The valence state of Yb in YbXCu4(X=Al, Ag and Ga) compounds

Abstract

New ternary compounds of the type YbXCu4, where X=Al, Ag and Ga, have been prepared. The compounds with X=Al and X=Ga are found to have the hexagonal CaCu5-type structure while the compound with X=Ag has the cubic MgSnCu4-type structure. Magnetic susceptibility measurements reveal that Yb is in a nearly trivalent state in YbAlCu4, but in a divalent state in YbGaCu4. The susceptibility of YbAgCu4 shows a broad maximum at around 33 K, but follows a Curie-Weiss behaviour at high temperatures with an effective moment close to that of Yb3+. Thus both the structure type and the valence state of Yb appear to be strongly influenced by the nature of the X atom in YbXCu4 compounds.