Measurement independent magnetocaloric effect in Mn-rich Mn-Fe-Ni-Sn (Sb/In) Heusler alloys

Abstract

We report a systematic study on the magneto-structural transition in Mn-rich Fe-doped Mn-Fe-Ni-Sn(Sb/In) Heusler alloys by keeping the total valence electron concentration (e/a ratio) fixed. The martensitic transition (MT) temperature is found to shift by following a proportional relationship with the e/a ratio of the magnetic elements alone. The magnetic entropy change (ΔSM) across MT for a selected sample (Mn49FeNi40Sn9In) has been estimated from three different measurement methods (isofield magnetization (M) vs temperature (T), isothermal M vs field (H) and heat capacity (HC) vs T). We observed that though the peak value of ΔSM changes with the measurement methods, the broadened shape of the ΔSM–T curves and the corresponding cooling power (∼140 Jkg−1) remains invariant. The equivalent adiabatic temperature change (ΔT) ∼−2.6 K has been obtained from indirect measurements of ΔT. Moreover, an exchange bias field ∼783 Oe at 5 K and a magnetoresistance of −30% are also obtained in one of these materials.