Magnetism Of Ordered Sm/Co(0001) Surface Structures

The epitaxial system Sm/Co(0001) was studied for Sm coverages up to 1 monolayer (ML) on top of ultrathin Co/W(110) epitaxial films. Two ordered phases were found for 1/3 and 1 ML Sm, respectively. The valence state of Sm was determined by means of photoemission and magnetic properties were measured by magneto-optical Kerr effect. We find that 1 ML Sm causes a strong increase of the coercivity with respect to that of the underlying Co film. Element-specific hysteresis loops, measured by using resonant soft x-ray reflectivity, show the same magnetic behavior for the two elements.