Table-like magnetocaloric effect and enhanced refrigerant capacity in Eu8Ga16Ge30-EuO composite materials

A large reversible magnetocaloric effect (MCE) and enhanced refrigerant capacity (RC) were observed in multiphase composite materials composed of type-I clathrate Eu8Ga16Ge30 and EuO. Eu8Ga16Ge30 undergoes two successive ferromagnetic transitions at 10K and 35 K, and EuO exhibits a ferromagnetic transition at 75 K. A large RC of 794 J/kg for a field change of 5 T over a temperature interval of 70K was achieved in the Eu8Ga16Ge30-EuO composite with a 40%-60% weight ratio. This is the largest value ever achieved among existing magnetocaloric materials for magnetic refrigeration in the temperature range 10 K-100 K. Adjusting the Eu8Ga16Ge30 to EuO ratio is shown to produce composites with table-like MCE, desirable for ideal Ericsson-cycle magnetic refrigeration. The excellent magnetocaloric properties of these Eu8Ga16Ge30-EuO composites make them attractive for active magnetic refrigeration in the liquid nitrogen temperature range. (C) 2011 American Institute of Physics. [doi:10.1063/1.3654157]