Particulate magnetic recording media

Magnetic recording media have dominated the arena of peripheral information storage throughout its 50 year-old history. They can be classified into particulate and thin film types, with the former dominating the flexible storage media area (tape and floppy disks) while the latter has become the exclusive choice for rigid disk media. In this paper we review the properties, application areas, and the status of development in particulate magnetic recording media. In earlier years, the development of advanced particulate media was aimed at high coercivity, high magnetization, smaller and better-dispersed and oriented particles, and thinner magnetic layer coatings. Because the thinness of the magnetic layer is of extraordinary importance for high density recording performance, it was expected that the ultimate optimization would lead to thin metal films of high magnetization and high coercivity prepared by electron beam evaporation or sputtering. This expectation has not been realized for various technological and economic reasons: . Did not take into account the disadvantages of thin film media compared to particulate media with regard to cost, wear performance, corrosion, and media noise. . The development of double-coated particulate media which permit the fabrication of very thin magnetic coatings, thus obviating the thinness advantage of metal film media. . The extraordinary developments in high sensitivity magnetoresistive sensors (MR, GMR, Spin valves) which de-emphasize the importance of high magnetization but emphasize the importance of low media noise. The interplay of these considerations has resulted in the continued dominance of particulate media, even though thin film tapes are beginning to establish a presence in digital video applications. Among the advanced tape media, Barium ferrite has perhaps the best potential to achieve the ultimate recording densities, and to transition to perpendicular recording.