Giant reversible magnetocaloric effect in antiferromagnetic GdCo ₂B₂ compound

The magnetocaloric effect of GdCo₂B₂ was studied by magnetization and heat capacity measurements. A giant reversible magnetocaloric effect has been observed which is related to a field-induced first order metamagnetic transition from antiferromagnetic to ferromagnetic state. The values of maximum magnetic entropy change (-Δ SM max) reach 9.3 and 21.5 J kg_-1 K_-1 for the field change of 2 and 7 T with no obvious hysteresis loss around 25 K, respectively. The corresponding maximum adiabatic temperature changes (Δ T ad max) are evaluated to be 6.7 and 18.9 K. These values are even larger than some of potential magnetic refrigerant materials reported in the same temperature range and also comparable to the room temperature giant magnetocaloric materials. These results indicated that GdCo₂B₂ could be a promising candidate for magnetic refrigeration at low temperatures.