Gd substitution effect on the magnetocaloric properties of single-crystalline EuS

Abstract Europium monosulfide (EuS), which undegoes a ferromagnetic transition at T C = 18.2 K, is known as a potential candidate for magnetic refrigeration materials for hydrogen liquefaction because it exhibits a large magnetocaloric effect (MCE) near the boiling temperature of hydrogen (20.3 K). In this study, we synthesized a Gd-substituted EuS single crystal using the Bridgman method to explore a magnetic refrigeration material with a large MCE at temperatures above 20 K. The magnetization of the Gd-substituted EuS showed a steep increase below 30 K, indicating that T C is increased by the Gd substitution. However, the temperature dependence of the magnetic entropy change − ΔS m shows a broad peak centered at 20 K and a small shoulder structure at around 30 K. These results suggest that the Gd ions are not homogeneously substituted and that regions with higher Gd concentration enhance − ΔS m at around 30 K.