MAGNETIC-PROPERTIES OF ULTRATHIN BCC FE(001) FILMS GROWN EPITAXIALLY ON AG(001) SUBSTRATES

We have used polarised neutron reflection (PNR) to determine the absolute value of the ground state magnetic moment per atom of a Au/9 ML bcc Fe/Ag(001) epitaxial sandwich and of a Au/3 ML bcc Ni/5 ML bcc Fe/Ag(001) epitaxial sandwich grown by MBE. For the 9 ML Fe sample, we deduce a ferromagnetic moment per Fe atom in the range 1.9-2.2-mu-B, close to the bulk value and in agreement with FMR results. By comparing these results with that of a reduced Fe moment previously obtained for a Ag/8 ML Fe/Ag(001) sample, we conclude that extremely high quality epitaxial growth is likely to be required to test the recent theoretical predictions of enhanced moments in such ultrathin Fe layers. For the 3 ML Ni/5 ML Fe sample the data are consistent with a moment per Fe atom of at least the bulk value of 2.2-mu-B, a moment per Ni atom of at least 0.55-mu-B and ferromagnetic coupling between the Fe and Ni layer magnetisations.