The role of magnetic anisotropy in the Kondo effect

Alexander F. Otte, Markus Ternes, Kirsten Von Bergmann, Sebastian Loth, Harald Brune, Christopher P. Lutz, Cyrus F. Hirjibehedin, Andreas J. Heinrich

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In the Kondo effect, a localized magnetic moment is screened by forming a correlated electron system with the surrounding conduction electrons of a non-magnetic host. Spin S=1/2 Kondo systems have been investigated extensively in theory and experiments, but magnetic atoms often have a larger spin. Larger spins are subject to the influence of magnetocrystalline anisotropy, which describes the dependence of the magnetic moment's energy on the orientation of the spin relative to its surrounding atomic environment. Here we demonstrate the decisive role of magnetic anisotropy in the physics of Kondo screening. A scanning tunnelling microscope is used to simultaneously determine the magnitude of the spin, the magnetic anisotropy and the Kondo properties of individual magnetic atoms on a surface. We find that a Kondo resonance emerges for large-spin atoms only when the magnetic anisotropy creates degenerate ground-state levels that are connected by the spin flip of a screening electron. The magnetic anisotropy also determines how the Kondo resonance evolves in a magnetic field: the resonance peak splits at rates that are strongly direction dependent. These rates are well described by the energies of the underlying unscreened spin states.

Original languageEnglish
Pages (from-to)847-850
Number of pages4
JournalNature Physics
Issue number11
StatePublished - Nov 2008

Bibliographical note

Funding Information:
We thank M. F. Crommie, D. M. Eigler, A. C. Hewson, B. A. Jones, J. E. Moore and J. M. van Ruitenbeek for discussions and B. J. Melior for technical assistance. A.F.O. acknowledges support from the Leiden University Fund; M.T. from the Swiss National Science Foundation; K.v.B. from the German Science Foundation (DFG Forschungsstipendium); S.L. from the Alexander von Humboldt Foundation; C.F.H. from the Engineering and Physical Sciences Research Council (EPSRC) Science and Innovation Award and M.T., C.P.L. and A.J.H. from the Office of Naval Research. H.B. acknowledges EPFL for supporting his sabbatical stay with IBM.


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