A novel low temperature rearrangement of atoms in the rare earth intermetallic compound ErFe₃

The Mossbauer effect in 57 Fe has been used to locate and identify a novel low temperature rearrangement of atoms in the rare earth intermetallic compound ErFe 3 . It is argued that the iron atoms at both the c and h crystallographic sites suddenly shift their positions as the temperature is lowered through 47+or-1K. However, the movements of these iron atoms do not give rise to a change in the space group R3m of the crystal. Some suggestions are made concerning the driving force behind the transition.