Complex trend of magnetic order in Fe clusters on 4$d$ transition-metal   surfaces
  We demonstrate the occurrence of compensated spin configurations in Fe clusters and monolayers on Ru(0001) and Rh(111) by a combination of X-ray magnetic circular dichroism experiments and first-principles calculations. Our results reveal complex intra-cluster exchange interactions which depend strongly on the substrate 4$d$-band filling, the cluster geometry as well as lateral and vertical structural relaxations. The importance of substrate 4$d$-band filling manifests itself also in small nearest-neighbor exchange interactions in Fe dimers and in an nearly inverted trend of the Ruderman-Kittel-Kasuya-Yosida coupling constants for Fe adatoms on the Ru and Rh surface. 
V. Sessi, F. Otte, S. Krotzky, C. Tieg, M. Wasniowska, P. Ferriani, S.   Heinze, J. Honolka, and K. Kern
cond-mat.mtrl-sci