Stress-Temperature Phase Diagram of Ni2MnGa and Structural Relations between its Constituent Phases
The ferromagnetic shape memory alloy Ni2MnGa exhibits a successive martensitic transformation from the L21-type structure to the so-called intermediate phase and then to the martensite phase with an incommensurate structure during cooling under zero stress. In addition to these phases, a new phase, which we call the X-phase, appears when Ni2MnGa is cooled under compressive stress applied in the  direction. In this paper, we discuss the structural relations between the X-phase and the other phases on the basis of experimental results of compressive tests, transmission electron microscope observations and neutron diffraction patterns. It is likely that a multicritical point exists in the stress-temperature phase diagram of Ni2MnGa.
T. Fukuda et al., "Stress-Temperature Phase Diagram of Ni2MnGa and Structural Relations between its Constituent Phases", Materials Science Forum, Vol. 684, pp. 61-71, 2011