Low-Temperature Specific Heats of RECu6-Type Compounds

We measured specific heats of RECu 6 -type magnetic compounds (RE=Nd, Sm and Pr) at 0.1<T<40 K. The results show successive magnetic phase transitions in zero magnetic field for NdCu 6 at T=5.66, 5.78, 5.93 and 6.02 K and for SmCu 6 at T=5.6 and 9.4 K. From the magnetic specific heat of PrCu 6 , we propose an energy scheme of 4f levels of the Pr ion under the influences of the crystalline electric field.