Effect of Al doping on structural and magnetic properties of Ni50Mn37AlxSb13−x alloy

The Ni50Mn37AlxSb13−x (x=0, 1, 3 and 5) alloys were prepared by tri-arc melting technique. The replacement of Sb by Al increases the martensitic transformation temperature (TM) as well as ferromagnetic to paramagnetic transformation temperature (TCA) within the austenite phase. The increase in TM is found to due to the enhancement of hybridization between 3d states of Ni and Mn atoms. We also observed a large exchange bias field (HEB) of 470 Oe for x=0 and it decreases with the Al concentration for field cooled (FC) magnetic hysteresis loop. A large magnetic entropy change (ΔSM) of 10 J/kg-K is found for x=1 alloy under a field change (ΔH) of 50 kOe and it decreased for further higher concentration of Al doping. The possible reasons for observed behaviors are discussed.