Abnormal e/a-dependence of TM and large inverse magnetocaloric effect in Ni49−xCuxMn39Sb12 alloys

The influence of Cu substitution for Ni on magnetic properties and magnetic entropy change has been investigated in the Ni49−xCuxMn39Sb12 alloys with x = 0, 1 and 2. With increasing Cu content from x = 0 to 2, a decreasing dependence of the martensitic transformation temperature (TM) on the number of valence electrons per atom (e/a) is observed, which cannot be explained by the size factor or the number of valence electrons per atom. An inverse magnetocaloric effect was observed in the vicinity of the first order martensitic transition. The maximum value of −ΔSMmax in the nominal Ni48Cu1Mn39Sb12 alloy is 9.38 J kg−1 K−1 at 291 K for a magnetic field change from 0 to 5 T, with the refrigerant capacity of 25.9 J kg−1. The large ΔSM indicate that nominal Ni48Cu1Mn39Sb12 alloy may be a promising candidate for magnetic refrigeration at room temperatures.