Discussion (2)
The imposed cathodic current during the electrochemical hydriding sustains two possible processes: hydrogen evolutiuon (her) and IMC hydrogenation following the paths indicated in Fig 4. Hydrogen intercalated occupy space available into the lattice and the hydrogenated front move from the electrolyte/electrode interface to the IMC bulk by diffusion.
Since the 4f shell of Gd atoms is well localised it’s little affected from hydrogen absorption the initial decrease in magnetisation may be due to the filling of the hybrid d-band (3d-5d) which probably causes an initial decrease in the density of states (DOS) at the Fermi level (with subsequent rise of the Co magnetic moment and decrease of magnetisation) followed by an increase of DOS for further filling of the band. Therefore the subsequent rise in magnetisation may be due to both the weakening of the R-Co exchange interactions following the crystal lattice expansion and to the decrease of the Co magnetic moment due to the electron transfer from the hydrogen. Since the compound is a collinear ferrimagnet a decrease in the cobalt moment which opposes the Gd one results in a comprehensive increase of magnetisation.