Heterogeneous GdTbDyCoAl high-entropy alloy with distinctive magnetocaloric effect induced by hydrogenation

Abstract

Developing novel magnetocaloric materials is of great significance for the applications of magnetic refrigeration. In this study, we designed a heterogeneous rare-earth-based high-entropy alloy (HEA) comprising amorphous matrix, local crystal-like cluster and nanocrystalline dihydride with average size of 7.5 nm through isothermal hydrogenation. This heterogeneous structure can significantly tune the magnetocaloric effect of alloy. After hydrogenation, the predominant exchange interaction transforms from ferromagnetic to antiferromagnetic with the disappearance of spin-glass-like behavior, and a complete second-order magnetic transition is obtained. Compared with the Gd 20 Tb 18 Dy 18 Co 20 Al 24 high-entropy metallic glass with a small number of nanocrystals, the maximum magnetic entropy change of the hydrogen-containing HEA is increased from 8.8 to 13.6 J kg −1 K −1 under applied magnetic field change of 5 T accompanying unobvious hysteresis and decreased magnetic transition temperature from 59 to 8 K, which is more promising as magnetic refrigerant at cryogenic temperature. This work provides a novel concept of designing heterogeneous structure in terms of special cluster and preferential nanocrystalline to modulate the properties of metallic glasses. • Heterogeneous GdTbDyCoAlH high-entropy alloy was obtained by isothermal hydrogenation. • The heterogeneous structure is composed of amorphous matrix, crystal-like cluster and nanocrystalline dihydride. • The maximum magnetic entropy change increases from 8.8 to 13.6 J kg −1 K −1 after hydrogenation. • The cryogenic magnetism is tuned from ferromagnetic to antiferromagnetic after hydrogenation.