Media testing technology for magnetic defects detection and measurement

As areal density increases towards TB/in² domain, improved detection capability of media defects become more critical. We have developed a media tester with concurrent multi-functional testing. Testing results using specially fabricated sample for missing pulse and optical surface analyzer measurement were compared. The former was found superior in detection sensitivity and resolution, and shown to be useful also for indirect detection of media surface physical variations. However the missing pulse approach needs to be correlated with other concurrent tests such as Laser Doppler Vibrometry and Acoustic Emission, so that spurious results can be eliminated. Such concurrent testing on a single tester is important towards providing an ldquoaccurate picturerdquo of the tested media surface and condition.