Multiple transitions and wide refrigeration temperature range in R₃NiSi₂ (R = Tb, Dy) compounds

In this work, orthorhombic polycrystalline Tb₃NiSi₂ and Dy₃NiSi₂ compounds were prepared and magnetocaloric effect during multiple magnetic transitions was investigated in detail. Tb₃NiSi₂ compound displays four different magnetic transitions at 94 K, 115 K, 134.2 K, and 140.6 K, respectively. The maximal value of magnetic entropy change are about 4.5 J/kg K and 11.1 J/kg K at 141 K for Tb₃NiSi₂ compound under a field change of 0–2 T and 0–7 T, respectively. For the Dy₃NiSi₂ compound, three obvious magnetic transitions are found at 29.3 K, 65.4 K, and 76.6 K and the maximal value of magnetocaloric effect are about 3.6 J/kg K and 10.8 J/kg K at 77 K for a field change of 0–2 T and 0–7 T, respectively. Due to the multiple magnetic transitions, both compounds exhibit the wide refrigeration temperature range and considerable refrigerant capacity. The results reveal that the value of refrigeration temperature range and refrigerant capacity are 66.9 K and 549.1 J/kg for Tb₃NiSi₂ compound, and 64.0 K and 489.6 J/kg for Dy₃NiSi₂ compound, respectively. Therefore, R₃NiSi₂-family compounds have a potential application in middle temperature magnetic refrigeration.