Magnetocaloric effect and refrigerant capacity in Sr-doped Eu8Ga16Ge30 type-I clathrates.

Magnetic properties, the magnetocaloric effect (MCE) and refrigerant capacity (RC) were investigated in Eu8Sr8-xGa16Ge30 (x=0,4) type-I clathrates. The substitution of Sr for Eu decreases the Curie temperature (TC) and saturation magnetization (MS) from 35 K and 65 emu/g for the x =0 composition to 15 K and 35 emu/g for the x=4 composition. This is attributed to the increase in the Eu-Eu distance with Sr substitution. The large MCE and RC are achieved in both specimens. For a field change of 3 T, the MCE and RC reach the largest values of 5.8 J /kg K and 127.6 J/kg for x=0 composition and 4.3 J /kg K and 72.1 J/kg for x=4 composition. The broadening of the MCE curves is likely associated with the ordering of the magnetic moments of Eu that occurs below 10 K. The large values of MCE and RC, in addition to the absence of thermal and field hysteresis indicate that these clathrate materials are very interesting for cryogenic magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]