Large reversible magnetocaloric effect due to a rather unstable antiferromagnetic ground state in Er4NiCd

Abstract

Er 4 NiCd crystallizes with the Gd4RhIn type structure, space group F4¯3m, a=1333.3 pm. The nickel atoms have trigonal prismatic rare earth coordination. Condensation of the NiEr6 prisms leads to a three-dimensional network which leaves voids that are filled by regular Cd4 tetrahedra. Er4NiCd shows Curie–Weiss behavior above 50 K with TN=5.9 K. At field strength of 4 kOe a metamagnetic step is visible, together with the positive paramagnetic Curie-temperature (7.5 K) indicative for the rather unstable antiferromagnetic ground state. Therefore, a large reversible magnetocaloric effect (MCE) near the ordering temperature occurs and the values of the maximum magnetic-entropy change −ΔSMmax reach 18.3 J kg−1 K−1 for the field change of 5 T with no obvious hysteresis loss around 17 K. The corresponding RCP of 595 J kg−1 is relatively high as compared to other MCE materials in that temperature range. These results indicate that Er4NiCd could be a promising system for magnetic refrigeration at temperatures below liquid H2.