Magnetic study of the Ce2Fe17Hx compounds: Magnetic circular x-ray dichroism, x-ray-absorption near-edge structure, magnetization, and diffraction results

Hydrogen dynamics in Ce2Fe17H5: inelastic and quasielastic neutron scattering studies

The vibrational spectrum of hydrogen and the parameters of H jump motion in the rhombohedral Th(2)Zn(17)-type compound Ce(2)Fe(17)H(5) have been studied by means of inelastic and quasielastic neutron scattering. It is found that hydrogen atoms occupying interstitial Ce(2)Fe(2) sites participate in the fast localized jump motion over the hexagons formed by these tetrahedral sites. The H jump rate τ(-1) of this localized motion is found to change from 3.9 × 10(9) s(-1) at T = 140 K to 4.9 × 10(11) s(-1) at T = 350 K, and the temperature dependence of τ(-1) in the range 140-350 K is well described by the Arrhenius law with the activation energy of 103±3 meV. Our results suggest that the hydrogen jump rate in Th(2)Zn(17)-type compounds strongly increases with decreasing nearest-neighbor distance between the tetrahedral sites within the hexagons. Since each such hexagon in Ce(2)Fe(17)H(5) is populated by two hydrogen atoms, the jump motions of H atoms on the same hexagon should be correlated.

(Lu0.8Ce0.2)2Fe17 single crystal under hydrostatic and 'negative' pressure induced by hydrogenation

An experimental study of correlations between the magnetovolume effects and the type of magnetic ordering in the Lu(2)Fe(17)-based intermetallics is shown for the example of variation of the interatomic distances by means of substitution of Ce for Lu, hydrogenation and subsequent high-pressure investigation of both the initial (Lu(0.8)Ce(0.2))(2)Fe(17) and a hydride (Lu(0.8)Ce(0.2))(2)Fe(17)H(0.4) single-crystalline compounds. The magnetization study was carried out under hydrostatic pressures of up to ∼ 0.8 GPa. Hydrogenation is found to totally suppress the antiferromagnetic order of (Lu(0.8)Ce(0.2))(2)Fe(17) by favoring domination of the ferromagnetic interactions which increases the magnetic ordering temperature from 247 to 300 K. The application of pressure decreases the Curie temperature and induces the non-collinearity of the magnetic moments in (Lu(0.8)Ce(0.2))(2)Fe(17)H(0.4), confirming the strong influence of hydrogenation on exchange coupling.