The outstanding feature of materials research in the eighties has been the convergence of basic research and practical application, leading to ever shorter cycles of innovation. This is especially true of materials which form the basis of key technologies. The mass storage units of the next generations of computers will be based on optical processes having a storage density which exceeds that of all hitherto known storage techniques that are practicable from the technical standpoint. In view of the fact that since 1982 read-only memories in the form of compact discs (CD-ROM) have become very successful in the field of audio electronics, research and development are now concentrated on materials for write-once (WORM) and erasable (EDRAW) storage systems. Suitable materials for optical data storage are substances in which data markings can be recorded and deleted respectively using semiconductor lasers. Materials development is centered on the synthesis of infrared-absorbing dyes for WORM memories and the production of rare earth/transition metal alloys for magneto-optical data recording. An introduction to CD-ROM technology will be followed by an overview of the state of development of the most important storage materials which are currently available commercially, and then the properties of these materials will be discussed with reference to selected examples.

Materials for Optical Data Storage

There is provided a magnetic medium in which the non-magnetic layer is a nickel-copper-phosphorus film containing 20 to 65 wt% of copper, which layer is formed by electroless plating It does not become magnetic even after heat treatment at 200 DEG C or above

Magnetic recording medium

Magnetic recording media are controllably textured, particularly over areas designated for contact with data transducing heads. In connection with rigid media, the process includes polishing an aluminum nickel-phosphorous substrate to a specular finish, then rotating the disc while directing pulsed laser energy over a limited portion of the radius, thus forming an annular head contact band while leaving the remainder of the surface specular. The band is formed of multiple individual laser spots, each with a center depression surrounded by a substantially circular raised rim. The depth of the depressions and height of the rims are controlled primarily by laser power and firing pulse duration. The shape of individual laser spots can be altered by varying the laser beam inclination relative to the disc surface. On a larger scale, the frequency of firing the laser in combination with disc rotational speed controls the pattern or arrangement of laser spots. The smooth, rounded contours of the depressions and surrounding rims, as compared to the acicular character of mechanically textured surfaces, is a primary factor contributing to substantially increased durability of laser textured media.

Selectively textured magnetic recording media

A magnetic recording medium with a recording layer composed of a magnetic film formed on a substrate, in which an intermediate layer and a plasma-polymerized film are formed in succession on the recording layer.

A novel bidirectional magnetic microactuator using electroplated permanent magnet arrays has been designed, fabricated and characterized. To realize a bidirectional microactuator, CoNiMnP-based permanent magnet arrays have been fabricated first on a silicon cantilever beam using a new electroplating technique. In the fabricated permanent magnets, the vertical coercivity and retentivity have been achieved up to 87.6 kA/m (1100 Oe) and 190 mT (1900 G), respectively by applying magnetic field during electroplating. A prototype bidirectional magnetic microactuator has been realized by integrating an electromagnet with a silicon cantilever beam, which has permanent magnet arrays on its tip. By applying a do current of 100 mA and altering its polarity, bidirectional motion on the tip of the cantilever beam has been successfully achieved in the deflection range of /spl plusmn/80 /spl mu/m.

A bidirectional magnetic microactuator using electroplated permanent magnet arrays

Magnetic storage means which may be a disc having a magnetic storage layer coated with a protective layer. The protective layer, which is preferably an inorganic oxide material, protects the magnetic storage layer from corrosion. A lubricant is applied to the protective layer and serves to reduce wearing due to frictional drag between the disc and a cooperating magnetic head (or heads). The lubricant is oriented so as to make very good adherence with the oxide sublayer and thereby prevent removal of the lubricant through continued use and/or cleaning.

Magnetic record member and process for manufacturing the same

The perpendicularly oriented crystal structure conditions of electroless plated film for high density perpendicular recording media were investigated mainly by (002) plane rocking curves and cross sectional SEM observation. A highly oriented narrow dispersion of c‐axis orientation normal to the surface plane was consequently obtained, and the columnar structure of hcp crystal with ca. 0.05 μm diam was confirmed. As a result of preparing disks A and B, which were chemically plated from an optimum bath and a more improved bath, respectively, the recording characteristics with a combination of ring head were obtained as recording densities of for disk A and 25,000 FRPI for disk B, in spite of a relatively thick magnetic medium. The di‐pulse waveforms, which are characterized with perpendicular recording, were observed at low bit recording density. It was indicated by the above results that the chemically plated Co alloy films are applicable as a perpendicular recording medium.

A Preparation of Perpendicular Magnetic Recording Media by an Electroless Plating Method

The thin film magnetic medium of a magnetic disc, and the read/record head employed with the disc are both protected from abusive use and physical damage as well as chemical damage (including damage due to heat and/or humidity) by a polysilicate layer, formed upon the magnetic medium. Inexpensive methods of forming the protective film (which methods lend themselves to mass production) are described. These methods are a small fraction of the cost of present day techniques.

Magnetic record member

Process for manufacturing a magnetic record member

PURPOSE: To increase the durability of a protective film, by making lower projections in height and reducing the number through the formation of nonmagnetic metal thin film on a nonmagnetic substrate by Ni-Cu-P plating. CONSTITUTION: Electroless plating is performed for Ni-Cu-P alloy on a nonmagnetic substrate by Ni-Cu-P electroless plating liquid. Next, after forming metallic and magnetic thin film on it, a protective layer is formed on it. COPYRIGHT: (C)1981,JPO&Japio

Yoji Suganuma

Papers

Magnetic record member and process for manufacturing the same

A Preparation of Perpendicular Magnetic Recording Media by an Electroless Plating Method

Magnetic record member

Process for manufacturing a magnetic record member

Magnetic recording body