Multiple Magnetic Phase Transitions and Giant Refrigerant Capacity in a GdDyHoErTm High-Entropy Alloy.

Magnetocaloric high-entropy alloys (HEAs) have recently garnered significant interest owing to their potential applications in magnetic refrigeration, offering a wide working temperature range and large refrigerant capacity. In this study, we thoroughly investigated the structural, magnetic, and magnetocaloric properties of equiatomic GdDyHoErTm HEAs. The as-cast alloy exhibits a single hexagonal phase, a randomly distributed grain orientation, and complex magnetism. In particular, multiple magnetic phase transitions occur over a wide temperature range in this rare-earth HEA, which is attributed to the diverse magnetic properties of the constituent rare-earth elements. Accordingly, a table-like magnetocaloric effect (the maximum magnetic entropy change of 7.5 J/kg K at 5 T) is achieved in the temperature range of 27-175 K, leading to a giant refrigerant capacity of 923 J/kg and relative cooling power of 1110 J/kg. Our findings in the rare-earth HEAs with multiple magnetic phase transitions open up a pathway to further develop high-performance magnetocaloric materials in the field of cryogenic magnetic refrigeration.