Magnetic recording has been responsible for the widespread and inexpensive recording of sound and video. Despite the availability of other means of storing data, such as optical recording and semiconductor devices, flexible magnetic-recording media have advantages such as (1) low cost, (2) stable storage, (3) a relatively high data rate, (4) a relatively short seek time, and (5) high-volumetric information density.The first commercially available magnetic-recording tapes were produced in 1947 by the 3M Company. Since that time, magnetic tapes have developed rapidly for use in audio, video, and digital-data recording systems.The linear-analogue technique is commonly used for most audio recorders. The magnetic tape is transported at a speed of several cm/s over a stationary head. On the other hand, helical-scanning rotary heads were developed for video recording, which afforded a high head-to-tape speed of more than several m/s and high recording-density capabilities. However high relative speed causes wear of the tape. The success of a tape in actual use depends critically on its tribological properties.Magnetic media are divided into two groups: (1) particulate media where magnetic particles are dispersed in a polymer binder with some additives and coated onto the substrate and (2) thin-film media in which monolithic, magnetic thin films are deposited onto the substrate in vacuum. The overwhelming preponderance of media fabricated to date have been coated media. However continuous demand for increasingly higher recording density has led to thin-film media.