Magnetically Ordered Crystals Containing Impurities
Авторы: Yu.A. Izyumov, M.V. Medvedev
Информация о издательстве: New York: Consultants Bureau, 1973. – 168 pp.,
The magnetic properties of alloys have been exploited in many technical applications for a long time. They have been the subject of numerous experimental investigations. However, deep theoretical studies of the magnetic properties of alloys commenced relatively recently because of considerable mathematical difficulties, some of which have not yet been overcome.
Two aspects of the theory of magnetic properties of alloys can be isolated. One is concerned with the origin and properties of the localized magnetic moments of the atoms in an alloy and with the interactions between them resulting in certain types of magnetic ordering. The other aspect is concerned with the magnetic ordering and the resultant magnetic properties of an alloy. The first aspect is closely related to the electron properties of an alloy and is usually considered within the band theory of metals. The second aspect involves the use of specified values of atomic magnetic moments and of the exchange interactions between them, which are frequently considered in the Heisenberg model of a magnetic crystal. The problem of the applicability of the Heisenberg model to a metal must be resolved by bearing in mind its magnetic properties. It is found that the Heisenberg model often provides a satisfactory description of magnetic structures and of the spectra of magnetic excitations.
The present monograph deals with the second aspect. The adoption of the Heisenberg model makes it possible to apply the theory associated with it not only to alloys but even to a greater extent to nonmetallic compounds. Our monograph is concerned with the magnetic properties of ferromagnetic crystals consisting of two types of magnetic atom, mixed in a random manner, i.e., it will be assumed that there is no atomic ordering in a crystal with impurities. Much of the book is concerned with dilute systems, in which the concentration of the second component is so low that its atoms can be regarded as isolated from one another. We shall begin by solving the properties of a crystal containing a single impurity atom and then we shall go over easily to the properties of a crystal with a finite but low impurity concentration.