Magnetooptical recording

In addition to the above inductive technologies for information storage, devices based on the Faraday or Kerr effects are being developed. The aim is to increase two of the most appreciated characteristics in storage technology devices data density and access time. The storage capacity of a magnetooptical disc is currently 600 MB (files, 1991). An additional characteristic of these methods is that the wear problem is virtually eliminated. 

The reading of the information is performed by means of a polarised, low-intensity laser beam, by detecting the rotation angle of the transmitted (Faraday effect) or reflected (Kerr effect) beam. Fig. 5.20(f)). In the case of reading by reflection, the magnetic film can be deposited on a reflecting 

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Thin-film media can be made by various technologies, eg, sputtered deposited Co—Cr—X films for longitudinal appHcations, laminated media for hard disk apphcation, metal evaporated tape, and multilayers for possible appHcations in magnetooptic recording. 

Luborsky, F.E. (1987) Amorphous transition metal-rare earth alloy films for magnetooptical recording. Materials Research Society Symposium Proceedings, 80 (Science and Technology of Rapidly Quenched Alloys) 375-394. 

Many specialised applications of magnetic materials involve the utilisation of ferrite thin films, such as magnetic and magnetooptic recording media, microwave devices in integrated circuits and coatings for microwave shielding. To prepare these ferrite thin fihns, a wide variety of techniques has been devised. 

Fig. 5.20. Magnetooptical recording technology (a) thermomagnetic writing (b) reading by means of the Kerr effect. (Adapted from Marchant, 1990.)...

Due to their impact on information storage technology, a brief account of materials for magnetic recording media and heads is presented. Materials for magnetooptical recording are also discussed. 

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