Theory and Experiment in Magnetic Recording

The traditional dominance of gamma ferric oxide as the ferromagnetic constituent of recording media is currently being challenged by the development of new particles, such as chrome dioxide and metallic particles, as well as thin metallic films of high coercivities. These new materials allow for a large variation of the magnetic properties and the thickness of the recording surfaces, and offer considerably greater potential for recording optimization in high-storage applications. They have also brought about a renewed interest in the theory of magnetic recording, particularly pertaining to the correlation between the magnetic properties and recording performance. In this paper we discuss the present status of theory and experiment in magnetic recording. It is concluded that our present theoretical understanding is such as to adequately explain the geometrical aspects of the recording process—transducer to medium spacing, transducer gap length, and medium thickness—but less than adequate in characterizing the magnetic state of the recording media.