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Noise in Disk Data-recording Media

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2 Author(s)
Su, J.L. ; IBM General Products Division Laboratory, Monterey and Cottle Roads, San Jose, California 95193, USA ; Williams, M.L.

Measurements were made of recording medium noise in erased disks using an in-contact magnetoresistive element and an inductive head supported on an air bearing slider. Four types of coatings on aluminum disks were examined: thin, transition-metal alloy film, CrO2, FeCo particle, and γ-Fe2O3. Results obtained by means of three measurement techniques are in qualitative agreement and indicate that: (1) dc-erased noise of alloy film disks is 14 to 20 dB lower than that of particulate disks measured; (2) dc-erased noise of particulate disks measured is 6 to 16 dB above their bulk-erased noise; (3) although dc noise of particulate disks increases with write current, dc noise of alloy film disks is independent of write current; (4) the shapes of the noise spectra are similar in dc-erased particulate γ-Fe2O3 disks and FeCo particle coated disks; and (5) significant modulation noise is detected on particulate disks but not on alloy film disks. The observed dc-erased noise spectrum is compared with the model for small particle noise and is then used to estimate the size of particle agglomerates or voids.

Note: The Institute of Electrical and Electronics Engineers, Incorporated is distributing this Article with permission of the International Business Machines Corporation (IBM) who is the exclusive owner. The recipient of this Article may not assign, sublicense, lease, rent or otherwise transfer, reproduce, prepare derivative works, publicly display or perform, or distribute the Article.  

Published in:

IBM Journal of Research and Development  (Volume:18 ,  Issue: 6 )