Effect of chemical and external hydrostatic pressure on magnetic and magnetocaloric properties of Pt doped Ni2MnGa shape memory Heusler alloys

Abstract

The magnetocaloric effect (MCE) on Ni2−xPtxMnGa (x = 0.2, 0.3 and 1.0) shape memory Heusler alloys around martensite phase transition temperature (TM) is investigated by varying chemical pressure (Pt concentration). The magnetic entropy change (ΔSM) decreases with increasing chemical pressure for various external applied magnetic fields up to 3 T, and the width of thermal hysteresis increases with the increases of Pt concentration. The effect of hydrostatic pressure on both TM and ΔSM for Ni1.8Pt0.2MnGa is also investigated. We observed that the application of hydrostatic pressure increases TM (3.5 K/GPa) and stabilizes the martensite phase. The maximum magnetic entropy change (ΔSmax) of 9.31 J Kg−1 K-1is observed for a field change of 9 T at ambient pressure for Ni1.8Pt0.2MnGa. Further, the application of external pressure leads to the decrease of ΔSmax to 5.52 J Kg−1 K−1 at 0.91 GPa.