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

In La (Fex Si1-x) 13, the partial substitution of Ce for La results in the decrease of the Curie temperature TC, and the isothermal entropy change Δ Sm becomes larger with decreasing TC. The increase of Δ Sm with decreasing TC is also confirmed by applying hydrostatic pressure, although the increment of Δ Sm 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 Δ Sm. 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 Δ Sm. Therefore, it is concluded that the change in the band structure also contributes the enhancement of Δ Sm.