The rare earths have a unique place among the elements. Although very much alike chemically and in most phy~ical properties they each have very different and striking magnetic properties. The reason, of course, lies in their 4f electrons which determine the magnetic properties but have little effect on other chemical and physical behaviour. Although they are not rare, some indeed are among the more common heavy elements in the earth's crust, the difficulty of separation has meant that their intricate magnetic properties have only recently been unravelled. Now, however, the general pattern of their magnetism is well charted and the underlying theory is well understood. Both are thoroughly summarised in this book. It provides an excellent example of the kind of extensive synthesis which is possible with modem solid state physics. it represents only a high plateau in the ascent to complete understanding. But It will become clear to the reader that while the overall position is satisfactory there are many details still to be elucidated experimentally and much to be done theoretically before all the underlying forces are identified and estimated from a priori calculations. It is hoped that the book will provide a useful stimulus in this direction. It should also be of use to those who are interested in related disciplines, for example the rare earth compounds, or the transition metals. In addition rare earths promise to be important technologically as alloy constituents.

Science and Technology of Rare Earth Materials reviews the important aspects of the science and technology of rare earth materials, covering the entire spectrum from occurrence to extraction and purification, phase relationships, electronic structure, and applications. This book is organized into five sections encompassing 19 chapters. The occurrence, extraction, and production of rare earths are discussed in the first section, followed by purification methods employed for rare earths, together with the role of impurities on their behavior. The phase relations among the rare earth alloys, including a particular reference to the technologically important rare earth-cobalt alloys, and phase relations among the rare earth oxides are considered in the second section. The succeeding two sections focus on studies of the electronic structure of rare earth materials, with emphasis on the use of nuclear magnetic resonance and Mössbauer spectroscopy. Theoretical conceptions are set forth as well as the effect of crystal fields and valence fluctuations on the properties of rare earth systems. The final section describes some of the extensive current uses of rare earth materials such as in the steel industry and in permanent magnets, as well as emerging applications in catalysis, hydrogen storage, ferroelectrics, and fast ion conductors. This book is a valuable resource for researchers and students interested in rare earths.

This monograph presents a unified and coherent account of an important, focused area of rare-earth magnetism -- magnetic structures and excitations -- which both reflects the nature of the fundamental magnetic interactions and determines many of the characteristic properties of metals. The authors concentrate on the essential principles and their applications to typical examples, generally restricting the discussion to the pure elements and considering alloys and compounds only when they are instructive in illuminating particular topics. Both authors have been involved for some time in the effort that has been made in Denmark to study, both theoretically and experimentally, the magnetic structures and especially the excitations in the rare earths. This account of the subject represents the result of their experience, and it has been written in the hope that it will be useful not only to those who have a special interest in rare-earth magnetism, but also to a wider audience of physicists and condensed matter scientists interested in the techniques and achievements of modern research in magnetism.