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Effect of Fe substitution on the magnetic, transport, thermal and magnetocaloric properties in Ni50Mn38-xFexSb12 Heusler alloys

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.