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Perpendicular Recording Media With Patterned Magnetic Underlayer to Reduce Readback Signal Envelope Modulation

IP.com Disclosure Number: IPCOM000038773D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Sanders, IL: AUTHOR

Abstract

Perpendicular recording media for use with pole-type head configurations commonly employ two layers: a magnetic storage layer with perpendicular anisotropy and a soft-magnetic underlayer to provide a flux return path for the head, as depicted in Fig. 1. The magnetic storage layer is typically a thin film cobalt-chromium (CoCr) alloy or a coating of barium ferrite particles dispersed in an organic binder. The underlayer is typically a nickel-iron (NiFe) alloy. In order to reduce the readback signal envelope modulation resulting from in-plane anisotropy in the underlayer, the underlayer should be made as nearly isotropic as possible.

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Perpendicular Recording Media With Patterned Magnetic Underlayer to Reduce Readback Signal Envelope Modulation

Perpendicular recording media for use with pole-type head configurations commonly employ two layers: a magnetic storage layer with perpendicular anisotropy and a soft-magnetic underlayer to provide a flux return path for the head, as depicted in Fig. 1. The magnetic storage layer is typically a thin film cobalt-chromium (CoCr) alloy or a coating of barium ferrite particles dispersed in an organic binder. The underlayer is typically a nickel-iron (NiFe) alloy. In order to reduce the readback signal envelope modulation resulting from in-plane anisotropy in the underlayer, the underlayer should be made as nearly isotropic as possible. A method of reducing readback signal envelope modulation is to use a photolithographically defined pattern in the underlayer, wherein the pattern generally corresponds to the data tracks in the storage layer. In the case of a disk, the shape anisotropy introduced by the pattern forces the magnetization in the underlayer to lie circumferentially along the track direction. This produces a uniform response around the track. The patterning consists of defining narrow circular "tracks" in the underlayer itself, with a pitch equal to, or less than, the recorded track pitch. For example, in a 2000-track-per-inch system the patterned tracks would be 10 mm in width separated by 2 mm gaps, as shown in Fig. 2. In this manner the width of...