Spontaneous Volume Magnetostriction of RCo2 Compounds

The thermal expansion of RCo 2 compounds (R=Gd, Tb, Dy, Ho and Er) has been measured from 4.2 K up to 700 K. All the RCo 2 compounds show an Invar-like thermal expansion anomaly below their Curie temperatures: a large positive spontaneous volume magnetostriction was found. The large magneto-volume coupling is presumably of help towards a first order phase transition observed in DyCo 2 , HoCo 2 and ErCo 2 .