Modeling magnetism of hexagonal Fe monolayers on 4d substrates

Mapping the total energies obtained from first principles calculations to model Hamiltonians is a powerful technique to explore the magnetic ground state of a system. We analyze the applicability of this approach in the presence of highly polarizable substrates, e. g. for an ultrathin Fe layer on Pd(111), Rh(111), Ru(0001), or Tc(0001). We find that the traditionally accepted model Hamiltonians (Heisenberg plus nearest neighbor higher-order spin Hamiltonians) are not sufficient to capture the magnetic interactions in these systems and examine new terms that can be included to improve the description. Challenges for this technique are exemplified by the double-rowwise antiferromagnetic (AFM) ground state predicted for Fe/Rh(111). (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim