Anomalous microstructure and magnetocaloric properties in off-stoichiometric La–Fe–Si and its hydride

In the present work we reported the phase formation, microstructure, magnetocaloric effect and hydrogenation behavior of La-rich La 1.7 Fe 11.6 Si 1.4 alloy. In this off-stoichiometric La(Fe,Si) 13 alloy, the NaZn 13 -type La(Fe,Si) 13 matrix phase shows faceted grains, with the Cr 5 B 3 -type La 5 Si 3 used as the secondary phase distributed intergranularly. Such a peculiar morphology quickly forms upon one day annealing. In La 1.7 Fe 11.6 Si 1.4 alloy, we have observed a significant field dependence of magnetostructural transition temperature (∼ 6.3 K/T), resulting in a large and table-like entropy change (Δ S ∼ 18 J/kg·K in 2 T) over a broad temperature range (∼ 10 K). Upon hydrogenation, the maximum value of Δ S keeps almost unchanged, while the Curie temperature increases up to 350 K. These results indicate that the investigated off-stoichiometric La(Fe,Si) 13 alloy is a promising magnetic material for magnetic refrigerators.