ABSTRACT
The heart of recording technology is for the process of information storage and retrieval. In addition to its obvious importance in different branches of science and engineering, it has become indispensable to our daily life. Typical recording equipment consists of a read/write head, a medium, a coding/decoding system, a data access system, and some auxiliary mechanical and electronic components. The head and medium are for data storage and retrieval purposes, and the coding/decoding system is for data error correction. At present, magnetic recording technology dominates the recording industry. It is used in the forms of hard disk, floppy disk, removable disk, and tape with either digital or analog mode. Magnetism is the result of uncompensated electron spin motions in an atom. Only transition elements exhibit this property, and nearly all practical interest in magnetism centers on the first transition group of elements and their alloys.
