Tunable magnetic and magnetocaloric properties by thermal annealing in ErCo2 atomized particles

Abstract

Processing magnetocaloric materials into magnetic refrigerants with appropriate shapes is essential for the development of magnetic refrigeration systems. In this context, the impact of processing on the physical properties of the materials is one of the important issues. Here, we investigate the crystallographic, magnetic, and magnetocaloric properties of gas-atomized particles of the intermetallic compound ErCo2, a giant magnetocaloric material for low-temperature applications. The results demonstrate that the physical properties of ErCo2 are significantly changed by atomization and subsequent thermal annealing. In the as-atomized particles, the magnetic transition temperature increases from 34 to 56 K, and the phase transition changes from first order to second order. The thermal annealing shifts the transition temperature back to the original one and restores the first-order phase transition characteristic. The changes in magnetic properties are closely related to those in crystallographic properties, suggesting the importance of the magneto-structural coupling. The magnetic entropy change −ΔSM of the particles can be tuned in size, shape, and peak temperature depending on the annealing conditions. The peak value of −ΔSM varies in the range of 9–33 J kg−1 K−1 for a field change of 0–5 T. All the ErCo2 atomized particles have magnetocaloric properties comparable or superior to other promising candidates for low-temperature magnetic refrigerants.