Giant magneto-caloric effect near room temperature in Ni–Mn–Sn–Ga alloys

We report the observation of giant magneto-caloric effect (MCE) in ferromagnetic shape memory alloys (FSMAs) of nominal compositions Ni2Mn1.36Sn0.64−xGax (x=0.24x=0.24, 0.28 and 0.32). Irrespective of the Ga doping, all the samples undergo long range magnetic ordering below around 330 K. However, the martensitic transition temperature (TMSTMS) of the samples varies strongly with Ga concentration. Clear signature of field-induced transition around TMSTMS is visible for all the samples. The observed MCE (ΔS=13.6 J/(kg K) for field changing from 0 to 50 kOe) is found to be highest for x=0.28x=0.28 with peak near 249 K, while x=0.32x=0.32 shows ΔS=12.8 J/(kg K) at 274 K. This series of Ga-doped alloys are found to be interesting materials with high value of ΔS over a varied range of temperature.