Magnetic dichroism in Co films on Cu(001) using unpolarized light -: A thickness and temperature dependent study

The thickness and temperature dependence of the angular distribution of the magnetic dichroism in photoemission from Co 2p core levels of Co/Cu(001) ultra-thin films has been investigated, using unpolarized Mg K-alpha radiation. Photoelectron spectra were collected fur emission angles in a range of +/-9 degrees around the surface normal in the [001] azimuth. All asymmetry spectra were found to exhibit an identical spectral shape within the experimental error bar, but different scaling. The angular distribution of the Co 2p dichroic signal shows that at emission directions off the sample normal strong variations are present, in contrast to predictions from simple atomic theory. These crystallinity-related modulations were studied for Co films of different thicknesses [5, 3,2, and 1.5 atomic monolayers (ML)I and different temperatures (100 and 300 K). They are higher for thicker films and lower temperatures. This experimental finding proves a diffraction picture, in which this modulation around the surface normal is explained by diffraction effects in forward scattering along the sample normal. As diffraction effects in magnetic dichroism combine both diffraction and magnetic dichroism, its behavior is influenced by both, structural and magnetic properties of the film. (C) 2001 Elsevier Science BN. All rights reserved.