Large reversible magnetic entropy change of R3Ni6Al2 (R = Dy, Ho and Er) compounds

•Large low-temperature MCE was obtained in R3Ni6Al2 compounds.•Large refrigeration capacity in Dy3Ni6Al2 compound was observed.•The magnetic transitions were confirmed to be second order. Large magnetocaloric effect (MCE) and magnetic properties in R3Ni6Al2 (R = Dy, Ho and Er) compounds were systematically investigated. Large magnetic moment and low magnetic transition temperature play a decisive role in the magnetocaloric performance for R3Ni6Al2 (R = Dy, Ho and Er) compounds. Ho3Ni6Al2 compound shows the largest magnetic entropy change with the value of 19.7 J/kg K at ~20 K under field change of 0–5 T because of the large magnetic moment and moderate transition temperature. For Dy3Ni6Al2 compound, it exhibits the largest refrigeration capacity with the value of 394.5 J/kg due to the successive magnetic transitions. The Er3Ni6Al2 compound has a large MCE at ultra-low temperatures around 4 K. Furthermore, the second-order phase transition in R3Ni6Al2 (R = Dy, Ho, Er) compounds were confirmed according to Arrott plots, rescaled universal magnetic entropy change curves and mean field theory with negligible thermal and magnetic hysteresis. The large reversible MCE with low working temperatures indicates that R3Ni6Al2 compounds are potential excellent MCE materials for low-temperature magnetic refrigeration.