Modification of structural properties of Nb/Fe(110) multilayers via hydrogen absorption

We report on the structural effect of hydrogen loading from the gas phase o n Nb/Fe multilayers (t(Nb) = 10-1000 Angstrom). The equilibrium hydrogen co ncentration in the Nb layers and the hydrogen-induced layer thickness expan sion perpendicular to the him plane were determined as function of external hydrogen pressure by means of in situ neutron reflectivity measurements. I n situ X-ray diffraction experiments performed on the same samples yielded the corresponding expansion of the out-of-plane Nb(1 1 0) interplanar spaci ng. It was found in all samples that the relative expansion of the Nb layer s is considerably larger than the relative increase of the Nb(1 1 0) interp lanar spacing, indicating a second absorption mechanism aside from the well -known incorporation of hydrogen at interstitial sites of the host metal. ( C) 2000 Elsevier Science B.V. All rights reserved.