Table Of ContentAn IEEE Press Classic Reissue
THE PHYSICAL PRINCIPLES
OF MAGNETISM
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An IEEE Press Classic Reissue
THE PHYSICAL PRINCIPLES
OF MAGNETISM
Allan H. Morrish
Department of Physics and Astronomy
University of Manitoba, Canada
IEEE Magnetics Society, Sponsor
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Original edition in 1965, published by John Wiley & Sons, Inc.
Reprinted in 1980 byRobert E. Krieger Publishing Company, Inc.
© 2001 by The Institute of Electrical and Electronics Engineers, Inc.
3 Park Avenue, 17th Floor, New York, NY 10016-5997
All rights reserved. No part of this book may be reproduced in any form,
nor may it be stored in a retrieval system or transmitted in any form,
without written permission from the publisher.
10 9 8 7 6 5 4 3 21
ISBN 0-7803-6029-X
IEEE Order No. PC5877
Library of Congress Cataloging-in-Publication Data
Morrish, Allan H.
The physical principles of magnetism / Allan H. Morrish.
p. cm.
Originally published: New York : Wiley, 1965, in series: Wiley series on the
science and technology of materials.
"An ΓΕΕΕ Press classic reissue."
"IEEE order no. PC5877"~T.p. verso.
Includes bibliographical references and indexes.
ISBN 0-7803-6029-X
1. Magnetism. I. Title.
QC753.2 .M67 2001
538»dc21
00-053912
To My Parents
Foreword to the Classic Reissue
The IEEE Magnetics Society has embarked on a program of reissues of clas-
sic works in magnetism. These books have served as an invaluable resource for
understanding magnetic phenomena. The Physical Principles of Magnetism by
Allan Henry Morrish is such a classic—a comprehensive introduction to all
aspects of magnetism. Since its publication in 1965, it has been used by many
scientists to learn the basics of magnetism in considerable depth. The corrected
reissue is a welcome addition to this much-needed archival series.
Dr. Morrish presents an excellent introduction to the physics and mathemat-
ics of magnetism without oversimplification. Although great progress has been
made in technology in the 35 years since it first appeared in print, the basic
principles of magnetism are unchanged. This respected and timeless classic
book clearly elucidates these principles.
Dr. Morrish is a distinguished professor of physics at the University of
Manitoba. He is a fellow of The Royal Society of Canada and The Institute of
Physics (U.K.), as well as a former fellow of The American Physical Society.
Also, he was president of The Canadian Association of Physicists and was
awarded their gold medal for achievements in physics. A prolific researcher, Dr.
Morrish has written over 250 papers and served on many national and interna-
tional committees.
It is with great pleasure that we welcome this book back in print.
Edward Delia Torre
The George Washington University
President of the IEEE Magnetics Society
Preface
Whatever else may be said concerning the two decades following World
War II, they have been wonderful years for science. All of the scientific
countries of the world have contributed to the great increase in knowledge.
Although advances have been made in almost all areas, some have been
favored over others. One of the subjects that has received the greatest
attention is that of magnetism. Although the appearance of a vast amount
of literature is in itself laudable, it has created educational problems.
The scientist or engineer who desires or requires an integrated knowledge
of magnetism has found it increasingly difficult to satisfy this need. This
book was written with such readers primarily in mind.
The material between these covers has formed the basis for several
solid state courses offered at the University of Minnesota since 1958.
Some of the more elementary parts have been employed for the third
quarter of a first course in solid state physics. However, the major use of
this text has been as a three-quarter graduate course in magnetism. The
students attending the lectures have come from chemistry, physics,
electrical engineering, physical metallurgy, and geophysics departments.
Since the backgrounds of the audience varied so much, the course was
developed by starting as far as possible from first principles. However,
it was necessary to begin somewhere, and consequently, first courses in
solid state physics and quantum mechanics were usually assumed as
prerequisites.
Magnetic phenomena are discussed both from an experimental and
theoretical point of view. The plan has been first to present the underlying
physical principles and then to follow up with appropriate macroscopic
or microscopic theories. Although quantum mechanical theories are
given, a phenomenological approach is emphasized. More than half the
vli
viii PREFACE
book is devoted to a discussion of strongly coupled dipole systems, and
in this area the molecular field theory is stressed. The principles and
theories have been illustrated by selections from the experimental data,
and various tables have been included in. an attempt to give some idea of
the scope of the literature. Very few references to 1964 papers are included
because of publication deadlines.
The utter impossibility of completely surveying all aspects of the subject
may be illustrated by considering the 1964 Magnetic Materials Digest.1
This publication, which attempts to summarize the 1963 literature per-
taining to fundamental studies of ordered magnetic materials, contains
more than 1700 references! The particular topics chosen to be discussed
at greatest length in this book were determined, as it is usually put, by
my own interests. This, of course, really means my own knowledge,
experience, talents, and limitations as shaped by contact with colleagues,
teaching assignments, and availability of research and travel grants. The
coverage of some topics, for example alloys and superconductivity,
inadequately reflects the number and extent of current investigations.
Other topics, for example, magnetohydrodynamics, group theoretical
analysis, and the magnetoelectric effect, have been completely omitted.
Nevertheless, the book is rather long and indeed contains more material
than can normally be covered in a one-year course.
The question of notation has been a vexing problem. In a book as
comprehensive as this one, there are simply not enough symbols to go
around. A partial solution has been sought in the use of different kinds
of type for the same letter. For example, μ and μ represent the dipole
magnetic moment and the permeability, H and 3t represent the magnetic
field and Hamiltonian, and D, D, and Ϊ) represent the demagnetizing
factor, the crystal field spin parameter, and the Dzialoshinski vector,
respectively. Even so, it was found necessary sometimes to employ the
same symbol for more than one quantity; it is only hoped that the context
will reduce, if not entirely remove, the danger of ambiguity. Although in
general I have tried to adhere to the symbols commonly found in the
literature, some deliberate departures have been made. In publications
on nuclear magnetic resonance, and to some degree in electron para-
magnetic resonance, T with some subscript denotes relaxation time.
However, I prefer to reserve T for either temperature or period of time
and have therefore taken the liberty of representing relaxation times by
T plus a subscript; this usage at least has the merit of being consistent
with that in all other branches of science and engineering. Other, though
less important examples, include the use of M for the magnetization
H
1 A. H. Morrish, R. J. Prosen, and S. M. Rubens, editors, 1964 Magnetic Materials
Digest, M. W. Lads Publishing Co., Philadelphia, Pa. (1964).
PREFACE ix
along the direction of an applied field, Ηχ for the amplitude of an alter-
nating magnetic field, H for the effective magnetic field, H for
e m
the molecular field, J for an exchange interaction constant, T for the
e FN
Neel temperature of a ferrimagnet, and N with some subscript for the
Weiss molecular field constants. For the Bohr magneton a choice between
μ and β was possible; I have selected μ mainly because ß also represents
Β Β
an angle or the relativistic quantity v\c. I have substituted the term
"uncompensated poles" for "free poles," since the latter may be taken
to imply the existence of monopoles, and they have never been observed
in nature. The phrase "intensity of magnetization," common in the
British literature, has been eliminated on the grounds that it is both
inappropriate and inept. The symbol e for the elementary electric charge
represents either type; that is, a negative number is to be substituted for
an electron and a positive number for a proton or positron. Except as
otherwise noted, the gaussian cgs system of units is employed.
There remains the pleasant task of thanking those who have played
some role in the production of this book. I am very grateful to Professor
A. J. Dekker, now at Groningen, The Netherlands, who first interested
me in doing research in solid state physics and who encouraged me to
write this book. I have been fortunate in having Professor W. F. Brown,
Jr., as a colleague during part of my tenure at the University of Minnesota.
The discussions we have had have left their imprint on a number of
these pages. In addition, a critical reading of the first chapter by Dr.
Brown has led to its improvement. The response and comments of my
graduate students have greatly aided me in the removal of errors, incon-
sistencies, and obscurities. They have also demonstrated that almost all
the problems are soluble. I am indebted to the many publishers and
individuals who have given me permission to reproduce figures and tables;
these sources are acknowledged at the pertinent places in the text. Finally,
I wish to thank my wife for her help with the arduous tasks of proofreading
and index preparation.
University of Manitoba ALLAN H. MORRISH
Winnipeg, Canada
April 1965
