  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 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 magnetic entropy change changes with the measurement methods, the
broadened shape of the magnetic entropy change vs T curves and the
corresponding cooling power (~140 Jkg-1) remains invariant. The equivalent
adiabatic temperature change ~ -2.6 K has been obtained from indirect
measurements of temperature change. Moreover, an exchange bias field ~ 783 Oe
at 5 K and a magnetoresistance of -30% are also obtained in one of these
materials.
