Control of Working Temperature of Isothermal Magnetic Entropy Change in La_0.8Nd_0.2(Fe_0.88Si_0.12)₁₃by Hydrogen Absorption for Magnetic Refrigerants

$La_1-zNd_z(Fe_0.88Si_0.12)₁₃$ and their hydrides were investigated to obtain large magnetocaloric effects (MCEs) in a wide temperature range, including room temperature, for applications in magnetic refrigents. Since the magnetization change due to the itinerant-electron metamagentic (IEM) transition for $La_1-zNd_z(Fe_0.88Si_0.12)₁₃$ becomes larger with increasing z, the isothermal magnetic entropy change ${\Delta}S_m$ and the relative cooling power (RCP) are enhanced. In addition, the Curie temperatrue $T_C$ of $La_0.8Nd_0.2(Fe_0.88Si_0.12)₁₃$ is increased from 193 to 319 K by hydrogen absorption, with the IEM transition. The maximum value of $-{\Delta}S_m$, $-{\Delta}S{_m}^max$, in a magnetic field change of 2 T for $La_0.8Nd_0.2(Fe_0.88Si_0.12)₁₃H_1.1$ is about 23 J/kg K at $T_C$ = 288 K, which is larger than that of 19 J/kg K at $T_C$ = 276 K for $La(Fe_0.88Si_0.12)₁₃H_1.0$. The value of RCP = 179 J/kg of the former is also larger than 160 J/kg of the latter. It is concluded that the partial substitution of Nd improves MCEs in a wide temperautre range, including room temperature.