This volume in the Academic Press Electromagnetism series is the second edition of the book on magneto-resistive heads. This book is written by John C. Mallinson, who is one of the leading experts worldwide in the area of magnetic recording. He is well known and highly regarded in the magnetics community for his many important contributions to the field of magnetic data storage as well, as for his well-written and influential books on magnetic recording. This second edition of his previous book on magneto-resistive heads reflects the phenomenal and explosive progress in magnetic storage technology where anisotropic magneto-resistive heads were quickly displaced by giant magneto-resistive heads, spin valves. Naturally, this edition contains many newly written chapters related to giant magneto-resistive heads. These chapters cover such new topics as synthetic antiferromagnet and ferrimagnet multilayer technology, magnetization fluctuation noise in small giant magneto-resistive heads, colossal magneto-resistance and spin dependent tunneling phenomena and their relevance to the future development of magnetic recording.