Large reversible magnetocaloric effect in antiferromagnetic HoO powders.

Giant magnetocaloric materials are highly promising for technological applications in magnetic refrigeration. Although giant magnetocaloric effects were discovered in first-order magnetic transition materials, it is accompanied by some non-desirable drawbacks, such as important hysteretic phenomena, irreversibility of the effect, or poor mechanical stability, which limits their use in applications. Here, we report the discovery of a giant magnetocaloric effect in commercialized HoO oxide at low temperature (around 2 K) without hysteresis losses. HoO is found to exhibit a second-order antiferromagnetic transition with a Néel temperature of 2 K. At an applied magnetic field change of 5 T and below 3.5 K, the maximum value of magnetic entropy change [Formula: see text], the refrigerant capacity (RC) were found to be 31.9 J.K.kg and 180 J.K, respectively.