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

• The magnetic and magnetocaloric property is investigated for Pt doped Ni 2− x Pt x MnGa (x = 0.2, 0.3 and 1.0) alloys at ambient pressure. • The pressure also induces the AFM/FM interaction at low temperature for x = 0.2 alloy, where previously not observed in Ni-Mn based alloys under pressure. • The metamagnetic transition and crossover of magnetization are suppressed for x = 1.0 alloy. • The application of chemical and hydrostatic pressure increases the T M and decreases Δ S M. The magnetocaloric effect (MCE) on Ni 2− x Pt x MnGa (x = 0.2, 0.3 and 1.0) shape memory Heusler alloys around martensite phase transition temperature (T M) is investigated by varying chemical pressure (Pt concentration). The magnetic entropy change (Δ S M) 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 T M and ΔS M for Ni 1.8 Pt 0.2 MnGa is also investigated. We observed that the application of hydrostatic pressure increases T M (3.5 K/GPa) and stabilizes the martensite phase. The maximum magnetic entropy change (Δ S max) of 9.31 J Kg−1 K-1is observed for a field change of 9 T at ambient pressure for Ni 1.8 Pt 0.2 MnGa. Further, the application of external pressure leads to the decrease of ΔS max to 5.52 J Kg−1 K−1 at 0.91 GPa. [ABSTRACT FROM AUTHOR]