ABSOLUTE VALUE OF THE MAGNETIC-MOMENT PER ATOM IN AG/FE/AG(001) AND AG/CO/AG(001) EPITAXIAL SANDWICH STRUCTURES

We present the results of an investigation of epitaxial Ag/bcc Fe/Ag(001) and Ag/fcc Co/Ag(001) sandwich structures in which we use polarized neutron reflection (PNR) as a direct probe of the absolute value of the magnetic moment per atom in order to test recent theoretical calculations for these systems. An 8-ML bcc 57Fe and a 2-ML fcc Co film were found to display planar anisotropy at 300 K from surface magneto-optic Kerr effect measurements, and were selected for PNR measurements in the temperature range 4-300 K with the films magnetically saturated in-plane. The flipping ratio observed for the 8-ML 57Fe film is consistent with a ferromagnetic moment in the range 0.9-1.1 Bohr magnetons, which is significantly reduced from the bulk value, in contrast with recent theoretical predictions of a strongly enhanced ferromagnetic moment for this epitaxial system. No temperature dependence of the magnetization is detected, confirming the anticipated bulklike behavior. For the 2-ML fcc Co film, the observed flipping ratio is consistent with a ferromagnetic moment in the range 1.8-2.2 Bohr magnetons, which is significantly enhanced from the bulk hcp value, in agreement with recent theoretical calculations. No temperature dependence of the Co magnetization was detected.