Electronic structure changes associated with a martensitic transformation in a Ti50Ni48Fe2 alloy studied by electron energy-loss spectroscopy

Changes in the 3d occupancy associated with a martensitic transformation in a Ti50Ni48Fe2 alloy was investigated by electron energy-loss spectroscopy (EELS). The white-line intensity of both Ti- and Ni-L-2,L-3, edges,which reflects the unoccupied density-of-states in 3d band, was compared before and after the martensitic transformation, where the intensity change was observed by both the peak intensity and the integrated intensity measurements. It was found that the white-line intensity of Ti-L-2,L-3 edges in the parent phase (cubic) was slightly larger than that in the martensite (monoclinic), whereas the intensity of Ni-L-2,L-3, edges in the parent phase was slightly smaller than that in the martensite. The result indicates that the unoccupied density-of-states in Ti-3d band tend to be reduced with the cubic to monoclinic martensitic transformation, while those in Ni-3d band to be increased. The present investigation, where core-loss measurements of EELS were applied for a martensitic transformation for the first time, convinced that EELS is sensitive to observe small electronic structure changes with this type of transformation.