Summary For many years scientists have considered the rare earth elements as a group of nearly identical elements, and if something was known about one of them it was generally assumed to be the same for all of them. As rare earth scientists continue to work on these metals more exceptions are found each day. Indeed the differences in many cases are greater than those found for elements which lie in the same group, e.g. the alkaline earth metals, or the noble metals - Cu, Ag and Au. The differences due to the divalency of Eu and Yb as compared to the normal trivalent rare earth metals are the most obvious in consideration not only of their physical properties, but also in the method of preparing the pure metals. For the trivalent rare earths there are four major methods used to prepare these 14 metals (sections 1.1.1 to 1.1.3 and 1.2), and within each group there are minor but significant differences. A comparison of the basic physical properties shows significant and widely varying behaviors in their crystal structures (fcc→dhcp→Sm-type→hcp), melting points, (a difference of a factor of two between Ce and Lu), boiling points (the “saw-tooth” characteristic so vividly displayed in fig. 2.10), and vapor pressures (a difference of a factor of one million in the vapor pressures of La and Tm at 1300°C). Even the smooth, regular and systematic variation as implied in the term “lanthanide contraction” is not found in the metallic radii which exhibit anomalies at La, Gd and Lu, and between the light and heavy lanthanides (fig. 2.7a). Although, as noted, wide differences exist in the properties between certain rare earth elements, the systematic variation from one neighboring rare earth to the next (especially for the lanthanides) does occur, and allows one to predict properties which have not been determined experimentally. In making these predictions one should be aware that anomalies can occur and exercise caution. In so doing the application of systematics to rare earth materials can be a powerful tool for understanding their nature and predicting their behaviors in new surroundings.

Chapter 2 Preparation and basic properties of the rare earth metals

Publisher Summary This chapter reviews a reasonable accounting of the magnetic and transport properties of rare earth metals and their alloys The rare earths, or lanthanides, are the trivalent 4f shell transition metals Their magnetic properties stem from unpaired electrons in the 4f shell 4f electron wave functions are confined close to the nucleus and that wave function overlap with neighboring atoms in a lattice is vanishingly small To account for the observed magnetic order in the rare earths, an indirect exchange mechanism via three 5d–6s conduction electrons is invoked Strong evidence to support this view comes from the observed spin polarization of the conduction electrons A wide variety of magnetic structures are displayed by the rare earth metals and their alloys These range from simple ferromagnetism to complex sinusoidal or helical ordering; the magnetic structure sometimes involves sublattices Because of the low magnetic moments of the light rare earths it is possible for electric crystal field effects to dominate the magnetic exchange interaction

Chapter 3 Rare earth metals and alloys

J. P. Maita

Papers

ELECTRONIC PROPERTIES OF TWO NEW ELEMENTAL FERROMAGNETS: fcc Pr AND Nd.

Electronic transitions in near-equiatomic vanadium-ruthenium alloys