Magnetism of Fe impurities and adatoms on Pd(0 0 1) surfaces

It is well known that the giant moment associated with the substitutional Fe impurities in Pd can be understood in terms of a polarization cloud consisting of small induced moments in the Pd shells around the impurity. It is interesting to investigate if a similar phenomenon is present when a Pd surface is considered. Here we perform first-principles, self-consistent electronic structure calculations, within the local spin density functional formalism, to obtain the magnetic behavior of substitutional Fe impurities in Pd(0 0 1) and Fe adatoms on this surface. 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 moment is induced on the Pd neighbors, considerably enhancing the total magnetic moment of the system. Our results indicate that the failure to observe magnetic behavior using anomalous Hall effect experiments for Pd surfaces with small Fe coverages cannot be explained in terms of an antiferromagnetic coupling between the Fe impurity and its Pd neighbors, as was previously suggested. (C) 1998 Elsevier Science B.V. All rights reserved.