Giant Magnetic Entropy Change in Hydrogenated La(Fe_0.88Si_0.12)₁₃H_y Compounds

Abstract

A magnetic entropy change ΔS_M due to the itinerant-electron metamagnetic (IEM) transition was estimated to be −23 J/kg K around the Curie temperature for La(Fe_0.88Si_0.12)₁₃ in the magnetic field change from 0 to 5 T. In order to control the Curie temperature while keeping such a large value of ΔS_M, hydrogen absorption was carried out. La(Fe_0.88Si_0.12)₁₃H_1.0 with T_C=274 K shows a large ΔS_M due to the IEM transition around room temperature. The adiabatic temperature change ΔT_ad from 0 to 2 T is about 7 K, comparable to that of Gd₅(Ge_0.5Si_0.5)₄. By changing the hydrogen concentration, the Curie temperature can be controlled from 195 to 336 K. It should be noted that the magnitude of ΔS_M is almost the same after hydrogen absorption. Therefore, the hydrogenated La(Fe_0.88Si_0.12)₁₃H_y compounds are promising magnetic refrigerants working in a wide range of temperature.