Trivalent rare earths in layered (LX)1.15NbX2 chalcogenides

The magnetic and electrical properties of the layered misfit compounds (LX)1.15NbX2 have been studied for the rare earths L=Ce, Sm, Gd, and Yb and the chalcogens X=S and Se, on single crystals grown by vapor transport. The compounds consist of double layers of LX, which are 111 rocksalt planes, inserted between layers of NbX2. In spite of the fact that the LX rocksalt compounds SmS, SmSe, and YbS contain divalent lanthanides at atmospheric pressure, in the misfit compounds the lanthanides are trivalent. This may be due to a preference for a 1 electron per rare earth charge transfer to the NbX2 layer.