Directly contactable disk for vertical magnetic data storage

Details Directly contactable disk for vertical magnetic data storage Directly contactable disk for vertical magnetic data storage

1997-01-23

1999-07-13

Evans, Jefferson

Dynamic magnetic information storage or retrieval

Record medium

Disk

205210, 428 653, G11B 562, C25D 534, B32B 302

Patent

active

059235110

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a disk for vertical magnetic data storage, in which the read/write process takes place perpendicular to the surface of the disk, and which can be contacted directly by a read/write head, as well as a process for the manufacture of such a disk.
The technique of vertical magnetic data recording allows for higher bit densities than horizontal recording. For vertical recording, a thin magnetic layer is required, in which the easy axis is located perpendicular to the surface of the disk. Such a magnetic layer can be created with more or less satisfactory results by separation processes. Problems arise, however, with the selection of the material, since no suitable material is available which simultaneously possesses the optimum magnetic properties and the optimum abrasion properties. Vertical magnetic data recording, in which the read/write head comes into direct contact with the storage disk, is therefore excluded, or requires an additional protective layer, which in turn decreases the bit density.
The improvement of the magnetic properties, namely an increase in the anisotropy, can be achieved if the magnetizable material is located in pores in the carrier substrate. A suitable anisotropic magnetic recording material for the vertical storage of information, with magnetic particles arranged perpendicular to the carrier substrate is known from the German public disclosure document 23 09 594. With this known arrangement, the magnetic storage material is applied in aluminium oxide micropores, which are located perpendicular to the recording carrier medium. The recording carrier medium, in general the substrate, consists primarily of aluminium or an aluminium alloy, the surface of which is provided with these pores by anodic oxidation. These pores are then filled with magnetic material in an electrochemical process. The pores have low thickness in relation to their length, with the result that the magnetic material possesses a shape anisotropy which is directed perpendicular to the plane of the recording carrier medium, and therefore contains a vertical magnetisation direction. For preference, the magnetic substance is packed in every pore only as far as just below the pore aperture. If the magnetic substance fills out the pore aperture completely, the abrasion at the points of the surface of the magnetic recording material which come in contact frequently with the magnetic head, forms a powder out of the oxide film and the magnetic substance, which from time to time may impair the recording.
With this known magnetic recording carrier substance, the substrate, i.e. the core of the recording carrier, which also determines its mechanical strength, consists of aluminium or an aluminium alloy. Enclosures in the substrate material, which do not consist of aluminum, i.e. in general external phase enclosures, exert a magnetic interference of such a nature that interference may occur during the recording. The carrier material or the substrate determines the mechanical strengths in particular when solid magnetic disks are under consideration. If aluminium is used, the carrier may in this case consist solely of technical aluminium or a technical aluminium alloy, and not of pure aluminium, since pure aluminium is very soft. With the given degree of purity of technical alloys, a coarse limit surface is created between the metal and the aluminium oxide during the anodizing process. This leads to a situation in which the magnetic particles, arranged perpendicular and partially rod-shaped, are of different lengths and therefore have different magnetic properties. In particular, the pores feature fluctuations in diameter. This in turn incurs disadvantageous consequences for the recording reproduction process.
An improved surface is obtained with the storage medium described in the German public disclosure document 33 28 839. In this case, a soft magnetic layer is first applied on a substrate, and a carrier layer of non-magnetic material laid on this. In the carrier layer, made of plastic, pores are create

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