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

•Multiple magnetic transitions are observed in R3NiSi2 (R = Tb, Dy) compounds.•Large refrigerant capacity and wide refrigeration temperature range are obtained.•Considerable magnetic entropy change is acquired for a field change of 0–7 T.•Comprehensive performance is good for the application in middle temperature region. 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 Tb3NiSi2compound 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.