Characteristics of the premartensitic transition strain in ferromagnetic shape memory Ni50.5Mn24.5Ga25single crystals

By measuring the strain across the premartensitic transition without and with external dc magnetic fields applied along the [001] and [010] directions of the parent phase, respectively, the characteristics of the premartensitic transition strain is investigated in detail. It was found that not only does the premartensitic transition temperature pronounce a more rapid decrease, but the premartensitic transition strain also exhibits a larger change for a field applied along the [010] direction than does a field along the [001] direction. In accord with a previous model, the present results confirm that the magnetoelastic interaction is responsible for the premartensitic transition, and the magnitude of the magnetoelastic interaction in the [010] direction is stronger than that in the [001] direction.