MAGNETISM OF FE IMPURITIES AND ADATOMS ON PD(0 0 1) SURFACES

It is well known that the giant moment associated with the substitutio nal Fe impurities in Pd can be understood in terms of a polarization c loud consisting of small induced moments in the Pd shells around the i mpurity. It is interesting to investigate if a similar phenomenon is p resent when a Pd surface is considered. Here we perform first-principl es, self-consistent electronic structure calculations, within the loca l spin density functional formalism, to obtain the magnetic behavior o f substitutional Fe impurities in Pd(0 0 1) and Fe adatoms on this sur face. We find that in both cases the Fe site has a large local moment, close to saturation. As in the case of Fe impurities in bulk Pd, a mo ment is induced on the Pd neighbors, considerably enhancing the total magnetic moment of the system. Our results indicate that the failure t o observe magnetic behavior using anomalous Hall effect experiments fo r Pd surfaces with small Fe coverages cannot be explained in terms of an antiferromagnetic coupling between the Fe impurity and its Pd neigh bors, as was previously suggested. (C) 1998 Elsevier Science B.V. All rights reserved.