Dresden 2009 – scientific programme
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MA: Fachverband Magnetismus
MA 4: Surface Magnetism I
MA 4.6: Talk
Monday, March 23, 2009, 12:15–12:30, HSZ 403
The role of magnetic anisotropy in the Kondo effect — •Markus Ternes1,2, Alexander F. Otte1,3, Kirsten v. Bergmann1,4, Sebastian Loth1, Harald Brune1,5, Christopher P. Lutz1, Cyrus P. Hirijbehedin1,6, and Andreas J. Heinrich1 — 1IBM Almaden Research Center — 2MPI Stuttgart — 3NIST Gaithersburg — 4University of Hamburg — 5EPF Lausanne — 6London Centre for Nanotechnology
Using a STM to assemble magnetic structures on a thin insulator, we found that the spin of the atom is influenced by the magnetocrystalline anisotropy of the supporting surface which lifts the spin degeneracy of the ground state and enables the identification of individual atoms by using inelastic electron tunneling spectroscopy [1]. Changes in the observed spectra as a magnetic field was applied along different directions yielded the magnetic anisotropy for individual magnetic atoms [2].
Atoms with half-integer spin remain always degenerated at zero field due to Kramers theorem. We found that if these states differ by an orbital momentum of Δ m=±1 the localized spin is screened by the surrounding conducting electrons of the non-magnetic host and form a Kondo resonance close to the Fermi energy at sufficiently low temperature. Applying a magnetic field splits this Kondo resonance at rates that are strongly direction-dependent, which are well-described by the energies of the underlying unscreened spin states [3].
[1] A. J. Heinrich et al., Science 306, 466 (2004).
[2] C. F. Hirjibehedin et al., Science 317, 1199 (2007).
[3] A. F. Otte et al., Nature Physics 4, 847 (2008).