poles so as to reduce write to write variation in head output. Media transition noise is also reduced with an appropriate keepered media. With the current keeper layer materials and structure the keeper layer itself contributes minimal added noise to the recorded system. Recent work with SAL MR heads indicates that the keeper layer can be saturated by the MR element bias field. Keepered media may be able to improve the off-track performance of the MR heads. The unsaturated keeper surrounding the region saturated by the MR element bias field acts as a shield. This shield enhances the existing MR head magnetic shields and in addition shields the MR element from adjacent tracks. We believe that this technology can be extended to all magnetic recording systems to improve usable recording density and product performance.

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