Electricity: measuring and testing – Magnetic – Magnetic information storage element testing
Patent
1997-01-30
1999-10-05
Snow, Walter E.
Electricity: measuring and testing
Magnetic
Magnetic information storage element testing
360 25, 369 58, G01R 3312, G01N 2772, G11B 502, G11B 2734
Patent
active
059630299
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.
REFERENCES:
patent: 4847558 (1989-07-01), Fisher et al.
"The Gaussian Beam", Fundamentals of Photonics, Saleh, et al, pp. 81-87,, 1991.
Niebuhr Frederick W.
Seagate Technology Inc.
Snow Walter E.
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