Magnetization of ultrathin bcc Fe films on MgO

The magnetization of body-centered-cubic iron was measured by means of polarized neutron reflection on a set of films of different thickness (4, 6, 8, and 16 {}). The films were epitaxially deposited onto polished (100) MgO substrates and covered by protective layers of gold. The results show that at 40 K all films are ferromagnetic, with an average magnetic moment per iron equal to 2.2±{}0.2μB regardless of film thickness. However, the thinnest films exhibit a Curie temperature lower than that of the bulk and a magnetization axis tilted out of the film surface. These results are discussed in the light of the detailed morphology of the films, and compared with the theoretical predictions.