Effect of Sn doping on the martensitic and premartensitic transitions in Ni2MnGa

The effect of Sn doping at the Ga site of Ni2MnGa is investigated through magnetic and magneto-transport measurements. Clear signatures of martensitic and premartensitic transitions are observed in the pure as well as in 5% Sn doped alloy. For 10% Sn doping, the martensitic transition vanishes, while the premartensitic transition remains visible at low temperature. All the samples are found to have a ferromagnetic ground state with saturation moment decreasing with increasing Sn concentration. The magnetocaloric effect near the martensitic transition in the pure and 5% Sn doped samples is found to be positive. However, the entropy change is found to decrease with increasing magnetic field, which is particularly prominent in the undoped sample. The samples also show negative magnetoresistance with anomalies at the martensitic and premartensitic transition points.

► Large change in martensitic and premartensitic transition on very small amount of Sn doping in Ni2MnGa.
► Substantial decrease in magnetic moment in the alloys by the substitution of Sn at the Ga site of Ni2MnGa.
► Signature of inverse magnetocaloric effect is observed in certain doped compositions.
► Chemical pressure effect is found to be an important parameter in deciding the structural and magnetic properties of the doped alloys.