Electron energy loss and X-ray absorption behaviour of high density nonmagnetic cobalt

Abstract

We have studied the absorption behaviour at the L-edge of the recently discovered high density nonmagnetic (HDNM) cobalt in a polycrystalline cobalt thin film. Soft X-ray absorption spectroscopy (SXAS) experiment has shown a higher edge jump energy for HDNM cobalt compared to normal ferromagnetic cobalt. Electron energy loss spectroscopy (EELS) measurement has shown a lower absorption cross-section for HDNM cobalt compared to normal cobalt. As the thin film contained layers of HDNM Co and normal Co at different depths (Sci. Rep. 7, 41856 (2017)) a depth selective SXAS experiment was performed. In SXAS experiment the thin film sample was sputtered in order to obtain absorption spectra from different depths. We clearly observe a shift of the L-III edge energy to lower energy as soon as the high density layer is removed and normal Co layer is exposed to the X-ray beam. EELS experiments were carried out on high density grains, identified by transmission electron microscopy and Co fluorescence imaging. The results were compared with those from lower density or normal density grains. The energy loss peaks are less intense for high density cobalt.