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

$Er4NiCd$ crystallizes with the $Gd4RhIn$ type structure, space group $F4¯3m$⁠, $a=1333.3pm$⁠. 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 $TN=5.9K$⁠. 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 $18.3Jkg−1K−1$ for the field change of 5 T with no obvious hysteresis loss around 17 K. The corresponding RCP of $595Jkg−1$ 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 $H2$⁠.