Magnetization of uncovered and V-covered ultrathin Fe(100) films on V(100)

We used polarized neutron reflectometry (PNR) to determine the absolute magnetic moment of uncovered and V-covered Fe films in the thickness range from 0.3 to 5.5 nm. The films were prepared by molecular beam epitaxy on a V(100) buffer layer grown on a MgO(100) crystal. The magnetic moment shows a linear dependence on the Fe film thickness with a reduction (compared to the Fe bulk value) of the magnetic moment equivalent to 0.1 nm bulk Fe for the V-covered films and a reduction equivalent to 0.03 nm bulk Fe for the uncovered Fe films. For the case of the V/Fe/V samples we observe a much smaller reduction of the magnetic moment than reported for experiments on Fe/V multilayers. As theoretical calculations show a strong decrease of the magnetic moment for an interface alloy we conclude that the larger reduction of the magnetization in Fe/V multilayers is due to an increase in interface roughness with increasing film thickness. For the uncovered Fe(100) films we find a much smaller reduction of the magnetic moment than in earlier in situ PNR experiments on V(110)/Fe(110) where we observed a reduction equivalent to 0.4 nm bulk Fe.