In-Situ High-Energy X-Ray Diffuse-Scattering Study of the Phase Transition of Ni 2 MnGa Single Crystal under High Magnetic Field

The defects-related microstructural features connected to the premartensitic and martensitic transition of a Ni 2 MnGa single crystal under a high magnetic field of 50 KOe applied along the [ 11̅0] crystallographic direction of the Heusler phase were studied by the in-situ high-energy X-ray diffuse-scattering experiments on the high energy synchrotron beam line 11-ID-C of APS and thermomagnetization measurements. Our experiments show that a magnetic field of 50 KOe applied along the [ 11̅0] direction of the parent Heusler phase can promote the premartensitic transition of Ni 2 MnGa single crystal, but puts off martensite transition and the reverse transition. The premartensitic transition temperature ( T PM ) increases from 233 to 250 K (−40 to −23 °C). The martensite transition start temperature ( M s ) decreases from 175 to 172 K (−98 to −101 °C), while the reverse transition start temperature ( A s ) increases from 186 to 189 K (−87 to −84 °C). The high magnetic field leads to a rapid rearrangement of martensite variants below the martensite transition finish temperature ( M f ). The real transition process of Ni 2 MnGa single crystal under the high magnetic field was in-situ traced.