  The structural, magnetic, transport, thermal and magnetothermal properties of
quaternary Heusler alloys Ni50Mn38-xFexSb12 have been studied. Powder x-ray
diffraction and temperature dependence of magnetization studies reveal that
with addition of Fe in Mn site, the martensitic transition shifts to lower
temperatures. It is also found that the martensitic transition becomes broader
for the higher Fe concentrations. The metamagnetic transition in M(H) isotherms
becomes very prominent in x=2 and vanishes for x=3 and 4. A maximum positive
magnetic entropy change of 14.2 J/kg K is observed for x=2 at 288 K for 50 kOe.
Resistivity shows an abrupt decrease across the martensitic transition in all
the alloys, except x=6, which does not have the martensitic transition. Maximum
negative magnetoresistance of 21% has been obtained for x=2 at 50 kOe. The same
alloy also shows an exchange bias field of 288 Oe.
