The short-range and long-range diffusion of H was studied by using magnetic after-effect and thermal desorption spectroscopic techniques. It was found that the substitution of Ga for Fe greatly reduced the up-take and diffusion of H. It was noted that Fe17Sm2 exhibited an H-induced magnetic after-effect relaxation maximum at 190K, with a mean activation enthalpy of 0.48eV and a pre-exponential factor of 5 x 10-12s. In the case of Fe28Ga3, the above maximum was replaced by a double maximum at 200 and 250K. These peaks corresponded to activation enthalpies of 0.52 and 0.64eV, with a pre-exponential factor of 2 x 10-12s. The maxima were attributed to short-range H diffusion. Thermal desorption spectroscopic measurements at 291 to 515K indicated activation enthalpies of 0.59 and 0.75eV, respectively. The results were explained in terms of differing interstitial sites for H.

N.Mommer, J.Van Lier, M.Hirscher, H.Kronmuller: Journal of Alloys and Compounds, 1998, 270[1-2], 58-62