MAGNETIC-X-RAY DICHROISM IN 2P ABSORPTION-SPECTRA OF FE CU(001)/

Large magnetic circular dichroism using circularly polarized synchrotr on radiation has been observed at the L2,3 absorption edges of thin ( 1-12 monolayers) fcc Fe films grown on Cu(001). Dramatic changes in th e 2p branching ratio are observed when the orientation of photon helic ity and sample magnetization are varied from parallel to antiparallel. The temperature and film thickness dependence of the perpendicular an isotropy in these films could be monitored by variations in the 2p bra nching ratio. Finally, our results are described in a simple theoretic al framework that allows a determination between the predicted low- an d high-spin phases for fcc Fe. Our data suggest a high-spin phase with a moment of 2.0-2.5 mu(B)/atom. Interestingly, thicker films with rem anant magnetic moments in the film plane present smaller branching rat io variations consistent with either a reduced moment or with domain c losure for these films. The surface sensitivity and elemental specific ity of this technique make it particularly attractive for the study of surface and thin film magnetism.