System and method for determining whether defect in perpendicular recording disk drive is from thermal asperity or defect in magnetically soft underlayer
US7271967B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 28, 2004 |
| Grant date | Sep 18, 2007 |
| Priority date | — |
| Expiry date | Aug 4, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B20/1816
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method for determining whether a spike in a read back signal from a read head positioned over a perpendicular recording disk having a magnetically soft underlayer (SUL) is caused by a defect in the SUL or by a thermal asperity (TA). A first read back signal with the spike is obtained in the absence of a local magnetic field near the read head. Then, a permanent magnet or electromagnet is used to induce a small local magnetic field by the read head, and a second signal is obtained. If the signals are substantially similar, a thermal asperity is indicated. Otherwise a defect in the 13 magnetically soft underlayer of the disk is indicated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.