Structural Relation between the X-Phase and other Phases in Ni₂MnGa

Abstract

Abstract. We have investigated stress and temperature dependences of the structure of the X-phase in Ni 2 MnGa to understand structural relation between the X-phase and other phases. Position and intensity of satellites of the X-phase are different from those of the intermediate (I-) phase under compressive stress, but they approach those of the I-phase with decreasing stress. That is, the structure change associated with the I → X transformation is discontinuous under a compressive stress, while it is continuous under zero stress. In addition, the transformation from the X-phase to the L2 1 -type parent phase is continuous regardless of applied stress. These results strongly suggest the existence of multi-critical point in Ni 2 MnGa. On the other hand, the transformation from the X-phase to the martensite phase is discontinuous regardless of applied stress.

Magnetic shape memory effect and highly mobile twin boundaries

“…Apart from these basic phases, other phases are invariably reported as having different modulation sequences or observed X-phase. 89,90 The entire sequence of martensite phases observed on cooling can be also induced by mechanical loading of the parent phase. 74 The intermartensitic transformation and its reversibility are highly sensitive to internal stresses 91,92 which is believed to be due to the similar free energies of the different martensite structures.…”