Magnetic relaxation of hydrogen in RE2Fe17 compounds (RE = Dy, Gd, Y, Nd or Sm)

The short-range diffusion of hydrogen in RE2Fe17 (RE = Dy, Gd, Y, Nd or Sm) intermetallic compounds was investigated by magnetic after-effect (MAE) me asurements. After charging the powder samples in a high-purity H-2 atmosphe re (0.13 MPa; 473 K) for 2 days, the hydrogen concentrations for DY2Fe17H4. 4, Gd2Fe17H3.8, Y2Fe17H3.0, Nd2Fe17H3.5 and Sm2Fe17H5.0 were determined by thermal desorption spectroscopy. Charged samples show several hydrogen-indu ced MAE relaxation maxima in the temperature range between SO and 220 K. Th ese relaxation maxima are assigned to jumps of hydrogen atoms between vario us interstitial sites and discussed with respect to possible diffusion path s. Numerical evaluation yielded activation enthalpies of Q = 0.46, 0.46, 0. 49, 0.48 and 0.42 eV for Gd2Fe17, Y2Fe17, Nd2Fe17, Sm2Fe17 and Dy2Fe17 resp ectively, for jumps of hydrogen between octahedral sites which are part of the long-range diffusion paths in these compounds as well.