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Exchange splitting in electronic states of single atoms and magnetic coupling in single dimers and...

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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. of Applied Physics, Chalmers/Göteborg University, SWEDEN (2) Dept. of Physics and Astronomy and Dept. of Chemistry , University of California, Irvine, USA
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Page 1: 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.

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. of Applied Physics, Chalmers/Göteborg University, SWEDEN

(2)Dept. of Physics and Astronomy and Dept. of Chemistry , University of California, Irvine, USA

Page 2: 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.

Outline

• Non-magnetic Au atom and dimer on NiAl(110) surface

• Magnetic Co, Fe, Mn atoms and dimers, and Fe trimer on NiAl(110) surface

Tunneling spectra with a non-magnetic tip and density functional calculations of:

______________________________________________________________________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)

Page 3: 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.

Non-magnetic Au atom and dimers on a NiAl(110) surface

• STS of Au adatom and ad-dimers.• Density functional calculation (PAW-GGA)

VASP

Page 4: 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.

Au Adatom and Ad-dimers*

* Nilius, Wallis, Persson, and Ho, Phys. Rev. Lett. 90, 196103 (2003)

Page 5: 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.

Tunneling Spectra and Images of an Au Ad-dimer

Page 6: 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.

Density Functional Calculations: Au Adatom and Ad-dimers

PW-PAW-GGA (VASP)

Adatom Ad-dimer

Page 7: 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.

Au Adatom

Page 8: 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.

Au Ad-dimer

Page 9: 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.

Resonance Energy Splittings of Dimers

Page 10: 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.

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

___________________________________________________________*H. J. Lee, W. Ho, and M. Persson, Phys. Rev. Lett. 92, 186802 (2004)

Page 11: 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.

Magnetic adatoms at 17 K

Page 12: 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.

Calculated Magnetic Adatom DOS

Page 13: 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.
Page 14: 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.

Two Level System with a Spin

Ferromagnetic Anti FerromagneticNon-magnetic

Page 15: 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.

Magnetic Co and Fe Addimers: LDOS

Co2/NiAl(110)

E0(AFM)-E0(FM) = 0.42eV

Strong adatom-adatom interaction Interadatom distance (d = 2.2 Å) shorter than bridge-bridge distance (2.9 Å)

Fe2/NiAl(110)

E0(AFM)-E0(FM) = 0.45eV

Page 16: 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.

Magnetic Mn Addimer: LDOS

E0(AFM)-E0(FM) = 0.036eV

Weak adatom-adatom interaction Interadatom distance (d = 3.0 Å) close to the bridge-bridge distance (2.9 Å)

Page 17: 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.
Page 18: 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.

Magnetic Fe Ad-trimer

Page 19: 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.

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

Page 20: 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.

AcknowledgementsExperiments: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:


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