Martensitic transition, magnetic, magnetocaloric and exchange bias properties of Fe-substituted Mn-Ni-Sn Heusler alloys

In this report, effect of Fe substitution on martensitic transition, magnetic, magnetocaloric and exchange bias (EB) properties of Mn50Ni40−xFexSn10 (x=0, 0.5, 1, 1.5, 2 and 3) Heusler alloys series has been investigated systematically. Fe substitution has been found to affect the ferromagnetic/antiferromagnetic interactions significantly in both the martensite and austenite phases. Martensitic transition temperature decreases with increasing Fe content, which is attributed to the decrease in number of average valence electrons per atom (e/a ratio) of these alloys. Large magnetic entropy change (ΔSM) and refrigerant capacity (RC) have been observed in these alloys, as a maximum ΔSM of ~12.6 J/kg. K is observed for composition x=0.5. Present alloys have also been found to show large exchange bias properties, as maximum exchange bias fields (HEB) of 890 Oe and 810 Oe are observed for x=0 and 0.5, respectively at 5 K. Composition and temperature dependencies of EB are associated with the change in exchange anisotropy at interfaces of competing magnetic phases. Study of minor loop and training effect also corroborates with the presence of EB in these alloys.