Large Reversible Magnetocaloric Effect Around Liquid Hydrogen Temperature in Er4PdMg Compound

The magnetic properties and the magnetocaloric effect (MCE) in the Er₄PdMg compound have been investigated by magnetization and heat capacity measurements. The compound undergoes a second-order magnetic phase transition from a paramagnetic to a ferromagnetic state at Curie temperatures of T_C ~ 21.5 K, which is just above the liquid hydrogen temperature (20.3 K). A large reversible MCE was observed. The maximum values of magnetic entropy change (-ΔS^max_M ) and adiabatic temperature change (ΔT^max_ad ) for Er₄PdMg under a field change of 0-7 T are 20.6 J/kg K and 5.5 K, respectively. The corresponding value of relative cooling power (RCP) was evaluated to be 742 J/kg. The large reversible MCE together with considerable RCP values makes the Er₄PdMg compound attractive for magnetic refrigeration.