Pressure effects on the magnetocaloric properties of Ni-rich and Mn-rich Ni2MnGa alloys

The pronounced magnetocaloric properties of Ni27xMn17yGa17z alloys are strongly dependent on both the composition and the inter-atomic distances. Moreover, the off-stoichiometric Mn- and Ni-rich Ni2MnGa compounds exhibit mutually different magnetocaloric behaviour under high hydrostatic pressure. A pressure-induced co-occurrence of martensitic transformation and magnetic transition was found for Mn-rich compounds, resulting in a substantial increase of magnetocaloric effect. In contrast to this, the magnetocaloric effect was partially suppressed in the Ni-rich compounds under high pressure. These results reflect the specific role of Ni in the martensitic transformation of Ni2MnGa alloys.