Real time monitoring of twin boundary motion in polycrystalline magnetocaloric Ni2+xMn1−xGa by in situ focused ion beam microscopy

Polycrystalline Ni-Mn-Ga intermetallics were studied for their potential in magnetic refrigeration near room temperature. Previous research has shown an interrelation between entropy change and magnetocrystalline anisotropy. In this work, the influence of mechanical stress on magnetocrystalline anisotropy was studied. Both, uncontrolled processing and defined in situ mechanical loading with focused ion beam imaging were used to show the influence of initial directional solidification and the relationship between compressive stress and movement in twin boundaries in the martensite phase.