Influence of hydrogenation on volume dependence of the Curie temperature and entropy change in La(Fe_0.86Si_0.14)₁₃

To elucidate the influence of hydrogenation on the volume dependence of the Curie temperature T_C and the entropy change ΔS_m in La(Fe_0.86Si_0.14)₁₃, magnetic properties under hydrostatic pressure have been investigated. In the thermomagnetization curves of La(Fe_0.86Si_0.14)₁₃H_1.1, the first-order phase transition becomes clearer due to the decrease of volume, as observed before hydrogenation. By hydrogenation, the reduction of the pressure dependence of T_C by about 20% is caused by the magnetovolume contribution to the free energy. Meanwhile, the maximum value of ΔS _m is increased in magnitude from -9 to -18 J/kgK by applying pressure of 1 GPa. Accordingly, the decrease of volume is also effective to enhance ΔS_m after hydrogenation.