Ferromagnetic nickel-copper alloys can be charged with cathodic hydrogen in high concentrations whereby they loose their ferromagnetic behavior. Measurements of magnetization of these alloys show a quicker absorption of hydrogen compared to nickel. The interstitial occlusion of hydrogen gives rise to a reversible lattice expansion of some percent (without change of structure). During the desorption there appear on the studied alloys (10 to 35%) simultaneously two different values of lattice parameters. This is due to the transition between two NiCu-H phases of different H-con-centrations (β- and α-phase). With increasing Cu-content a decreasing lattice expansion of the hydrogen-rich non-ferromagnetic phase is found. This expansion up to a Cu-content of 35% is proportional to the mean magnetic moment per atom of the corresponding hydrogen-free alloy. The comparison with the quantity of absorbed hydrogen suggests further - in analogy to Vegards law for mixed crystals - proportionality between lattice expansion of the β-phase (as function of the Cu-content) and the corresponding atomic ratio hydrogen/metal. The results can be understood as a decrease of the solubility of hydrogen caused by the increased filling of the d-holes by s-electrons of Cu. - Further X-ray studies showed an overcharging effect by an additive continuous increase of the lattice parameters of the β-phase.
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A Journal of Physical Sciences: Zeitschrift für Naturforschung A (ZNA) is an international scientific journal which publishes original research papers from all areas of experimental and theoretical physics. In accordance with the name of the journal, which means “Journal for Natural Sciences”, manuscripts submitted to ZNA should have a tangible connection to actual physical phenomena.