This volume is part of is a continuous series of books covering all aspects of rare earth science, including chemistry, life sciences, materials science, and physics. The book's main emphasis is on rare earth elements [Sc, Y, and the lanthanides (La through Lu], but whenever relevant, information is also included on the closely related actinide elements. Individual chapters are comprehensive, broad, up-to-date, critical reviews written by highly experienced, invited experts. The series, which was started in 1978 by Professor Karl A. Gschneidner Jr., combines, and integrates, both the fundamentals and applications of these elements with two published volumes each year.