Information Storage Materials, Magnetic

Abstract

AbstractMagnetic recording is the storage of information achieved through changing the magnetization of a recording medium using a magnetic field generated by the recording head. At the end of the nineteenth century a start was made to use magnetism and magnetic media to store information. The first demonstration of magnetic recording was at the World's Fair in Paris in 1900. From this time on, the magnetic recording medium has gone through dramatic improvements. The steel wire was replaced in the early 1930s by small spherical Fe particles and later by cubic Fe3O4. Since then great improvements have been made by changing the material and the shape and size of the particle.In 1949, γ‐Fe2O3acicular particles with a length of 0.5 µm and an aspect ratio of 10 were used. Compact cassette tape made from CrO2particles was introduced in 1966. From the early 1950s thin magnetic films have been proposed as a magnetic recording medium. Since then extensive research has been carried out and many thin‐film media have been proposed made by electroless and electrodeposition, vacuum evaporation, and sputtering. At present many recording media are prepared by vacuum deposition technologies; mostly hard disk applications for magnetic recording as well as magnetooptic recording. Sony presented the first evaporated tape for video application in 1989. The so‐called ME tapes have also been made for audio applications. An enormous amount of research is being carried out on the new hard disk media, mostly produced by sputtering, in order to obtain high densities. Since 1977 much research has been carried out on media proposed for the application of perpendicular magnetic recording.