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Browse Prior Art Database

Disk Asperity Detector

IP.com Disclosure Number: IPCOM000046724D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Fontana, RE: AUTHOR [+3]

Abstract

Magnetoresistive (MR) heads, i.e., a thin film inductive head with a magnetoresistive material/structure integrated into the gap region of an inductive head, have been used for the detection of surface defects (asperities) on rigid disk media. The detection is based on the principle that the resistance of the MR stripe, like any metal, changes with temperature. Frictional heat generated during a head/disk contact gives rise to a temperature spike at the MR element. The contact event is recorded by measuring the resistance change of the element. To date, all asperity detection experiments used integrated structures which were naturally optimized for the detection (i.e., read) of magnetic information. Fig. 1 shows this MR structure. The MR material is NiFe or layers of NiFe and metals such as Ta, NiFeRh, FeMn, Pd.

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Disk Asperity Detector

Magnetoresistive (MR) heads, i.e., a thin film inductive head with a magnetoresistive material/structure integrated into the gap region of an inductive head, have been used for the detection of surface defects (asperities) on rigid disk media. The detection is based on the principle that the resistance of the MR stripe, like any metal, changes with temperature. Frictional heat generated during a head/disk contact gives rise to a temperature spike at the MR element. The contact event is recorded by measuring the resistance change of the element. To date, all asperity detection experiments used integrated structures which were naturally optimized for the detection (i.e., read) of magnetic information. Fig. 1 shows this MR structure. The MR material is NiFe or layers of NiFe and metals such as Ta, NiFeRh, FeMn, Pd. This prior-art design has several limitations when used for asperity detection. The MR/gold contacts are part of the thermally active region. Any contact resistance reduces the overall sensitivity of the detector. If the disk media has been written, magnetic transitions will contribute a magnetoresistive component to the resistance change of the structure, reducing detector sensitivity. There is little flexibility in tailoring the total resistance of the structure to match power supply impedances and to optimize signal/noise for sensitivity improvement. Described here are integrated structures which are optimized for asperity detection using thermally induced resistance changes. These structures are different from the MR-type asperity detectors because the designs do not have the requirement of...