Magneto-thermal and magneto-transport behavior around the martensitic transition in Ni50−xCoxMn40Sb10 (x = 9, 9.5) Heusler alloys

The structural, magnetic, magnetocaloric and magnetoresistance behavior in Ni50−xCoxMn40Sb10 (x = 9 and 9.5) has been studied around the magnetostructural transition. The X-ray diffraction results at room temperature show that the compound with x = 9 is predominantly martensitic whereas the one with x = 9.5 is austenite in nature. The maximum magnetic entropy change of 9.2 J kg−1 K−1 was achieved in x = 9.5 at 246 K in a field of 50 kOe and a value of 8.2 J kg−1 K−1 was found near room temperature for x = 9. The effective refrigeration capacity of 106 J/kg has been calculated for x = 9, which is larger than the same observed in other Ni–Mn based Heusler alloy systems. A large magnetoresistance of 25% was obtained around room temperature for x = 9. The large difference in the magnetization between the martensitic and austenite phases is responsible for the large magnetocaloric effect and magnetoresistance in these compounds.