DIFFUSION OF HYDROGEN IN NANOCRYSTALLINE PD3FE

Nanocrystalline Pd3Fe alloys with a grain size of 10 nm and 50 nm were prepared by dc-sputtering and ion-beam sputtering, respectively. The magnetic relaxation of hydrogen, i.e. the short-range diffusion of hyd rogen, has been investigated. The sputter deposited films exhibit a br oad relaxation spectrum, whereby the temperatures of the relaxation pe aks depend on the hydrogen concentration. The topological and chemical environment of the hydrogen atoms is identified by their characterist ic relaxation behaviour. In the nanocrystalline alloys hydrogen prefer entially occupies sites within the grain boundaries. A comparison of t hese results with relaxation measurements of hydrogen in crystalline P d3Fe alloys shows that the interstitial sites favoured by hydrogen are chemically surrounded by either one Fe and five Pd or two Fe and four Pd atoms. Furthermore, the sites are topologically disordered.