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 RB2 compounds conform with the size rule which had been established in the mid 1930s. Electron concentration effects have also been observed in the RB2 phases. A number of anomalies and unusual behaviors have been discovered over the years: the La deficiency in "LaNi2" and of R in other "RNi2" Laves phase compounds; the crystal structure sequence in the RMn2 compound series; the relationship between the Debye temperature and the radius ratio; the Ce valence in the CeB2 compounds; and the thermodynamic nature of the magnetic transition in the RCo2 phases.