Large magnetocaloric effects in NaZn_(13)-type La(Fe_xSi_(1-x))_(13) compounds and their hydrides composed of icosahedral clusters

摘要

The magnetocaloric effects (MCEs) in cubic NaZn_(13)-type La(Fe_xSi_(1-x))_(13) compounds and their hydrides composed of icosahedral clusters have been investigated because these compounds exhibit the itinerant-electron metamagnetic (IEM) transition just above the Curie temperature T_C. The value of T_C can be increased continuously up to about 336 K by hydrogen absorption into the La(Fe_xSi_(1-x))_(13) compounds. Therefore, the values of the isothermal magnetic entropy change ΔS_m and the indirectly estimated adiabatic temperature change ΔT_(ad) due to the IEM transition become - 31 J/kg K and 15.4 K, respectively, in the magnetic field change from 0 to 5 T at T_C = 287 K for the La(Fe_xSi_(1-x))_(13)H_(1.1) compound. The MCEs in the compounds having the IEM transition are much larger than those in the compounds exhibiting the second-order magnetic transition at T_C. The direct measurement of the adiabatic temperature change ΔT_(ad)~d has confirmed such a large value. Consequently, the La(Fe_xSi_(1-x))_(13) compounds and their hydrides having the IEM transition are promising as high performance magnetic refrigerants working in a wide temperature range covering room temperature in relatively low magnetic fields.