title: Magnetism and exchange interaction of small rare-earth clusters; Tb as a representative.
abstract: Here we follow, both experimentally and theoretically, the development of magnetism in Tb clusters from the atomic limit, adding one atom at a time. The exchange interaction is, surprisingly, observed to drastically increase compared to that of bulk, and to exhibit irregular oscillations as a function of the interatomic distance. From electronic structure theory we find that the theoretical magnetic moments oscillate with cluster size in exact agreement with experimental data. Unlike the bulk, the oscillation is not caused by the RKKY mechanism. Instead, the inter-atomic exchange is shown to be driven by a competition between wave-function overlap of the 5d shell and the on-site exchange interaction, which leads to a competition between ferromagnetic double-exchange and antiferromagnetic super-exchange. This understanding opens up new ways to tune the magnetic properties of rare-earth based magnets with nano-sized building blocks.
authors.affiliation: Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
authors.forename: Lars
authors.initials: L
authors.lastname: Peters
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
authors.forename: Biplab
authors.initials: B
authors.lastname: Sanyal
authors.affiliation: Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Chris
authors.initials: C
authors.lastname: van Dijk
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
authors.forename: John
authors.initials: J
authors.lastname: Bowlan
authors.affiliation: School of Physics, Georgia Institute of Technology, 837 State Str., Atlanta, Georgia 30332, USA.
authors.forename: Walt
authors.initials: W
authors.lastname: de Heer
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.|Department of Materials and Nanophysics, School of Information and Communication Technology, Electrum 229, Royal Institute of Technology (KTH), SE-16440 Kista, Sweden.|SeRC (Swedish e-Science Research Center), KTH, SE-10044 Stockholm, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Delin
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
authors.forename: Igor
authors.initials: I
authors.lastname: Di Marco
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
authors.forename: Olle
authors.initials: O
authors.lastname: Eriksson
authors.affiliation: Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.|Department of Theoretical Physics and Applied Mathematics, Ural Federal University, 620002 Ekaterinburg, Russia.
authors.forename: Mikhail I
authors.initials: MI
authors.lastname: Katsnelson
authors.affiliation: Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden.
authors.forename: Börje
authors.initials: B
authors.lastname: Johansson
authors.affiliation: Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.
authors.forename: Andrei
authors.initials: A
authors.lastname: Kirilyuk