Publisher Summary This chapter discusses the properties of the rare earth hydrides in terms of ionic bonding rather than band structure. The bonding in Eu and Yb hydrides is decidedly more ionic; they resemble the alkaline earth hydrides in most of their properties. This is attributed to the stability of the underlying 4f states because they are fully occupied in the case of Yb and half-occupied (one electron in each orbital according to Hund's rule) in the case of Eu. The properties and characteristics of the rare earth hydrides have been extensively reviewed in the past by Bos and Gayer and Mueller, and the information has been updated by Libowitz. Consequently, emphasis will be placed on work published subsequent to those dates. The chapter summarizes the magnetic properties of the rare earth hydrides and then compares them with the properties of the rare earth metals. The decrease in magnetic susceptibility of the metal on hydride formation, which is characteristic of most transition metal hydrides, occurs only in the heavier rare earth metals (Gd to Tm) including yttrium. The lighter rare earths Ce, Pr, Nd, and Sm show essentially no change in magnetic susceptibility on hydride formation.

J.B. Lightstone

Papers

Point defects in some rare earth dihydrides.