Heat treatment induced martensitic accommodation and adaptive anisotropy in melt spun Ni55Mn22Ga23 (at. %) ribbons

The effect of annealing on melt spun Ni55Mn22Ga23 (at. %) ribbon has been addressed in terms of structural, thermal, thermomagnetic, and magnetic field induced strain (MFIS) behaviour. In comparison to as-spun ribbons, the samples annealed within the L21 domain at 1073 K for 30 h with subsequent furnace cooling, showed a rise in martensitic transformation temperature. This was endorsed from electron microscopy studies revealing change in morphology of martensite plate and stacking of dislocations in a preferential orientation. The mechanism is associated to martensitic accommodation which enhanced ferro-elastic magnetic coupling and also lowered magnetic coercivity. Such accommodations and adaptive anisotropy improved the MFIS behavior in the annealed sample.