Large magnetocaloric effects controlled by hydrogenation and partial substitution in itinerant-electron metamagnetic La(Fe_xSi_(1-x))_(13) compounds

摘要

Magnetic refrigerations promise great advantages such as high environmental safety related so dispensation with ozone depleting gases as well as high energy efficiency. Magnetic materials having the large magnetocaloic effects (MCEs) such as the isothermal magnetic entropy change DELTAS_m and the adiabatic lemperature change DELTA T_(ad) are utilized as magnetic refrigerants to realize a magnetic refrigerator Recently, we have developed La(Fe_xSi_(1-x))_(13) (0.86<=x<=0.90) compounds as promising magnetic refrigerants, under favor of appearance of the itinerant-electron metamagnetic (IEM) transition, namely, the first-order phase transition from the paramagnetic (P) state to the ferromagnetic (F) state in applied magnetic fields. These compounds exhibit large values of DELTA S_m and DELTA T_(ad) in the vicinity of the Curie temperature T_c approx 190 K. For practical applications to magnetic refrigerations, the spread of a working temperature range is required. That is, the increase of T_c is necessary for room temperature cooling. On the contrary, the decrease of T_c comes through the utilizations of new devices such as high-T_c superconductor filters for mobile electronic communications. In the present study, to obtain high-performance magnetic refrigerants, the control of T_c and MCEs by hydrogenation and partial substitution has been investigated.