Transcript Electron States in Magnetic and Non

Exchange splitting in electronic states of
single atoms and magnetic coupling in
single dimers and trimers on a surface
Mats Persson(1), Hyo-June Lee(2), and Wilson Ho(2)
(1)Dept.
(2)Dept.
of Applied Physics, Chalmers/Göteborg University, SWEDEN
of Physics and Astronomy and Dept. of Chemistry , University of
California, Irvine, USA
Outline
Tunneling spectra with a non-magnetic tip and
density functional calculations of:
• Non-magnetic Au atom and dimer on
NiAl(110) surface
• Magnetic Co, Fe, Mn atoms and dimers,
and Fe trimer on NiAl(110) surface
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N. Nilius, T. M. Wallis, M. Persson, and W. Ho., Phys. Rev. Lett. 90, 196103 (2003)
H. J. Lee, W. Ho, and M. Persson, Phys. Rev. Lett. 92, 186802 (2004)
Non-magnetic Au atom and dimers on a
NiAl(110) surface
• STS of Au adatom and ad-dimers.
• Density functional calculation (PAW-GGA) VASP
Au Adatom and Ad-dimers*
*
Nilius, Wallis, Persson, and Ho, Phys. Rev. Lett. 90, 196103 (2003)
Tunneling Spectra and Images of an
Au Ad-dimer
Density Functional Calculations:
Au Adatom and Ad-dimers
PW-PAW-GGA (VASP)
Adatom
Ad-dimer
Au Adatom
Au Ad-dimer
Resonance Energy Splittings of
Dimers
Magnetic atoms, dimers and trimer
on a NiAl(110) surface*
• STS of Co, Fe, and Mn adatoms and ad-dimers
and Fe ad-trimer
• Density functional calculation (PAW-GGA) VASP
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*H. J. Lee, W. Ho, and M. Persson, Phys. Rev. Lett. 92, 186802 (2004)
Magnetic adatoms at 17 K
Calculated Magnetic Adatom DOS
Two Level System with a Spin
Non-magnetic
Ferromagnetic
Anti Ferromagnetic
Magnetic Co and Fe Addimers: LDOS
Co2/NiAl(110)
E0(AFM)-E0(FM) = 0.42eV
Fe2/NiAl(110)
E0(AFM)-E0(FM) = 0.45eV
m = 3.5mB
m = 5.9mB
Strong adatom-adatom interaction
Interadatom distance (d = 2.2 Å) shorter than bridge-bridge distance (2.9 Å)
Magnetic Mn Addimer: LDOS
E0(AFM)-E0(FM) = 0.036eV
m = 8.9mB
Weak adatom-adatom interaction
Interadatom distance (d = 3.0 Å) close to the bridge-bridge distance (2.9 Å)
Magnetic Fe Ad-trimer
m = 9.5mB
Concluding Remarks
• Unoccupied Kohn-Sham states give a useful
approximation and physical insights of tunneling
spectra of resonances in atom nanostructures on
NiAl(110)
• Non-Kondo resonance signatures of the spin state
in magnetic adatoms, ad-dimers and ad-trimer
Acknowledgements
Experiments:
Niklas Nilius and Mitch Wallis, UC Irvine, USA
Theory:
Doug Mills and Ruqian Wu, UC Irvine, USA
R. Bechara Muniz, Univ. Federal Fluminense, Niteroi, Brazil
Funding: