Hydrogen in R(2)Fe(17) intermetallic compounds: Structural, thermodynamic, and magnetic properties

The absorption and diffusion behavior of hydrogen in iron-rich rare-earth intermetallics of the type R(2)Fe(17) (R = Y, Sm, Gd) and the resulting changes of their magnetic properties are investigated. Intermediate hydrogen concentration indicate the solid-solution character of the hydrides. From equilibrium and nonequilibrium absorption experiments net reaction energies, bulk diffusion constants, and surface barrier energies for Sm2Fe17 are determined and discussed. The low-temperature quantum diffusion is discussed for the hydride and the corresponding nitride. The interstitial modification changes drastically the crystalline electric field in the rare-earth intermetallics. For Sm2Fe17H4 the crystalline electric-field parameter A(20) = 110 Ka(0)(-2) is estimated from the anisotropy constants K-1 and K-2.