Control of large magnetocaloric effects in metamagnetic [formula omitted] compounds by hydrogenation

Abstract

To obtain large magnetocaloric effects (MCEs) due to the itinerant-electron metamagnetic (IEM) transition in La ( Fe x Si 1 − x ) 13 , the Curie temperature T C has been controlled by hydrogen absorption. In La ( Fe 0.88 Si 0.12 ) 13 H y compounds, T C = 195 K for y = 0.0 increases with increasing hydrogen concentration, resulting in T C = 330 K for y = 1.6 . Furthermore, the magnetic moment is also stabilized against temperature by hydrogen absorption. Since the IEM transition is preserved after hydrogenation, large MCEs of the magnetic entropy change Δ S m and the adiabatic temperature change Δ T ad have been observed around room temperature. A large value of Δ T ad has been confirmed by a direct measurement in adiabatic magnetic field change for the La ( Fe 0.89 Si 0.11 ) 13 H y ( y = 0.0 and 1.6). Consequently, the La ( Fe x Si 1 − x ) 13 compounds and their hydrides are promising as high-performance magnetic refrigerants working in a wide range of temperature covering room temperature in relatively low applying magnetic fields.