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Ferromagnetodynamics: The dynamics of magnetic bubbles, domains and domain walls
JOURNAL
OF MAGNETIC
RESONANCE
49, 179-180
(1982)
Book Reviews Ferromagnetodynamics: The Dynamics of Magnetic Bubbles, Domains and Domain Walls, T. H. O’Dell. Wiley, New York, 1981. 230 pages. $54.95.
The author threads together a large collection of theory and experimental data under the general term, “ferromagnetodynamics.” Magnetic resonance and spin waves involve relatively small perturbations of the magnetization on a time scale usually less than lop9 sec. Ferromagnetodynamics, as defined by O’Dell, is concerned, on the other hand, with very large changes of magnetization, a complete reversal, for example, that may occur over a distance of less than lop6 min but on a time scale that is usually longer than 10d9 sec. In this scholarly work, in which over 400 references are cited, the author unfolds an understanding of magneticdomain reversal processes that has emerged over the past 75 years, but with particular emphasis over that of the past 10 years or so. The last decade, of course, includes the emergence of magnetic-bubble technology and its application to digital memory. Bubble memories in one format or another have been commercially available for about five years now, with four or five competing manufacturers presently producing worldwide. Bubble memories are designed with a serial or sequential kind of organization (they are not random-access) typically in modules of order of a megabit. In today’s environment of competition among alternative memory technologies, magnetic bubbles have the advantages of nonvolatility, high reliability even in hostile environments, and compactness. Thus, their main applications include their use in airborne equipment, numerical controllers, portable computers and terminals, and remote data collection. None of the engineering design or the technology of bubble memories is addressed in this book, but the physics of magnetic-bubble motion is explained in detail. A nonmathematical, historical overview of domain-wall dynamics from the time of the first concept of magnetic domains up until the present is given in the first chapter. The four remaining chapters include the Landau-Lifshitz equation, straight-wall motion in magnetic-bubble films, magnetic-bubble domain dynamics, and the ferromagnetodynamics of conducting media. There is a comprehensive author index with citations carefully indicated. This rather specialized subject is not for everyone, but O’Dell has made a significant contribution by establishing a common theoretical basis to explain magnetic-reversal processes in a wide variety of media, from the Sixtus-Tonks experiments on Ni-Fe wires in the early 1930s to the mobility of bubbles with complex wall structures in the late 1970s. The style in which the book is written makes it quite readable, and the reader can follow the main thrust of the author’s ideas without having to work out the mathematical details. Advanced students and researchers in the field of technical magnetism and magnetic bubbles may find this book particularly interesting. J. K.
WATSON
University
of Florida
179 0022-2364/82/100179-02$02.00/0 Copyright 0 1982 by Academic Press, Inc. All rights of reproduction in any form resewed.
OF MAGNETIC
RESONANCE
49, 179-180
(1982)
Book Reviews Ferromagnetodynamics: The Dynamics of Magnetic Bubbles, Domains and Domain Walls, T. H. O’Dell. Wiley, New York, 1981. 230 pages. $54.95.
The author threads together a large collection of theory and experimental data under the general term, “ferromagnetodynamics.” Magnetic resonance and spin waves involve relatively small perturbations of the magnetization on a time scale usually less than lop9 sec. Ferromagnetodynamics, as defined by O’Dell, is concerned, on the other hand, with very large changes of magnetization, a complete reversal, for example, that may occur over a distance of less than lop6 min but on a time scale that is usually longer than 10d9 sec. In this scholarly work, in which over 400 references are cited, the author unfolds an understanding of magneticdomain reversal processes that has emerged over the past 75 years, but with particular emphasis over that of the past 10 years or so. The last decade, of course, includes the emergence of magnetic-bubble technology and its application to digital memory. Bubble memories in one format or another have been commercially available for about five years now, with four or five competing manufacturers presently producing worldwide. Bubble memories are designed with a serial or sequential kind of organization (they are not random-access) typically in modules of order of a megabit. In today’s environment of competition among alternative memory technologies, magnetic bubbles have the advantages of nonvolatility, high reliability even in hostile environments, and compactness. Thus, their main applications include their use in airborne equipment, numerical controllers, portable computers and terminals, and remote data collection. None of the engineering design or the technology of bubble memories is addressed in this book, but the physics of magnetic-bubble motion is explained in detail. A nonmathematical, historical overview of domain-wall dynamics from the time of the first concept of magnetic domains up until the present is given in the first chapter. The four remaining chapters include the Landau-Lifshitz equation, straight-wall motion in magnetic-bubble films, magnetic-bubble domain dynamics, and the ferromagnetodynamics of conducting media. There is a comprehensive author index with citations carefully indicated. This rather specialized subject is not for everyone, but O’Dell has made a significant contribution by establishing a common theoretical basis to explain magnetic-reversal processes in a wide variety of media, from the Sixtus-Tonks experiments on Ni-Fe wires in the early 1930s to the mobility of bubbles with complex wall structures in the late 1970s. The style in which the book is written makes it quite readable, and the reader can follow the main thrust of the author’s ideas without having to work out the mathematical details. Advanced students and researchers in the field of technical magnetism and magnetic bubbles may find this book particularly interesting. J. K.
WATSON
University
of Florida
179 0022-2364/82/100179-02$02.00/0 Copyright 0 1982 by Academic Press, Inc. All rights of reproduction in any form resewed.