Martensitic transformation in a ferromagnetic Co–Ni–Ga single crystal

The results of mechanical and magnetic characterization of martensitic transformation in a single crystalline ferromagnetic Co49.0Ni22.0Ga29.0 alloy are presented. The transformation behavior is experimentally found to be characterized by an enlarged temperature hysteresis (30 K) on the calorimetric and magnetic susceptibility curves and stress hysteresis (over 200 MPa) on stress–strain dependencies. The linear dependence of the critical stress to induce martensite as a function of temperature is quantitatively described by a Clausius–Clapeyron equation. The different results are compared to the Ni–Mn–Ga system and discussed, resulting in scarce possibilities for this Co–Ni–Ga alloy to exhibit the large magnetostrain effect (“magnetic shape memory”) observed in several Ni–Mn–Ga alloys.