The incommensurate modulations of stoichiometric Ni2MnGa

We use X-ray diffraction to confirm that the 5M phase of the stoichiometric Heusler alloy Ni2MnGa has an incommensurate modulation with wavevector q=[0.4280.4280]. We find the crystal to be macroscopically twinned with a structure well described by the theory of martensitic phase transitions, though theoretical calculations of the X-ray diffraction rule out the existence of an adaptive phase. The premartensite phase is found to be slightly incommensurate with q=[0.3410.3410].