Direct Observation of Magnetic Friedel Oscillation at the Fe (001) Surface

Abstract

The surface magnetism of Fe (001) was studied in an atomic layer-by-layer fashion by using the in situ ⁵⁷Fe probe layer method with a synchrotron Mössbauer source. The observed internal hyperfine field H_int exhibits a marked decrease at the surface and an oscillatory behavior with increasing depth in the individual upper four layers below the surface. The calculated layer-depth dependencies of the effective hyperfine field, |H_eff|, isomer shift, δ, and quadrupole shift, 2ε, agree well with the observed experimental parameters. These results provide the first experimental evidence for the magnetic Friedel oscillations, which penetrate several layers from the Fe (001) surface.