X-ray diffraction study of the structural phase transition of Ni2MnGa alloys in high magnetic fields

The Ni2MnGa alloys have been systematically studied in a wide temperature range at different fields, by means of a low temperature X-ray diffraction apparatus in high magnetic fields. Using the width of the (220) diffraction peak as a measure of the degree of transformation to the low-temperature tetragonal phase, two kink anomalies in the temperature dependence of (220) peak width were detected, both on cooling and warming, between the parent and martensitic phases, corresponding to the martensitic transition-temperature (Tm) and premartensitic transition-temperature (Tp), respectively. Furthermore, effects of the magnetic field were also clearly observed.