Effects of hydrostatic pressure on martensitic transition, ductility, and magnetocrystalline anisotropy of Ni2MnGa

Abstract

The tuning of hydrostatic pressure on thermodynamic stability, magnetic and martensitic transition temperatures (TC, TM), bulk mechanical properties, and magnetocrystalline anisotropy in Ni2MnGa has been systematically studied using the first-principles method. The calculated formation energies indicate that the higher the pressure, the more conducive it is to the synthesis of Ni2MnGa. Application of high pressures to the austenitic phase yields a maximum increase of only approximately 17 K in TC, suggesting limited pressure dependence of TC. An increase in pressure can effectively elevate TM, especially when the pressure exceeds 9.4 GPa, TM rises above room temperature. The analysis of three classic ductile–brittle criteria: Pugh's ratio, Poisson's ratio, and Cauchy pressure coherently manifests that the applied pressure can improve the ductility of Ni2MnGa. The magnetocrystalline anisotropy of Ni2MnGa is remarkably increased by increasing pressure, and its value at 19.1 GPa increases by 56% compared to that at ambient pressure. Our findings will be helpful for future industrial applications of Ni2MnGa under hydrostatic pressure.