Giant magnetocaloric effect in clathrates

Abstract

We report an observation of large magnetocaloric effect in clathrate compounds. Systematic dc magnetization in polycrystalline Eu8Ga16Ge30 clathrates was studied in the temperature range of 5–60 K and over an applied field range of 0–3 T. Change in entropy (ΔSmag) was calculated using the Maxwell relation from the family of M-H curves at different temperatures in the vicinity of the ferromagnetic Curie temperatures. Large entropy changes of 6 and 9.3J∕kgK were observed for the type-I and type-VIII phases, respectively. The larger effect in type-VIII samples can be associated with the sharper ferromagnetic transition. Overall, these results indicate that the clathrates known to have potential for excellent thermoelectric properties are also promising candidates as magnetic refrigerant materials.