Control of Phase Transformation Temperatures by Substituents in Ni-Fe-Ga Ferromagnetic Shape Memory Alloys

Abstract

The variations of the martensitic transformation starting temperature T_M^S and the Curie temperature T_C in Ni-Fe-Ga alloys have been investigated by substituting with several kinds of the fourth elements. By partial substitution of Co or Cu for Ni, T_C increases and T_M^S decreases. In particular, the increase of T_C is remarkable in the Ni_54−xCo_xFe₁₉Ga₂₇ alloy, which is related to the strong Ni-Co and Co-Fe exchange interactions. For the Ni₅₄Fe_19−xMn_xGa₂₇ alloys, T_C slightly increases with the increase of Mn content, in analogy with the Ni₅₂Fe_xMn_21−xGa₂₇ alloys. From the present study, it is demonstrated that both T_C and T_M^S of the Ni-Fe-Ga alloys can be effectively controlled by selecting the substituents.