Binary rare earth Laves phases — an overview

The rare earth metals form the largest subset of the AB 2 Laves phase compounds. The rare earth element ( R ) is always the larger A metal, and they form Laves phases with most of the Group 7–10 elements, plus Mg and Al. As with all Laves phases, the rare earth RB 2 compounds conform with the size rule which had been established in the mid 1930s. Electron concentration effects have also been observed in the RB 2 phases. A number of anomalies and unusual behaviors have been discovered over the years: the La deficiency in “LaNi 2 ” and of R in other “ R Ni 2 ” Laves phase compounds; the crystal structure sequence in the R Mn 2 compound series; the relationship between the Debye temperature and the radius ratio; the Ce valence in the Ce B 2 compounds; and the thermodynamic nature of the magnetic transition in the R Co 2 phases.