Continuous and Reversible Change of the Magnetic Coupling in an Fe/Nb Multilayer Induced by Hydrogen Charging

We show in this Letter that the magnetic coupling of a $[26Å\mathrm{Fe}/15\mathrm{}Å\mathrm{Nb}]\times 18$ multilayer is changed in a continuous and reversible way by introducing hydrogen into the sample. The magnetic structure and its change during hydrogen charging (and the following decharging) is measured in situ by neutron reflectivity. The alteration of the magnetic coupling upon hydrogenation is confirmed by SQUID magnetization measurements. We attribute the change of the coupling to a change of the effective Fermi wave vector in Nb due to hydrogen uptake.