In the computer realm, magnetic recording is used on floppy disks, hard disks and magnetic tape as the main method for data storage. In this edition of How Stuff Works we will look at how magnetic recording works by focusing on cassette tapes and tape recorders, but the same technology applies to any form of magnetic recording. The tape itself is actually very simple. It consists of a thin plastic base material, and bonded to this base is a coating of ferric oxide powder. The oxide is normally mixed with a binder to attach it to the plastic, and it also includes some sort of dry lubricant to avoid wearing out the recorder.
Ferric oxide is another oxide of iron.
Fe 2 O 3 is the chemical formula for it and maghemite or gamma ferric oxide are common names for the substance. This oxide is a ferromagnetic material, meaning that if you expose it to a magnetic field it is permanently magnetized by the field. Audio tapes have gone through several format changes over the years. The original format was not tape at all, but actually was a thin steel wire. The wire recorder was invented in 1900 by Valdemar Poulsen in 1900.