Martensitic transition and magnetocaloric properties in Ni45Mn44−xFexSn11 alloys

The structural, martensitic transition and magnetocaloric effect in Heusler alloys Ni45Mn44−xFexSn11 (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 L21 structure (S.G. Fm-3m) austenite phase at room temperature. The martensitic transition temperature, Ms, shows a non-monotonic dependence on the Fe content. Ms 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 Ms 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.

Research highlights▶ The martensitic transition temperature, Ms, shows a non-monotonic dependence on the Fe content. ▶ The values of maximum magnetic entropy change ΔSM in the vicinity of the martensitic transition are insensitive to the Fe content. The ΔSM for alloy Ni45(Mn39Fe5)Sn11 is 6.4 J/kg K at 286 K for a magnetic field change of 20 kOe.