Control of magnetocaloric effects by hydrogen absorption into La(Fe _xSi_1-x)₁₃ magnetic refrigerants

The magnetocaloric effects (MCE's) due to the itinerant-electron metamagnetic (IEM) transition have been investigated for La(Fe _xSi_1-x)₁₃H_y compounds. By controlling the hydrogen concentration y, the Curie temperature T_C was elevated from around 180 K to room temperature with retaining the IEM transition. A large magnetic entropy change ΔS_m was confirmed in x = 0.88 even in relatively small magnetic field and ΔS_m is enhanced by increasing Fe concentration up to x = 0.90, consistent with the theoretical predictions. The value of ΔS_m is still large enough after increasing TC by hydrogen absorption into La(Fe_xSi _1-x)₁₃H_y compounds. In these compounds and hydrides, the value of the adiabatic temperature change ΔT_ad estimated from the specific heat data was also confirmed to be large. Furthermore, directly measured adiabatic temperature change ΔT _ad^d almost accords with ΔT_ad, both in magnitude and thermal variation. In addition, La(Fe_xSi _1-x)₁₃H_y, compounds have excellent thermal transport properties. Consequently, the present compounds are one of the promising candidates for magnetic refrigerants working at wide temperature ranges covering room temperature.