Thermal and electrical conductivity of magnetic refrigerant RT2 Laves compounds (R: Rare earth; T: Al, Ni) for magnetic refrigerator application

Intermetallic Laves compounds with stoichiometry RT2 where R is a rare-earth metal and T is either Ni or Al are promising refrigerants in magnetic cooling refrigeration systems. These show a large magneto-caloric effect because of a second-order magnetic phase transition from a paramagnetic to a ferromagnetic state and have tunable transition temperature Tc between 20 and 77 K. In the present work, the thermal and electrical con-ductivity of RT2 polycrystals (R: Er, Gd, Dy, T: Ni, Al) in magnetic fields were reported from magnetic refrigeration point of view. It was found that the thermal conductivities of ErAl2, DyAl2, and DyNi2 at 0 T were in good agreement with reported literature data. All the studied RT2 compounds had small magnetic field dependence within 10% up to 5 T. In electric resistivity measurements, a characteristic kink was observed at T-c in zero fields for each of the compounds studied, and this kink was suppressed by a 5 T magnetic field. These data were used to evaluate the transport properties of RT2 compounds. Evaluation of thermal diffusion coefficient and eddy current power dissipation showed that an RT2 particle of submillimeter size has good heat transfer and negligible eddy current power dissipation, on the order of 10-12 W, in practical magnetic refrigeration cycles. These results show that RT(2 )compounds are excellent magnetic refrigerants for use in hydrogen liquefaction.