This is a textbook of what is often called magnetochemistry. We take the
point of view that magnetic phenomena are interesting because of what
they tell us about chemical systems. Yet, we believe it is no longer
tenable to write only about such subjects as distinguishing
stereochemistry from the measurement of a magnetic susceptibility over a
restricted temper- ature region; that is, paramagnetism is so
well-understood that little remains to explore which is of fundamental
interest. The major purpose of this book is to direct chemists to some
of the recent work of physicists, and in particular to a lengthy
exposition of magnetic ordering phenomena. Chemists have long been
interested in magnetic interactions in clusters, but many have shied
away from long-range ordering phenomena. Now however more people are
investigating magnetic behavior at temperatures in the liquid helium
region, where ordering phenomena can scarcely be avoided. The emphasis
is on complexes of the iron-series ions, for this is where most of the
recent work, both experimental and theoretical, has been done. The
discussion therefore is limited to insulating crystals; the nature of
magnetism in metals and such materials as semiconductors is sufficiently
different that a discussion of these substances is beyond our purposes.
The book is directed more at the practical experimentalist than at the
theoretician.