ADVANTAGE OF THE ITINERANT ELECTRON METAMAGNETIC TRANSITION IN La(Fe_xSi_(1-x)_(13) FOR HIGH PERFORMANCE MAGNETIC REFRIGERATION

摘要

Advantage of the itinerant electron metamagnetic transition in La(Fe_xSi_(1-x))_(13) for magnetic refrigerants is discussed in terms of the control of the phase transition related with the latent heat and hysteresis loss and the results are contrasted with that of other candidates possessing the localized magnetic moment. Robustness of magnetocaloric effects (MCEs) against the control of T_C is presented on the ground of the fact that the latent heat is derived as △M dμ_0H_c/dT, where AM is the magnetization change at T_C. The control of T_C in La(Fe_cSi_(1-x))_(13) is closely associated with the magnetovolume effect in the IEM transition. On the other hand, the influences of the magnetovolume effect on the spontaneous magnetization M_0 and temperature dependence of the transition field of dμ_0H_c/dT are not so significant. Next, we apply the Landau expansion model to the reduction of hysteresis loss guLwith keeping the large △S_m realized by adjusting the Fe and Ce concentrations in La_(1-z)Ce_z(Fe_xSi_(1-x))_(13). As a result, the reduction of Q_(HL) is explained in terms of the band structure change and the magnetovolume effect.