Giant magnetic refrigerant capacity in Ho3Al2 compound

Magnetic properties and magnetocaloric effects (MCEs) of the intermetallic Ho3Al2 compound are investigated by magnetization and heat capacity measurements. Two successive magnetic transitions, a spin-reorientation (SR) transition at TSR=31 K followed by a ferromagnetic (FM) to paramagnetic (PM) transition at TC=40 K, are observed. Both magnetic transitions contribute to the MCE and result in a large magnetic entropy change (ΔSM) in a wide temperature range. The maximum values of −ΔSM and adiabatic temperature change (ΔTad) reach 18.7 J/kg K and 4.8 K for the field changes of 0–5 T, respectively. In particular, a giant value of refrigerant capacity (RC) is estimated to be 704 J/kg for a field change of 5 T, which is much higher than those of many potential refrigerant materials with similar transition temperatures.

► Two successive magnetic transitions are observed in the Ho3Al2 compound.
► Both magnetic transitions contribute to MCE and result in a large ΔSM value.
► A giant value of RC is obtained to be 704 J/kg without hysteresis loss.
► The high RC value is caused by the overlap of the successive magnetic transitions.