Martensitic transition and magnetocaloric properties in Ni 45Mn 44− xFe xSn 11 alloys

Abstract

The structural, martensitic transition and magnetocaloric effect in Heusler alloys Ni 45Mn 44− x Fe x Sn 11 ( x = 0, 2, 5 and 8) have been studied by means of XRD, SEM/EDS and magnetization measurements. The alloys with x = 2 and 5 exhibit the co-existence of orthorhombic (S.G. Pmma) martensite phase and cubic L2 1 structure (S.G. Fm-3m) austenite phase at room temperature. The martensitic transition temperature, M s , shows a non-monotonic dependence on the Fe content. M s increases from 265 K in the undoped alloy to 310 K with the addition of 2 at.% Fe, whereas further increase in Fe content to 5 and 8 at.% leads to the decrease of M s to 290 and 207 K. Substitution of Fe for Mn slightly increases the Curie temperature of austenite phase and the thermal hysteresis. Associated with the martensitic transition, the maximum magnetic entropy changes under a magnetic field change of 20 kOe are 10.6, 6.4 and 5.6 J/kg K for x = 0, 5 and 8, respectively.