The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 05, 1999
Filed:
Jan. 30, 1997
Jason L Pressesky, Menlo Park, CA (US);
Seagate Technology, Inc., Scotts Valley, CA (US);
Abstract
A system for magnetically evaluating magnetic data storage media includes a spindle for rotatably supporting magnetic disks, a read/write transducer, and an erasing transducer, both supported for radial movement relative to the disk. The read/write transducer records a sequence of magnetically isolated transitions. When sensing the sequence, the read/write transducer generates a fringing field signal which is low pass filtered and RMS processed to provide a voltage proportional to the remanence-thickness product. The erasing transducer is a ring head transducer having a substantially larger gap and transducer/disk spacing as compared to an aerodynamically supported transducer. Consequently a Hall effect probe is positionable within the gap to directly measure the magnetic intensities of erase fields. Coercivity is determined by applying the erase fields in a sequence of increasing intensities, with each application followed by a measurement of the remanence-thickness product, until the remanence-thickness product has been reduced by one-half. The read/write transducer can be aerodynamically supported to more accurately replicate transitions encountered during normal use, or can be of the ring head type to enable testing of the disk at intermediate fabrication stages.