Magnetic Moments in Rough Fe Surfaces

Epitaxial Fe(110) films on W(110) with smooth surfaces were covered by some additional Fe at lowered temperatures, to create a rough surface, showing roughly periodic arrays of atomic steps along [001], the density of which could be determined from Spot Profile Analysis Low-Energy Electron Diffraction. Annealing to a resmoothened surface was connected with a loss of magnetic moment by (1.1 ± 0.4) μ B per step atom as measured by magnetometry in situ before and after annealing. The magnetic moment of a real step atom was estimated to be (3.4 ± 0.5) μ B , definitely enhanced by roughly 0.5 μ B with respect to the atomic moment in a smooth surface. Using the theory of local moments in metals, a model of the enhanced moment is given, providing a quantitative connection between atomic moment and coordination, in good agreement with the experiments. The model assumes the weak-coupling value of six resonances below the Fermi energy, rather than five assumed by local spin density theory.