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Magnetic Smoothing and Signal Enhancement of Recording Media Coatings

IP.com Disclosure Number: IPCOM000052669D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Larson, TL: AUTHOR [+2]

Abstract

The fundamental method of aligning unoriented magnetic moments is to apply a magnetic field in the desired direction of orientation. The moments in "soft" magnetic materials, such as the coatings of recording media (e.g., iron oxide and chromium dioxide particles in plastic binders), tend to remain in the new orientation when the field is removed.

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Magnetic Smoothing and Signal Enhancement of Recording Media Coatings

The fundamental method of aligning unoriented magnetic moments is to apply a magnetic field in the desired direction of orientation. The moments in "soft" magnetic materials, such as the coatings of recording media (e.g., iron oxide and chromium dioxide particles in plastic binders), tend to remain in the new orientation when the field is removed.

We have observed auxiliary phenomena--surface smoothing and signal enhancement--when the field of a pair of permanent magnets 10 is placed in close proximity to a wet coating of CrO(2) particles 11 on a disk 12. The experimental arrangement is shown in Fig. 1 (top view) and Fig. 2 (side view). Gap 13 is filled with a nonmagnetic material. Shields 14 are permeable metal. In contrast with the alignment of moments, surface smoothing is greatest where the magnetic field is least uniform, i.e., at the ends 15 of gap 13 where the field gradient is largest. As the disk is rotated, the smoothed areas form concentric rings 16.

Test measurements provided two semi-quantitative results: (1) laser goniometer observations showed the smoothed areas to be at least twice as smooth as any other area of the same coating on the same disk, and (2) digital recording tests showed the signal amplitude in the smoothed areas to be 4-5 dB higher than in the unsmoothed areas.

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