Long-range ferromagnetism and giant magnetocaloric effect in type VIII Eu8Ga16Ge30 clathrates

Abstract

Long-range ferromagnetism and low-field giant magnetocaloric effect are observed in Eu8Ga16Ge30 with the type VIII clathrate crystal structure, a material that is better known for its thermoelectric properties. Magnetization and modified Arrott plots indicate that the system undergoes a second-order ferromagnetic-paramagnetic phase transition at ∼13K. The low-field giant magnetic entropy change (−ΔSM∼11.4J∕kgK for Δμ0H=3T) coupled with the absence of thermal hysteresis and field hysteresis makes the system very attractive for low temperature magnetic refrigeration. The giant magnetic entropy change originates from the large magnetization (7.97μB per Eu ion) and the sharp change with temperature at the paramagnetic-ferromagnetic transition.