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Disk Coating Orienting Electromagnet

IP.com Disclosure Number: IPCOM000045897D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Hagopian, JJ: AUTHOR

Abstract

Perpendicular recording disks with particulate magnetic coatings must be subjected to a uniform perpendicular field while the "wet" disk is drying. A swinging electromagnet pair for this use is disclosed. The principal advantage of perpendicular recording is the ability to operate at very high linear bit densities without having to use extremely thin magnetic disk coatings. A less obvious advantage is that, unlike the situation with longitudinal recording, it is possible to apply the coating orienting field uniformly and at once over the entire disk area by means of an electromagnet pair, as shown in the figure.

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Disk Coating Orienting Electromagnet

Perpendicular recording disks with particulate magnetic coatings must be subjected to a uniform perpendicular field while the "wet" disk is drying. A swinging electromagnet pair for this use is disclosed. The principal advantage of perpendicular recording is the ability to operate at very high linear bit densities without having to use extremely thin magnetic disk coatings. A less obvious advantage is that, unlike the situation with longitudinal recording, it is possible to apply the coating orienting field uniformly and at once over the entire disk area by means of an electromagnet pair, as shown in the figure.

Two rotatable bipolar electromagnets 12a and 12b with semicircular poles swing apart to allow placing a "wet" coated disk 13 on a spindle. The electromagnets are then swung together to straddle the entire disk, and current is supplied to the windings to create the perpendicular orienting fields while the disk coating is drying, and the disk can be held stationary or rotated during this time. The electromagnet gaps are tapered to ensure uniform field strength.

For the maximum degree of perpendicular orientation the coating's magnetic particles must be needle-like and smooth. Iron oxide chromium dioxide and cobalt-doped iron oxide particles should prove satisfactory in coatings subjected to the perpendicular orienting technique described.

With longitudinal recording, the magnetic particles in a "wet" coating tend to rela...