BIBLIOGRAPHY

S. V. Vonsovskii. The Modern Theory of Magnetism. State Publishing House of Technical-Theoretical Literature, Moscow–Leningrad, 1952, 440 pp., price 12 rubles 50 kopecks.

In our literature there has hitherto been no book that would give an account of modern views on all the principal branches of the theory of magnetic phenomena. The existing monographs are either obsolete or devoted to the consideration of only individual areas of the theory of magnetism. The monograph under review*), written by one of the leading Soviet magnetologists, should fill this gap in our literature on magnetism. In addition, in a number of Western monographs, with the exception of V. K. Arkad’ev’s book Electromagnetic Processes in Metals, published in 1935–1936, the role of Russian and Soviet scientists in the development of the science of magnetism is reflected quite inadequately. In the book under review, due attention is paid to this question.

The book consists of three parts and brief prefaces and an introduction. The first part (61 pp.) presents questions of atomic magnetism: the magnetic properties of the electron, the electron shells of the atom, nucleons, and atomic nuclei. The question of the nature of the magnetic moment of the electron and its anomaly (§§ 1 and 4) is treated rather fully. The principal magnetic effects in atoms (the Zeeman effect, magnetic resonance, nuclear induction) are clearly set forth. The method of polarizing a neutron beam, which is acquiring ever greater importance for ferromagnetic investigations, is discussed.

In the second part, occupying 123 pages, the diamagnetic and paramagnetic properties of matter are considered. After a brief exposition of the magnetic action of current, the properties of magnets, the foundations of the thermodynamics of magnets, and the classification of magnets (§§ 5, 6), diamagnetism is discussed. Both the classical derivation of the formula for diamagnetic susceptibility and Van Vleck’s quantum theory are presented. The experimental methods for investigating diamagnets are then considered. The diamagnetism of metals is examined in especially great detail, an area in which Soviet physicists have done much work (the work of B. G. Lazarev and his collaborators). The magnetic properties of superconductors are set forth clearly and with sufficient completeness.

Paramagnetism is likewise considered first from the classical and then from the quantum point of view, after which the principal experimental data are analyzed. In the tenth paragraph the processes accompanying the demagnetization of paramagnets are considered, making it possible to obtain

*) It was based on an article by the same author published in UFN, XXXV, 514 (1948); XXXVI, 30 (1948); XXXVII, 1, 137 (1949).

low temperatures about 0.003° above absolute zero. Time-dependent processes in paramagnets (paramagnetic relaxation) are considered very briefly, but on this question there is a Russian translation of Gorter’s monograph. In the last paragraph of the second part the theory of magneto-optical phenomena is briefly considered: the magnetic rotation of the plane of polarization and double refraction in a magnetic field. As usual, the author first considers the classical and then the quantum theory of the phenomena. The Zeeman effect was considered in the second paragraph of the first part.

More than half of the book, 224 pages, is devoted to ferromagnetism. In the introduction the importance of the work of the Russian scientists A. G. Stoletov and B. L. Rozing in creating the foundations of the modern theory of ferromagnetism is emphasized. The need for dividing the theory of ferromagnetism into two parts is clearly indicated: the theory of spontaneous magnetization at temperatures below the Curie point and the theory of ferromagnetic domains, or the theory of the technical magnetization curve. In accordance with this division, the subsequent exposition is also constructed. After a brief phenomenological theory of the molecular field of Rozing–Weiss and a thermodynamic theory of ferromagnetic transformations, the author considers the exchange theory of ferromagnetism, whose basic ideas were first developed by the Soviet physicist Ya. I. Frenkel.

The most recent development of the theory of ferromagnetism proceeds along the path of creating a many-electron model. Great credit for the development of this theory belongs to S. V. Vonsovskii and his collaborators, as well as to other Soviet physicists: Akhiezer, Bogolyubov, Tyablikov, and others. Foreign magnetologists Slater, Van Vleck, Stoner, and others are trying to develop the theory on the basis of a one-electron model; the groundlessness of these attempts has been convincingly shown by S. V. Vonsovskii. In view of the mathematical difficulties that arise when considering the complete many-electron model, the author considers a simplified model in which the $d$-electrons responsible for ferromagnetism are treated according to the many-electron exchange model, while the $s$-electrons responsible for electrical conductivity and other metallic properties are treated according to the one-electron model, but the exchange interaction between the $d$- and $s$-electrons is taken into account. Such an interpretation enabled S. V. Vonsovskii to explain the fractional nature of atomic magnetic moments of ferromagnets in alloys and pure metals.

Ferromagnetic semiconductors—ferrites—are considered separately; their study is of enormous interest for practice and for theory. Vonsovskii and Agafonova have given a polar-exciton theory of ferromagnetic semiconductors, which makes it possible to explain a number of their properties and to predict a number of new ones, for example, the existence, for some semiconductors, of a second Curie point in the region of absolute zero. The author shows the incorrectness of Néel’s theory, which regards a ferrite as an aggregate of sublattices of atoms of one kind.

Considerable space is devoted to the consideration of ferromagnetic alloys, in particular ordering alloys, as well as antiferromagnetism and metamagnetism.

The author then proceeds to consider the theory of the technical magnetization curve. This theory was created mainly by the work of the Soviet physicists N. S. Akulov, E. I. Kondorskii, and others. On its basis magnetostriction and other effects are considered.

Then in the reviewed book the further development of Akulov’s ideas on a quantum-mechanical basis is considered, carried out both by the author himself and by other magnetologists. In this field there are a number of successes, although the theory is far from complete. The book presents the results of a number of experimental works carried out on the basis of Akulov’s theory and in good agreement with its conclusions. Especially important are the works on determining anisotropy constants and their temperature dependence.

Further on, the regions of spontaneous magnetization, the Akulov–Bitter figure method, the works of Landau and Lifshitz, and others are examined in detail. The theory of small, ultimately single-domain particles, given by E. I. Kondorskii, is considered, and is fundamental for the development of modern magnetodielectrics and finely dispersed magnetically hard materials (metal-ceramic materials). Much space is devoted to the discussion of experiments on the detection of regions of spontaneous magnetization and to the theoretical interpretation of these experiments.

On the following pages of the book, the processes of changes in magnetization, reversible and irreversible displacement of boundaries, and rotation are examined in great detail. The theory of displacement processes was developed chiefly in the works of E. I. Kondorskii, and that of rotation processes in the works of N. S. Akulov. N. S. Akulov’s law of approach to saturation and a number of works on its experimental study are considered.

The various types of hysteresis, E. I. Kondorskii’s theory, and numerous works by both Soviet and foreign magnetologists on this question are examined in detail. Questions concerning the nature of the high coercive force of certain magnetically hard materials are discussed. One remark should be made here. In our literature the generally accepted terms are “Stoletov curves” for expressing the dependence of permeability or susceptibility on the field. This term is often used to denote the entire magnetization curve. The very initial section of this curve, lying in the region of very weak fields, is called the Rayleigh region. But since the theory of rotation processes was developed by N. S. Akulov, and the processes of boundary displacement were studied in the greatest detail by E. I. Kondorskii, it would be quite fair to call these sections of the magnetization curve the Akulov region and the Kondorskii region.

In the next, fifteenth, paragraph of the book, the properties of magnetic materials and certain methods of their treatment are considered. In the preceding paragraphs it was shown that high properties of magnetic materials can be obtained only if the requirements of the theory are fulfilled with respect to the purity of the materials, the presence or absence of internal stresses, etc. In the paragraph under consideration all the principal magnetic materials are described, and some of them (metal-ceramic) are described in the monographic literature for the first time. Many data are cited from experimental works by various authors on determining the dependence of various properties of materials on composition, heat treatment, and other factors. The influence of heat treatment, which plays the principal role in obtaining high properties of materials, is examined especially thoroughly. The principal data on the properties of ferrites are presented.

In the sixteenth paragraph, ferromagnetics in alternating fields and time effects (magnetic viscosity) are considered. Until now, in our monographic literature this section has been presented quite unsatisfactorily. In the book under review this gap is filled to a considerable extent. First, the dispersion of magnetic permeability is considered on the basis of the theory of V. K. Arkad’ev and the later work of Landau and Lifshitz. The theory of ferromagnetic resonance is examined, and data are given from a number of authors who investigated it. These results are discussed on the basis of modern theory.

Works on magnetic viscosity in aperiodic fields have until now received little coverage in the monographic literature, despite the great importance of this phenomenon for pulsed and a number of other processes. The works of Soviet scientists, to whom the principal experimental studies on the investigation of magnetic viscosity belong, have received especially little coverage. In the book under review, most of these works are considered.

Section 17 examines the connection between spontaneous magnetization and nonmagnetic and other properties of ferromagnets: heat capacity, magnetostriction, galvanomagnetic, thermomagnetic, and other effects. The most important phenomenon—magnetostriction, studied most fully by N. S. Akulov and his collaborators—is considered in great detail. These phenomena obey Akulov’s theory of even effects. The phenomena of changes in true magnetization (the paraprocess), studied by K. P. Belov, are compared with interesting experimental and theoretical results. The quantum theory of magneto-optical phenomena, developed by Vonsovskii and Sokolov, is presented.

The general impression made by S. V. Vonsovskii’s book is very good. Soviet physicists have received a substantial monograph written by a major specialist. The book is presented well and is quite accessible even to the nonspecialist magnetologist. The role of Russian and Soviet scientists is treated sufficiently fully.

Among the shortcomings of the book one should note the absence of discussion of certain questions which, although the present book was not intended to be an encyclopedia of magnetism, nevertheless ought to have been included. Such questions include the magnetic surface effect when a magnetic field changes, and the influence of eddy currents on the process of changes in magnetization. Without taking these factors into account, one cannot consider time-dependent processes in ferromagnetic conductors. The theory of these phenomena has been developed in detail by V. K. Arkad’ev, B. A. Vvedenskii, A. N. Tikhonov, and A. A. Samarskii.

Certain technical shortcomings must be attributed to the publisher and the printing house. The book was issued without a binding; such a manual, which all magnetologists will use daily, should have been brought out in a good binding. There are a number of misprints: thus, on p. 350, in the text, the coercive force of the silmanal alloy is correctly given as 5500 oersteds, while in the table on the same page it is equal to 550 oersteds. A very important table of the properties of magnetically soft materials on pp. 324, 325, occupying two pages, through the fault of the printing house was printed in such a way that its right half is shifted relative to the left by one line, which makes it difficult to use.

All this, of course, does not diminish the value of the book, whose appearance should be welcomed.

R. V. Telesnin