Anomalous Schottky Specific Heat and Structural Distortion in Ferromagnetic PrAl2

Unique from other rare earth dialuminides, PrAl2 undergoes a cubic to tetragonal distortion below T = 30 K in a zero magnetic field, but the system recovers its cubic symmetry upon the application of an external magnetic field of 10 kOe via a lifting of the 4f crystal field splitting. The nuclear Schottky specific heat in PrAl2 is anomalously high compared to that of pure Pr metal. First principles calculations reveal that the 4f crystal field splitting in the tetragonally distorted phase of PrAl2 underpins the observed unusual low temperature phenomena.