Enhanced low-field magnetocaloric effect in Dy-doped hexagonal GdBO₃ compounds

Borates have attained increasing attention attributed to their excellent thermal stability, distinctive thermodynamic property, and high mechanical strength in recent years. A series of polycrystalline Dy-doped GdBO₃ compounds was prepared, their crystal structures, magnetic properties, and cryogenic magnetocaloric effects were comprehensively investigated. The compounds crystallize in hexagonal structure (space group P6₃/mmc), the lattice constant decreases with the increase of Dy content. Dy-doping in GdBO₃ significantly reduces critical magnetic field and enhances low-field magnetocaloric effect. The maximum magnetic entropy changes for the Gd_1–xDy_xBO₃ (x = 0.6, 0.8, and 1) compounds in a field change of 2 T surpass 17.3 J/(kg·K) at 2.5 K, enhanced by nearly 120% compared to GdBO₃ (8.0 J/(kg·K)). Besides, the corresponding refrigeration capacity increases from 33.9 to 62.2, 57.2, and 72.5 J/kg, respectively, with an enhancement of 70%–110%. The considerable maximum magnetic entropy change, refrigerating capacity, and temperature averaged entropy change make them competitive candidates for cryogenic magnetic refrigeration.