Influence of partial substitution of Ce on the Curie temperature and magnetic entropy change In itinerant-electron metamagnetic La(Fe_xSi_(1-x))_(13) compounds

摘要

In La(Fe_xSi_(1-x))_(13), the partial substitution of Ce for La results in the decrease of the Curie temperature Tc, and the isothermal entropy change DELTA S_m becomes larger with decreasing T_c. The increase of DELTA S_m with decreasing T_c is also confirmed by applying hydrostatic pressure, although the increment of DELTA S_m is not so large. Accordingly, another effect addition to the reduction of volume due to the small ionic radius of Ce should be considered for the enhancement of DELTA S_m. From the fitted isothermal magnetization curves, it is evident that the partial substitution of Ce enhances the thermal variation of the forth-order coefficient B(T) in the Landau expansion of the Gibbs free energy, being consistent with the increase of DELTA S_m. Therefore, it is concluded that the change in the band structure also contributes the enhancement of DELTA S_m.