Magnetic Characteristics of Hydrogenated Holmium

Abstract

Various physical and chemical properties of the lanthanide hydrides suggest that they are saline in nature, the hydrogen existing as a negatively charged ion. These properties further suggest that the anionic charge is obtained from the conduction band of the lanthanide and that in the fully hydrogenated metal the conduction band is completely depopulated. Since coupling of the lanthanides occurs via the conduction electrons, this should lead to very considerable suppression of the interactions in the hydrides compared to the element, but an unchanged effective atomic moment. To determine whether this is the case susceptibility measurements have been made on a series of nine Ho–H alloys. These show for the dihydride, which still contains some conduction electrons, a Néel point at around 8°K (instead of 135°K for the element), whereas for the trihydride, which lacks conduction electrons, no Néel point is observed down to 4°K. Susceptibilities of the hydrides above about 15°K obey the Curie-Weiss law with a much smaller Weiss constant than that for elemental holmium. The atomic moment is found, however, to be virtually unaffected by hydrogenation.